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The stability of EMG median frequency under
different muscle contraction conditions and
following anterior cruciate ligament injury
A thesis submitted in fulfillment of the requirements for
the award of
Doctor of Philosophy
Submitted by:
Che Tin Raymond Li
GradDipPhy (UK), MCSP (UK), M Phil (HK)
Centre for Health Research School of Human Movement Studies
Queensland Universi ty of Technology
2004
2
Keywords Electromyography
Median frequency
Anter ior cruciate l igament in jury
Bone pate l lar- tendon bone reconstruct ion
Semitendinosus and graci l is tendon reconstruct ion
Rehabi l i tat ion
Isokinet ic exercise
Open and closed kinet ic chain exercise
Quadriceps avoidance gai t
Muscle atrophy
Type I and type I I muscle f ibres
3
Abstract
Musculoskeletal in jur ies are commonly associated wi th muscle
atrophy as a funct ion of immobi l izat ion or change of normal funct ion.
For example, in jur ies to the anter ior cruciate l igament (ACL) which
may involve l igament reconstruct ion, resul ts in the “quadr iceps
avoidance” gai t which leads to atrophy of the knee extensor
muscles. In these si tuat ions i t is not c lear whether or not the
atrophy is associated with loss of speci f ic muscle f ibre types with
accompanying funct ional def ic i ts. Such knowledge would be helpful
in implement ing exercise regimes designed to compensate for loss of
part icular f ibre types. I t is bel ieved that isokinet ic exercise
performed at speeds below 180° per second strengthens type I
muscle f ibres, and type I I f ibres at fast speeds. However, there is
no evidence to indicate the speci f ic muscle f ibre response to
di f ferent rates of muscle contract ion. Ident i f icat ion of muscle f ibre
type is most di rect ly determined by biopsy technique but is too
invasive for a rout ine measurement. Electromyography median
frequency has been used as a non- invasive measure to infer muscle
f ibre composi t ion in var ious studies. However, the rel iabi l i ty and
accuracy of th is technique has been quest ioned and improvement is
necessary.
This research was designed to provide a more accurate and rel iable
protocol for the determinat ion of EMG median f requency which may
be used, af ter val idat ion against more direct b iopsy techniques, as a
rout ine method for inferr ing muscle f ibre composi t ion. The
invest igat ion also explored the muscular response as measured by
4
EMG median frequency to varying speeds of muscle contract ion,
fat iguing exercise and atrophy fol lowing ACL reconstruct ion. The
ul t imate aim of th is research was to improve the rel iabi l i ty of the
determinat ion of EMG median f requency to enhance i ts appl icat ion
as a predictor of muscle f ibre composi t ion. This provides
informat ion which may improve ACL rehabi l i tat ion programs
designed to restore and prevent speci f ic muscle f ibre types loss that
have not previously been targeted by current rehabi l i ta t ion
programs. This research was conducted in three studies.
Study one determined the stabi l i ty of the EMG median
frequency bi lateral ly for the quadr iceps and hamstr ings muscles and
ident i f ied the mode of contract ion associated with the greatest
rel iabi l i ty . The strength and EMG median f requency of the vastus
lateral is, medial hamstr ings and vastus medial is of 55 subjects was
determined across 5 speeds from 0° to 240° per second using a Kin-
Com isokinet ic dynamometer and an EMG data acquis i t ion system.
Isometr ic contract ion was found to have the least bi lateral
d iscrepancy (4.01% ±3.06) and between t r ia ls standard deviat ion
(4.50) in the vastus lateral is, medial hamstr ings and vastus medial is .
Study two invest igated the EMG median frequency changes in
the vastus lateral is which occur immediately fo l lowing di f ferent
speeds of isokinet ic exercise to the point of fat igue in normal
subjects. Thir ty- four subjects part ic ipated in the study, and
performed a 90-second per iod of isokinet ic exercise to act ivate the
knee extensors at e i ther 30° or 300° per second. EMG median
frequency of the vastus lateral is was determined before, immediately
5
after and 7 minutes af ter the fat iguing exercise. The percentage
drop in EMG median f requency of the vastus medial is was
signi f icant ly (p<0.05) greater af ter s low speed (27.9%) than fast
speed (20.25%) exercise, whi le no signi f icant di f ference was found
for the percentage drop in extension torque. Ful l recovery was
found 7 minutes af ter the fat iguing exercise. By reference to
previous research showing a relat ionship between EMG median
frequency and muscle f ibre type, an increase in act ivat ion of type I
muscle f ibres wi th s low speed exercise and an increase in type I I
muscle f ibres wi th fast speed exercise was observed.
Study three ident i f ied the changes in EMG median frequency
fol lowing ACL reconstruct ion and evaluated the bi lateral d i f ferences
in EMG median f requency of the knee muscles. The relat ionships
between EMG median f requency and the measures of knee funct ional
abi l i ty , knee muscle strength, age and t ime since surgery were a lso
invest igated. Twelve subjects who had undergone ACL
reconstruct ion using a semitendinosus and graci l is graf t 6 to 12
months ear l ier , part ic ipated in the study. EMG median f requency
was determined from an 8-second isometr ic contract ion and knee
funct ional abi l i ty was assessed using the Cincinnat i Rat ing Scale.
Bi lateral EMG median frequency shi f ts were inconsistent among
subjects. On the basis of previous research which indicated a
relat ionship between EMG median frequency and f ibre type, no
consistent pattern of muscular f ibre type atrophy subsequent to ACL
reconstruct ion occurred with in 6 to 12 months (ranged from –43 to
57 Hz). Addi t ional ly, no signi f icant correlat ions were found between
the EMG median frequency and the knee funct ional score and knee
6
extension and f lexion torques, age, t ime since operat ion and the
bi lateral d i f ferences in EMG median frequency. The resul ts of th is
invest igat ion wi l l serve to improve the rel iabi l i ty of EMG median
frequency across a range of condi t ions in which i t has been
evaluated. Further research is needed to conf i rm the re lat ionship
between EMG median frequency and direct observat ions of muscle
f ibre composi t ion to improve the predict ive value of th is measure.
Fol lowing th is val idat ion i t wi l l be possible to evaluate the bi lateral
EMG median f requency shi f t to infer the type of muscle f ibre atrophy,
and use this measure in determining the ef f icacy of speci f ic
rehabi l i tat ion programs.
In conclus ion
• An 8-second isometr ic contract ion is recommended for
determining EMG median frequency.
• EMG median frequency of a muscle decreases signi f icant ly
more af ter s low fat iguing exercise than af ter fast speed
fat iguing exercise. • There was no general ised bi lateral EMG median frequency shi f t
found in a group of subjects 6 to 12 months fol lowing
semitendinosus and graci l is graf t ACL reconstruct ion. • The resul ts of th is study wi l l serve to improve the rel iabi l i ty of
procedures used to determine EMG median frequency under a
range of di f ferent contract i le condi t ions. The EMG median
frequency changes in response to these condi t ions require
further val idat ions with muscle biopsy in future.
7
Table of Contents
T i t le Page ………………………………………………………………….
Cert i f icate …………………………………………………………………
Keywords ………………………………………………………………….
Abstract ……………………………………………………………………
Table of Content ………………………………………………………..
L ist of Figures…………………………………………………………….
List of Tables ………………………………………………………….…
Statement of Or iginal Authorship ……………………………….…
Abbreviat ions …………………………………………………………….
Acknowledgments ………………………………………………………
1
2
3
4
8
18
19
20
Chapter One: Introduction
22
1.1 Preface ……………………………………………………………. 1.2 Rationale ………………………………………………………….
1.2.1 Rel iabi l i ty in the determinat ion of EMG median f requency ………………………………………………….
1.2.2 EMG median f requency changes under varying condi t ions of muscle contract ions …………………
1.2.3 EMG median f requency changes in knee muscles fo l lowing ACL reconstruct ion ……………………….
1.3 Objective ……………………………………………………………
22
23
23
25
26
28
Chapter Two: Literature Review
30
2.1 Electromyography ……………………………………………….. 2.1.1 The use of median f requency to determine muscle
f ibre composi t ion …………………………………..….. . 2.1.2 Methods of measurement of muscle f ibre type…….
The biopsy technique The Mechanomyography (MMG)
2.1.3 Isometr ic contract ion durat ion ……………………….. 2.1.4 Rel iabi l i ty of determining EMG median
frequency.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 The anterior cruciate l igament …………………………….. 2.2.1 Muscular adaptat ion fol lowing ACL reconstruct ion
The rehabi l i tat ion of ACL in jury or reconstruct ion
30
30 39
43
45
51
51
8
2.2.2 The importance of the hamstr ings and quadr iceps rat io in the rehabi l i tat ion of ACL in jury and reconstruct ion ……………………... . . . . . . . . . . . . . . . . . . . . . . . .
2.2.3 Funct ional abi l i ty of the ACL reconstructed knee
2.3 The role of isokinetic technology in ACL rehabil i tation 2.3.1 Select ive muscle f ibre t ra ining in isokinet ic
movements ……………………………………………… 2.3.2 The appl icat ion of isokinet ic technology to control
muscle contract ion veloci ty dur ing ACL rehabi l i tat ion ……………………………………………
2.4 Summary ……………………………………………………………
55 56
62
62
65
68
Chapter Three: Evaluation of the reliability of EMG median frequency measured isometrically and isokinetically
69
3.1 Introduction ……………………………………………………….. 3.2 Methodology ……………………………………………………….
3.2.1 Subjects ………………………………………………….. 3.2.2 Exper imental procedure ……………………………….
The evaluat ion protocol ………………………………. Consent and screening ……………………………….. EMG median f requency determinat ion Procedure ……………………………………………….. Calculat ion of b i lateral d iscrepancy ………………. Isokinet ic test ing protocol …………………………..
3.2.3 Stat ist ical analysis ……………………………………..
3.3 Results ……………………………………………………………. 3.3.1 EMG median f requency ……………………………….. 3.3.2 Gender and bi lateral EMG median frequency
comparison ……………………………………………….. 3.3.3 Between t r ia l standard deviat ion of EMG median
frequency within a bout of muscle test ing …………
3.4 Discussion and summary …………………………………….
69
74
74 74 75
76 79 79
81
91
91
92
92
98
Chapter Four: EMG median frequency changes of vastus lateralis in response to different speeds of fatiguing exercise
105
4.1 Introduction ……………………………………………………… 4.2 Methodology ……………………………………………………….
4.2.1 Subjects ……………………………………………………
4.2.2 Exper imental procedure ………………………………
105
108
108
109
9
Consent and screening ……………………………….. The exper imental protocol ……………………………
4.2.3 Stat ist ical analysis ……………………………………..
4.3 Results ……………………………………………………………. 4.4 Discussion and summary …………………………………….
109 110
112
112
118
Chapter Five: EMG median frequency changes of the knee muscles subsequent to anterior cruciate ligament reconstruction
126
5.1 Introduction ………………………………………………………. 5.2 Methodology ………………………………………………………
5.2.1. Subjects ……………………………………………………
5.2.2. Exper imental procedure ……………………………….
EMG evaluat ion and isokinet ic test ing …………… • Evaluat ion of bi lateral d iscrepancy of EMG
median frequency ………………………………… • Isometr ic strength test ing …………………….. • Further analysis of resul ts………………………
5.2.3. Stat ist ical analysis …………………………………….
5.3 Results …………………………………………………………… 5.3.1. The EMG median frequency ………………………….
Comparison of bi la teral d iscrepancy of EMG median frequency of the ACL reconstructed subjects …………………………………………………… The EMG median frequency shi f t of the ACL reconstructed subjects ………………………………..
5.3.2. Knee funct ional capabi l i ty ……………………………
5.3.3. Isometr ic torque …………………………………………
The knee f lexor and knee extensor strength rat io Bi lateral d iscrepancy …………………………………..
5.3.4. Relat ionship between funct ional measures and shi f t in EMG median f requency …………………….
5.4 Discussion and summary …………………………….………
5.4.1. EMG median f requency ……………………………..….
The comparison between the ACL reconstruct ion subjects and subjects of Study One ……………..…. The use of the contralateral l imb as a control to the ACL reconstructed l imb …………………………. Bi lateral EMG median f requency di f ferences and shi f t o f ACL reconstructed subjects ………………
126
129
130
131
132
133 134 135
135
136
136
136
137
137
137
138 138
139
145
147
147
148
149
10
5.4.2. The knee funct ional abi l i ty score ……………….……
5.4.3. Isometr ic strength of the knee muscles ……….……
5.4.4. Correlat ion ……………………………………………….
Correlat ion between the bi lateral st rength discrepancy and bi lateral EMG frequency shi f t . . . . Correlat ion between the funct ional abi l i ty and other measures ………………………………………….
152
154
156
156
158
Chapter Six: General discussion, summary and conclusions
163
6.1 General discussion …………………………………………… 6.2 Summary and Recommendation…... . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Conclusion ……………………………………………………… 6.4 Recommendation for further studies ……………………
163
170
174
180
Bibliography
181
Appendices
203
A. Raw data for indiv idual subjects and addi t ional graphical representat ion of group data and stat ist ical informat ion for Study One …………………………………………………………... .
B. Ethics Approvals ………... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .… C. Subject recrui tment informat ion mater ia ls for Studies One,
Two and Three ……………………………………………………… D. Subject in format ion package and Consent forms.. . . . . . . . . . . . . .
E. The Cincinnat i Rat ing System Scoring Sheet (Modif ied)…..
F. Other forms and informat ion …………………………………….
G. Publ icat ions and presented papers ….. .………………………
205 238
242 248
252
255
260
11
List of Figures
Chapter Three
Fig 3.1 A pre-ampl i f ied electrode connected to the AmLab EMG Acquisi t ion System via a Qantec Ampl i f ier .
82
Fig 3.2 A pre-ampl i f ied bipolar surface electrode used in
al l three studies.
82
Fig 3.3 Placement of pre-ampl i f ied bipolar surface electrode for r ight vastus lateral is.
83
Fig 3.4 Placement of pre-ampl i f ied bipolar surface electrode for lef t medial hamstr ings.
83
Fig 3.5 Placement of pre-ampl i f ied bipolar surface electrode for lef t vastus medial is.
83
Fig 3.6 A typical EMG test record showing the jo int angle, the EMG signal and the torque of the vastus lateral is in the f i rst , second and third rows respect ively.
84
Fig 3.7 Direct EMG signal f rom vastus lateral is showing the procedure to detect the segment wi th the highest value.
85
Fig 3.8 A typical f requency distr ibut ion curve produced by FFT.
86
Fig 3.9 Dif ferent stages in the determinat ion of median frequency from direct EMG signals.
87
Fig 3.10 Schematic diagram showing the EMG median frequency transformat ion process from raw EMG signals.
88
Fig 3.11 A typical raw EMG signal generated from a 60º/second isokinet ic extension and f lexion contract ion using the Kin-Com dynamometer.
89
Fig 3.12 A typical EMG MF graph showing the bi la teral d iscrepancy.
90
Fig 3.13 Mean bi lateral d iscrepancy of EMG median frequency (MF) of VL, MH and VM of al l subjects at d i f ferent speeds.
96
Fig 3.14 Between t r ia ls standard deviat ion (BTSD) of EMG median f requency of VL, MH, and VM of al l subjects at d i f ferent speeds.
96
12
Fig 3.15 Percentage bi latera l d iscrepancy (%BD) in EMG MF of a l l muscles in male and in female subjects at d i f ferent speeds.
97
Fig 3.16 Between t r ia ls standard deviat ion of EMG MF of al l muscles of the non-dominant and dominant l imbs of a l l subjects at d i f ferent speeds.
97
Fig 3.17 Between t r ia ls standard deviat ion of EMG MF of al l muscles of male and female subjects at d i f ferent speeds.
97
Chapter Four Fig 4.1 Percentage differences in pre and post measures of
EMG MF and torque in relation to fast and slow exercise to fatigue of all subjects.
117
Fig 4.2 Percentage of recovery in EMG MF and torque in relat ion to fast and slow exercise to fat igue of a l l subjects.
117
Chapter Five Fig 5.1 EMG MF in Hz of the VL, MH and VM of lef t l imb of
normal subjects, the contralateral and the reconstructed l imbs of the ACL subjects.
140
Fig 5.2 Percentage bi lateral d iscrepancy in the EMG MF of the VL, MH and VM of normal subjects and ACL reconstructed subjects.
140
Fig 5.3 Relat ive isometr ic strength of the hamstr ings and quadr iceps of the contralateral l imb and the reconstructed l imbs of the ACL reconstruct ion subjects.
141
Fig 5.4 The EMG MF shi f t of the VM, VL and MH of ACL reconstructed l imb measured isometr ical ly and taking the contralateral l imb as a zero reference point .
141
13
Chapter Six Fig 6.1 Schematic presentat ion of a suggested ACL
rehabi l i tat ion protocol using f indings ar is ing out of the research.
173
14
List of Tables Chapter Three Table 3.1 Mean EMG MF in Hz and the mean %BD of VL, MH
and VM combined for al l subjects at d i f ferent speeds.
94
Table 3.2 Mean EMG MF in Hz and the mean %BD of VL, MH and VM of al l subjects at d i f ferent speeds.
94
Table 3.3 Mean EMG MF in Hz and the standard deviat ion of VL, MH and VM of male and female subjects at d i f ferent speeds.
95
Table 3.4 Mean %BD and the standard deviat ion of EMG MF of VL, MH and VM of male and female subjects at d i f ferent speeds.
95
Chapter Four Table 4.1 The mean of the di f ferences in pre and post values of
EMG MF fol lowing fat iguing exercises expressed in percentages.
113
Table 4.2 The mean of the percentage decrease and recovery of EMG MF of the vastus lateral is and of the extension torque of a l l subjects.
114
Table 4.3 The mean (±SD) values of the pre-fat iguing exercise EMG MF of the VL of male, female and al l subjects.
114
Chapter Five Table 5.1 Mean of the EMG MF in Hz of the VL, MH and VM of
the contra lateral and the ACL reconstructed l imbs.
142
Table 5.2 Mean of the knee funct ional scores using the Cincinnat i Rat ing System of the ACL reconstructed subjects.
142
Table 5.3 Mean of the isometr ic torque of the knee extensors and knee f lexors and the H:Q rat ios of the ACL reconstructed subjects.
142
15
Table 5.4 Mean of the Cincinnat i knee funct ional score, bi lateral d iscrepancy of the EMG MF and % BD of knee extension and knee f lexion st rengths of the ACL reconstructed subjects.
142
Table 5.5 Mean values for age, post-operat ive durat ion, EMG MF of the medial hamstr ings of the contralateral l imb and the EMG MF of the vastus medial is of the ACL reconstructed l imb when subjects were grouped according to the higher and lower funct ional sub-groups.
143
Table 5.6 Mean values for age when subjects were grouped according to the larger and smal ler bi lateral torque di f ference in knee extension and knee f lexion.
143
Table 5.7 Mean values for EMG MF shi f t in Hz of the medial hamstr ings when subjects were grouped according to the direct ion of EMG MF shi f t of the vastus lateral is and vastus medial is .
144
16
I , Che Tin Raymond Li , a candidate for the degree of Doctor of
Phi losophy at Queensland Universi ty of Technology, have not been
enrol led for another ter t iary award dur ing the term of my PhD
candidature wi thout the knowledge and approval of the Universi ty ’s
Research Degree Commit tee.
Signature:
Date: 30t h November 2004
17
The Statement of or ig inal authorship
The work contained in th is thesis has not been previously
submit ted for a degree or d iploma at any other higher educat ion
inst i tu t ion. To the best of my knowledge, the thesis contains no
mater ia l previously publ ished or wr i t ten by another person except
where due reference is made.
Signature:
Date: 30t h November 2004
18
Abbreviations °/s Degree per second
ACL Anter ior cruciate l igament
ACLHQ The hamstr ing and quadr iceps rat io of the ACL
reconstructed l imb
ACLR Anter ior cruciate l igament reconstruct ion
%BD Percentage bi lateral d iscrepancy
BPTB Bone pate l lar- tendon bone
BTSD Between t r ia ls standard deviat ion
CKC Closed kinet ic chain
CPM Cont inuous passive movement
EMG Electromyography
Ext Extension
FG Extension torque of the fast group
Flex Flexion
FMF EMG MF of the fast exercise group
FFT Fast Four ier Transformat ion
FT/ST Fast twi tch / Slow twi tch
H:Q Relat ive strength of hamstr ings to quadr iceps
Hz Hertz
MF Median frequency
MH Medial hamstr ings
NormHQ The H:Q rat io of the contralateral l imb
OKC Open kinet ic chain
PAR-Q Physical Act iv i ty Readiness Quest ionnaire
RMS Root mean squares
SD Standard deviat ion
SG Extension torque of the s low group
SMF EMG MF of the slow exercise group
STG Semitendinosus and graci l is
T Torque
VL Vastus lateral is
VM Vastus medial is
19
Acknowledgement:
I would l ike to show my deepest appreciat ion to the fol lowing
people:
Professor Anthony W Parker, my pr incipal supervisor, for h is
supervis ion, f r iendship and support throughout the per iod of the
study.
Dr James Smeathers, my associate supervisor, for h is guidance
and supervis ion throughout the per iod of the study.
Dr Peter Myers and his staf f team in provid ing ACL def ic ient
subjects; and Mr Adam Bryant for h is f r iendship, support and
construct ive suggest ions on many aspects of my study, part icular ly
in EMG data management.
Mr Peter Condie for his assistance in al l the EMG data analysis
and his technical support in the equipment used in the study. Ms
Connie Ng for her assistance in my study.
Al l the subjects, both normal and ACL def ic ient , for thei r
f r iendship, support and commitment in the studies.
Al l my peers, academic and general staf f members of the
School of Human Movement Studies. I would l ike to part icular ly
ment ion here: Dr Michael McDonald, Dr Jarrod Meerk in, Dr Tom
20
Cuddihy, Dr Ian Stewart , Mr. Mart in Gregg, Mrs. Connie Wishart ,
and Mrs. Pam Smith.
I would l ike to thank my fami ly members who are in New
Zealand in part icular, my brother- in- law Dr Ken Fung and my dear
s ister Mrs May Fung, who have been looking af ter my mother wi thout
any complaints whi le I was away from home doing my study in
Br isbane.
I would l ike to thank my wi fe, Peggy for her love, support and
pat ience throughout al l these long years of f rustrat ion and hardship
dur ing my study.
Above al l , the t rue support behind me is f rom Jesus Christ the
Lord my Savior who has given me a new l i fe to l ive. May He be
glor i f ied.
21
Chapter one
Introduction
1.1 Preface
Invest igat ion of muscle f ibre composi t ion is rout inely conducted by
histological analysis of muscle biopsies. The technique has been
used to ident i fy changes in muscle f ibre type fol lowing var ious
exercise rout ines and to invest igate atrophic changes as a funct ion
of d isuse or in jury. However, whi le th is technique is considered
accurate and rel iable, i t is too invasive a procedure for rout ine
assessment, part icular ly when large number of subjects are
involved. Therefore, the development of a non- invasive procedure
which may be rout inely used in t ra ining or c l in ical pract ice has been
a matter of pr ior i ty and has st imulated examinat ion of the use of
e lectromyography (EMG) median frequency as an al ternat ive method
for the predict ion of muscle f ibre type composi t ion (McNair and
Wood, 1993). Al though the method has shown promise, i ts accuracy
in predict ing muscle f ibre composi t ion and i ts val id i ty against the
more direct b iopsy technique has received insuff ic ient invest igat ion.
Addi t ional ly, as a f i rst stage in the val idat ion process i t is important
to establ ish the stabi l i ty of the measure of median f requency which
may show considerable var iance under di f ferent condi t ions of
muscle contract ion. The rel iabi l i ty of EMG median frequency in
predict ing muscle f ibre type has been quest ioned (Kupa et a l . , 1995,
McHugh et al . , 2002a) possibly as a funct ion of lack of control over
22
the rel iabi l i ty of th is measure under di f ferent condi t ions and
inadequate evaluat ion of i ts s tabi l i ty .
1.2 Rationale of the studies
1.2.1 Reliabil i ty of EMG median frequency
Previous studies have shown a direct re lat ionship between the EMG
median f requency and conduct ion veloci ty of a muscle (Biedermann
et al . , 1990, DeLuca, 1985, Masuda et al . , 2001). Dur ing a
sustained contract ion, changes in EMG median frequency and
conduct ion veloci ty have been associated with muscle f ibre
composi t ion as determined by muscle biopsy techniques (Kupa et
a l . , 1995). This impl ies that EMG median frequency may ref lect
muscle f ibre conduct ion veloci ty and a change in the EMG median
frequency can be interpreted as a change in conduct ion veloci ty of
the muscle f ibre (McNair and Wood, 1993). Conduct ion veloci ty and
EMG median frequency have been shown to be correlated (r=0.87)
and are higher in fast twi tch than in s low twi tch muscle f ibres (Kupa
et al . , 1995). Hence i t is proposed that EMG median frequency may
be used as an indicator of the dominant muscle f ibre type in a
part icular muscle.
However, greater use of EMG median frequency for the predict ion of
muscle f ibre type is l imi ted at th is t ime by the lack of informat ion
concerning the ef fect of d i f ferent var iables on the rel iabi l i ty of the
measure (McHugh et al . , 2002b). One of the main issues is the
select ion of the most appropr iate mode required to accurately and
23
rel iably determine EMG median frequency (McHugh et al . , 2002b).
Di f ferent modes of muscle contract ion are associated with
di f ferences in muscle length, to which the EMG median frequency is
sensi t ive (Potvin, 1997, Bazzy et a l . , 1986). Al though concentr ic,
eccentr ic or isometr ic modes of muscle contract ions have been used
to determine EMG median frequency (McNair and Wood, 1993,
Koumantakis et a l . , 2001a, Pincivero et a l . , 2000), muscle length
has not been wel l control led and inaccurate resul ts may have been
produced. McHugh et al . (2000) suggested that the isometr ic mode
of exercise may increase the rel iabi l i ty of EMG median frequency but
fur ther research in th is area is required to conf i rm or reject th is
hypothesis. Another important concern in the use of EMG median
frequency relates to the rel iabi l i ty and stabi l i ty of the measure over
t ime. Previous studies have only evaluated the reproducibi l i ty of
EMG median frequency on separate occasions (bouts) rather than
successive contract ions (Bi lodeau et a l . , 1994, Ng et a l . , 1996,
Koumantakis et a l . , 2001b, McHugh et al . , 2001, Dedering et al . ,
2000, Taylor et a l . , 1997a). There is a need for a more rel iable
procedure in determining EMG median frequency.
In addi t ion, an assumption was made on the basis of previous
research, that the EMG median frequency of a muscle f ibre is
bi lateral ly equal when appl ied to the measurement of conduct iv i ty
(McNair and Wood 1993, Kupa et al . , 1995, Roy et al . , 1989,
McHugh et al . , 2002b) and when used as an indicator of fat igue
(Dedering et a l . , 2000, Ng et al . , 1996, Lowery et a l . , 2002). This
assumption however requires scient i f ic conf i rmat ion.
24
1.2.2 EMG median frequency changes under varying condit ions
of muscle contractions
There is evidence to suggest that isok inet ic exercise is an ef fect ive
mode of resistance training in the restorat ion of muscle strength in
pat ients wi th an ACL injury (McNair and Wood, 1993, Sargeant et
a l . , 1994, Li et a l . , 1996, Haut ier et a l . , 1996). An advantage of
isokinet ic dynamometers is their abi l i ty to provide a range of
contract ion speeds which is general ly important in target ing speci f ic
types of muscle f ibres (Grimby, 1985). The meri t of isokinet ic
technology in restor ing and prevent ing a speci f ic type of muscle
f ibre atrophy has been widely establ ished (Kannus, 1994, Esselman
et al . , 1991, Cote et al . , 1988, Smith and Melton, 1981). In contrast ,
the t radi t ional weight t ra in ing exercises incorporat ing isotonic and
isometr ic muscle act ions lack the choice of speeds required to
prevent atrophy of a speci f ic populat ion of muscle f ibre wi thin the
muscle. Consequent ly, exercis ing in these modes does not easi ly
target a speci f ic type of muscle f ibre and may not sat isfy the
requirements of ACL in jury rehabi l i tat ion in which atrophic changes
are f ibre type speci f ic (Edstrom, 1970, Nakamura et a l . , 1984).
Isokinetic technology can provide a wide continuum of speeds from 0°
to 450° per second for testing and rehabil i tation purposes (Li et al.,
1996, Timm et al., 1988, Ellenbecker et al., 1988). These programs
use two or more isokinetic training speeds in order to improve the
strength of both muscle f ibre types (Parcell et al., 2002, Kannus,
1994). Generally, isokinetic speeds less than 180° per second (slow
speed) are believed to strengthen slow twitch muscle f ibres, whereas,
25
at fast training speed (greater than 180° per second), fast twitch
muscle f ibres are strengthened (Chan et al., 1996). This classif ication
of slow and fast speeds is a function of the range of speeds provided
by the dynamometer and does not necessari ly reflect the functional
speed of the muscle contraction. At this t ime, there is no evidence
documenting the specif ic type of muscle fibres being activated in
response to different rates of muscular contraction during isokinetic
training at different speeds. As biopsy techniques are too invasive for
this kind of investigation, there is a need for a non-invasive approach
using a reliable EMG median frequency measurement to infer muscle
f ibre composit ion.
1.2.3 Functional adaptation of the knee fol lowing ACL
reconstruction
ACL in jury has been shown to increase anter ior instabi l i ty (Bul ter et
a l . , 1980, Wexler et a l . , 1998). Funct ional ly, th is instabi l i ty can be
diminished by a reduct ion in quadr iceps contract ion which increases
the anter ior t ranslat ion of the t ib ia in relat ion to the femur (Wexler et
a l . , 1998). This can be explained by reference to the biomechanics
of the knee jo int which for opt imum funct ioning requires a balance
between the poster ior moment caused by the contract ion of the
hamstr ings and the anter ior moment generated by the quadr iceps
(Berchuck et al . , 1990).
During the concurrent contraction of these two muscles, a greater
quadriceps force as compared to the hamstrings force wil l result in a
net anterior (quadriceps) moment in the knee joint. This in turn causes
26
greater anterior instabil i ty of the ACL deficient or reconstructed knee.
Previous research has shown that patients with an ACL deficient knee
have a signif icantly lower than normal anterior moment (Arms et al.,
1984, Berchuck et al., 1990) during walking (Andriacchi, 1993). This is
considered a functional adaptation to the anterior instabil i ty and is
referred to as “quadriceps avoidance” gait (Berchuck et al., 1990,
Hurwitz et al., 1997, Devita et al., 1997). One of the characteristics of
“quadriceps avoidance” gait is the development of atrophic changes of
the muscles around the knee. These atrophic changes are f ibre type
dependent (Edstrom, 1970), however, there is inconsistency in the
l i terature with respect to the type of muscle f ibre involved. Some
studies have reported atrophy of type I f ibres following ACL injury
(Edstrom, 1970, Nakamura et al., 1986), whereas others have reported
atrophy of type II muscle fibres after f inding a reduction in the cross-
sectional area of the type II f ibres (Baugher et al., 1984) or a left shift
of the EMG median frequency in the EMG power spectrum (McNair and
Wood, 1993). This left shift can be interpreted as a function of a
decrease in the conduction velocity of the muscle which is to a
preferential atrophy of fast twitch (type II) muscle f ibres. Other
investigators have concluded that type I and type II muscle f ibres are
affected equally fol lowing ACL injury (Gerber et al., 1985). The
diversity in the results makes the type of muscle f ibre atrophy following
ACL injury unclear. Therefore further investigation of the influence of
ACL reconstruction on muscle atrophy with particular emphasis on a
reliable and non-invasive measurement of EMG median frequency is
needed.
27
1.3 Objectives
The invest igat ion was designed to address some of the areas of
def ic iency ident i f ied ear l ier and was conducted in three studies wi th
the fol lowing object ives:
Study One
• To determine the stabi l i ty of the measure of the EMG median
frequency bi lateral ly and across both extensor and f lexor
muscles of the knee.
• To ident i fy the mode of contract ion associated with greatest
rel iabi l i ty of EMG median f requency across 5 speeds from 0 to
240° per second.
• To provide a more accurate and rel iable protocol , af ter
val idat ion studies with the biopsy technique, for use in the
determinat ion of EMG median f requency as a rout ine non-
invasive method to infer muscle f ibre composi t ion, , dur ing
rehabi l i tat ion of the ACL reconstruct ion.
Study Two
• To invest igate changes in EMG median frequency fol lowing
fat iguing f rom both fast and slow speed isokinet ic exercise.
28
Study Three
• To invest igate changes in EMG median frequency 6–12 months
fo l lowing ACL reconstruct ion.
• To invest igate the relat ionship between EMG median f requency
and the degree of post ACL reconstruct ion recovery including
the muscle strength and knee funct ional abi l i ty .
The in i t ia l object ive of the project was to invest igate a rel iable
protocol for the determinat ion of EMG median frequency under
di f ferent condi t ions including isometr ic and isokinet ic modes of
exercise. The evidence from this in i t ia l phase of the study (Study
One) was used to further determine the stabi l i ty of EMG median
frequency in response to di f ferent speeds of exercise (Study Two).
This in format ion was essent ia l for the conduct of Study Three which
appl ied this knowledge of EMG median f requency to the cl in ical
s i tuat ion involving subjects who had underdone ACL reconstruct ion.
29
Chapter Two
Literature Review
2.1 Electromyography
Surface EMG signals normal ly show random waveforms because
they represent a sum of act ion potent ia ls f rom many independent ly
act ivated motor uni ts. I t has been possible to est imate a degree of
muscular act iv i ty based on the average ampl i tude of surface EMGs
(Basmaj ian and De Luca, 1985). The use of the EMG signal is
inf in i te. For example, s ince the 1900s, EMG has been employed
extensively to interpret both funct ional and dysfunct ional muscle
recrui tment patterns (Gregor et a l . , 1991) and muscle act iv i ty
patterns in pat ients wi th gai t d isorders (Yang and Winter, 1984).
More recent ly, EMG signals have been used to provide ins ight in to
musculoskeletal system funct ion v ia est imat ion of muscle f ibre
conduct ion veloci ty. The frequency informat ion in the EMG
spectrum, as a funct ion of change in the conduct ion veloci ty of a
muscle, has also been widely appl ied to assess local ized muscle
fat igue (Roy et a l . , 1989, Ng et a l . , 2002, Arendt-Nielsen and Mi l ls ,
1988) and determine muscle f ibre composi t ion (Kupa et al . , 1995).
2.1.1 The use of EMG median frequency to determine muscle
f ibre composition
EMG is an appropr iate tool to measure the relat ive intensi ty of
muscle act ions dur ing exercise and funct ional act iv i t ies (Gryzlo et
30
al. , 1994). In recent years, the invest igat ion of t ime dependent
changes in EMG has been used to assess the funct ional capabi l i t ies
of var ious muscle groups (Biedermann et a l . , 1990, Basano and
Ottonel lo, 1986, De Luca, 1985, Merlet t i et a l . , 1985). EMG
var iables such as the mean frequency, the median frequency and
muscle f ibre conduct ion veloci ty have been widely used part icular ly
in the evaluat ion of fat igue (Basmaj ian and De Luca, 1985, Masuda
et a l . , 2001). These EMG var iables are used not only as indicators
of fat igue but also as a non- invasive means of examining select ive
atrophy of muscle f ibre types (McNair and Wood, 1993).
EMG signals ref lect the funct ional state of a muscle and the
del ineat ion of muscle act ion over t ime dur ing a sustained muscle
contract ion (Masuda et a l . , 2001). I t has been shown that muscles
wi th a high percentage of fast twi tch f ibres have a greater rate of
decrease in the EMG median frequency than muscles wi th a low
percentage of fast twi tch f ibres (Gerdle et a l . , 1991, Komi and
Tesch, 1979, Linssen et a l . , 1991a). I t has also been shown
(Arendt-Nielson and Mi l ls , 1988, Sadoyama et al . , 1983) that
changes in the central tendency measures of the EMG power
spectrum are associated with the conduct ion veloci ty of the muscle
f ibre (McNair and Wood, 1993, Broman et al . , 1985).
Human muscles composed pr imari ly of fast twi tch f ibres have a
greater conduct ion veloci ty than those composed of most ly s low
twi tch f ibres (Linssen et a l . , 1991a). Hence, muscles wi th a greater
proport ion of fast twi tch f ibres are known to have a higher EMG
31
median f requency than those composed predominant ly of s low twi tch
f ibres. This raises the possibi l i ty that the f ibre type composi t ion of a
muscle can be est imated on the basis of EMG spectral parameters
(Gerdle et a l . , 1988, Wret l ing et a l . , 1987). McNair and Wood (1993)
tested this hypothesis and postulated that a change in the median
frequency may be interpreted as a change in the conduct ion veloci ty
and this in turn is related to atrophy or fat igue of a speci f ic muscle
f ibre type.
The hypothesis that the f requency analysis of the EMG signals f rom
a muscle dur ing maximal isok inet ic muscle contract ion can be used
to ident i fy atrophy of a speci f ic muscle f ibre type was examined
using a study of 17 ACL injured subjects (McNair and Wood, 1993).
The mean age of the subjects (8 males and 9 females) was 27 years
and the t ime since their in i t ia l in jury was 20 months. Based on the
magnitude of their b i lateral quadr iceps peak torque def ic i t , subjects
were div ided into two groups, namely a maximal def ic i t group (20.5%
± 2.1%) and a minimal def ic i t group (-1.5% ± 1.65%). The resul ts
showed that in the maximal def ic i t group, the vastus lateral is
muscles of the ACL def ic ient l imb had a s igni f icant ly lower EMG
median f requency than that of the contralateral muscle (p<0.05).
The EMG median frequency of both legs in the minimal def ic i t group
was simi lar to that of the uninvolved l imb of the maximal def ic ient
group. The lowering of the EMG median frequency in the maximal ly
def ic ient group was at t r ibuted to a shi f t in the power spectrum
towards the lef t , which is di rect ly related to the conduct ion veloci ty
of the muscle f ibre (Stulen and De Luca, 1981, Arendt-Nei lson and
Mi l ls 1988, Sadoyama et a l . , 1983). A posi t ive relat ionship between
32
conduct ion veloci ty and muscle s ize has been known for some t ime
(Hakansson 1956 as ci ted in McNair and Wood, 1993) and according
to the “s ize pr inc iple” as descr ibed by Henneman and Olsen (1965),
motor uni ts wi th large muscle f ibres have been shown to be fast
twi tch, and general ly act at greater force levels. According to
DeLuca (1985), these motor uni ts have shorter contract ion t imes,
shorter twi tch durat ions and operate at h igher f i r ing rates. The
lowering of EMG median frequency of the maximal def ic ient group
found in McNair and Wood’s (1993) study was interpreted as being a
funct ion of decreased muscle conduct ion veloc i ty and related to
atrophy of type I I ( fast twi tch) muscle f ibres.
The f indings of th is study were cr i t ic ized in relat ion to the
methodology used (McHugh et al . , 2002a). Interpretat ion of the
resul ts was based on the premise that median frequency pr imari ly
ref lects muscle f ibre conduct ion veloci ty and that conduct ion veloci ty
is h igher in fast twi tch than in s low twi tch muscle f ibres (Hagg et a l . ,
1992, Kupa et al . , 1995). However, conduct ion veloci ty and median
frequency are also sensi t ive to changes in muscle f ibre diameter
independent of f ibre type. Such changes may occur in the muscle
lengthening and shortening which occur dur ing a dynamic concentr ic
contract ion (Potvin, 1997). McHugh and col leagues (2002a) fur ther
suggested that i t was possible that the lower median frequency
obtained from a dynamic contract ion might have ref lected non-
select ive atrophy of a l l f ibres. Previous studies have shown that the
relat ionship between muscle length and surface EMG median
frequency was consistent in isometr ic contract ions (Potvin, 1997,
Mori tani et a l . , 1988, Bazzy et al . , 1986). Therefore, i t was
33
recommended when using EMG median frequency as an indicator of
muscle f ibre atrophy, that isometr ic contract ion would appear to be
the preferred contract ion mode to maintain a more stable muscle
f ibre diameter. The bi lateral comparison of EMG median f requency
has not been extensively studied, however i t has general ly been
shown that under normal s i tuat ions the EMG median f requency in
the quadr iceps of the in jured and contralateral l imb of the ACL
injured subjects are s imi lar (McNair and Wood, 1993, McHugh et al . ,
2001). Simi lar ly, in a study of the EMG median frequency of back
extensor muscles in 16 subjects wi th low back pain, b i lateral
equal i ty was shown in th is measure (Koumantakis et a l . , 2001).
The rel iabi l i ty of using EMG spectral parameters to est imate muscle
f ibre type composi t ion has also been quest ioned based on the
di f f icul ty in control l ing a range of physiological factors (Kupa et al . ,
1995). These include: the muscle contract ion mode classi f ied
according to the change of muscle length dur ing contract ion
(Bi lodeau et al . , 1991, Oberg et a l . , 1987, Shanker et a l . , 1989);
muscle actual length (Potvin, 1997, McHugh et al . , 2002b); muscle
type (biart icular or uniart icu lar) ; shape (bipennate or unipennate);
f ibre direct ion (McHugh et a l . , 2002b, Garret t et a l . , 1984); the pH of
the muscle (Kar lsson et a l . , 2000); temperature (Mori tani et a l . ,
1988, Nedal et a l . , 1972); and the contract ion intensi ty of the muscle
(McHugh et al . , 2002a). Di f ferences inherent in the use of e i ther
f ine wire or surface electrode placement (Kamen and Caldwel l ,
1996) are examples of exper imental factors which may inf luence
EMG recording (Kr iv ickas et a l . , 1996, McHugh et al . , 2002b). The
processing of these signals is a potent ia l source of d iscrepancy,
34
part icular ly in the appl icat ion of the fast Four ier t ransformat ion
(FFT) algor i thm (McHugh et al . , 2002b), or more precisely, the
spat ia l width (Kar lsson et a l . , 2000). Each of these factors have the
potent ia l to inf luence the EMG median frequency and need to be
careful ly control led to del iver re l iable informat ion.
An in-v i t ro invest igat ion using Wistar rats al lowed a wel l control led
evaluat ion of the relat ionship between EMG median frequency, nerve
conduct ion veloci ty and muscle f ibre type (Kupa et a l . , 1995).
Biopsies taken f rom the extensor digi torum longus and the soleus of
the hind l imbs of the animals were used to determine muscle f ibre
types. Muscle preparat ion and st imulat ion procedures were
consistent ly appl ied. EMG signals dur ing contract ions of a 20-
second durat ion were sampled at a rate of 1024 Hz and div ided into
0.5-second epochs. A 20-mi l l isecond window was digi t ized af ter
each st imulated pulse, wi th the f i rst mi l l isecond of each window
el iminated to reduce exper imental errors. EMG median f requency
was calculated by zero padding each average M-wave response to
0.5 second, giv ing a f requency resolut ion of 2 Hz. Al l muscle
samples were analysed using three histochemical processes.
Resul ts showed that muscles wi th a higher percentage of fast twi tch
f ibres had a higher EMG median f requency (r=0.85). This resul t
indicated that the changes in EMG median frequency and the
conduct ion veloci ty dur ing a sustained contract ion were associated
with the muscle f ibre composi t ion. Kupa et a l . (1995) stated that
based on the EMG median frequency, i t was possible to predict
muscle f ibre composi t ion. Furthermore they supported the
possibi l i ty of ut i l iz ing surface EMG techniques to obtain a non-
35
invasive “electrophysiological b iopsy” for est imat ing muscle f ibre
composi t ion, under control led physiological and exper imental
condi t ions.
Recent ly, an in-v ivo study of the quadr iceps muscles in 10 heal thy
men was conducted to compare the frequency content of EMG dur ing
eccentr ic and concentr ic contract ions at var ious intensi t ies (McHugh
et al . , 2002b). Surface electrodes were used because of the
excel lent intra-subject rel iabi l i ty (Linsson et a l . , 1993, Kr iv ickas et
a l . , 1996). In th is study, a 3-second isometr ic contract ion was used
to determine the EMG median frequency. The resul ts showed that
the increase in EMG median frequency was related to the
recrui tment of fast- twi tch motor uni ts. This was consistent wi th the
f indings of the in-vi t ro animal study (Kupa et al . , 1995) which
demonstrated the associat ion between the EMG median frequency
and recrui tment of the muscle f ibres. This associat ion was based on
the fact that the EMG median frequency of a muscle f ibre pr imari ly
ref lects i ts conduct ion veloci ty. Since fast twi tch muscle f ibres have
faster conduct ion veloci t ies, muscles with a high proport ion of fast
twi tch f ibres tend to have a higher EMG median frequency (Gerdle et
a l . , 1988, Kupa et a l . , 1995). Furthermore, the EMG median
frequency of the quadr iceps and the hamstr ings dur ing a l inear ly
increasing contract ion was invest igated in 18 adul ts subjects
(Bernardi et a l . , 1997) Resul ts conf i rmed that EMG median
frequency increases with increasing contract ion intensi ty as fast
twi tch motor uni ts are progressively recrui ted.
36
In the ear l ier s tudy of EMG changes fol lowing ACL reconstruct ion,
McNair and Wood (1993) analysed the frequency shi f t of the EMG
signal using the EMG median frequency. A t ime ser ies analysis
package TSA (NAG, England) was used to analyse the EMG data
and the power spectra were der ived using an FFT algor i thm and
smoothed using a Daniel l window. The median frequency of the
EMG power spectrum was obtained by summing the power est imates
at each incremental f requency to obtain the cumulat ive power. The
frequency at which hal f the total cumulat ive power occurred was
def ined as the median f requency. As ment ioned previously,
appl icat ion of the FFT algor i thm to surface EMG when determining
EMG median frequency has been ci ted as an example of a source of
potent ia l exper imental error (Kupa et al . , 1995). FFT should be
computed within the range of mot ion at which peak muscle strength
occurs, otherwise, exper imental error would ar ise. Further more, the
cont inuous changes in muscle f ibre length and cross-sect ional area
of a muscle f ibre dur ing dynamic contract ions pose a major technical
problem in analyzing surface EMG (McHugh et al . , 2002b). The
protocol adopted in the study conducted by McNair and Wood (1993)
was designed to obtain the power spectral analysis of the EMG
median f requency from a maximal muscle contract ion appl ied
through the range from 90° of knee f lexion to fu l l knee extension
(anatomical neutral ) , at a jo int veloci ty of 180° per second. The fu l l
90° mot ion would therefore take 500 mi l l iseconds (90/180=0.5
second) to complete. Dur ing th is 500 mi l l isecond of dynamic muscle
contract ion, muscle length cont inued to change, resul t ing in
cont inuous changes to the muscle f ibre diameter and a change in
EMG median frequency. Addi t ional ly, motor uni t f i r ing rate changes
37
with a change in the muscle length (Christova et a l . , 1998).
Consequent ly, the FFT algor i thm used to analyze the EMG signals o f
the whole 500 mi l l iseconds of knee muscle act ion may produce some
inaccurate resul ts. Nevertheless, McHugh and col leagues (2002a)
concluded that i t is more di f f icul t to ensure stabi l i ty of the EMG
signals dur ing dynamic than dur ing isometr ic contract ions. This may
explain why isometr ic contract ion may be a more favorable mode of
muscle contract ion when evaluat ing the EMG median frequency in
the predict ion of muscle f ibre composi t ion. This statement requires
further sc ient i f ic ver i f icat ion.
The relat ionship between EMG median frequency and fat igue have
been extensively studied (Big land-Ritchie et a l . , 1981, Potvin, 1997,
Linnamo et al . , 2000, Gerdle et a l . , 2000, Ng et al . , 2002, van Lent
et a l . , 1994, McHugh et al . , 2000, Lowery et a l . , 2002, Linssen et
al . , 1991b, Cornwal l et a l . , 1994, Masuda et al . , 1999, Warren et al . ,
2000, Koumantakis et a l . , 2001a). Dur ing sustained fat iguing
contract ions, the EMG median frequency is observed to shi f t towards
the lower f requency, which was at t r ibuted to a proport ional decrease
in muscle f ibre conduct ion veloci ty (Merlet t i et a l . , 1990, Lowery et
a l . , 2002, Masuda et al . , 1999, Taylor et a l . , 1997b). The decrease
in conduct ion veloci ty is due to an accumulat ion of metabol ic
byproducts such as lact ic acid, which reduces intracel lu lar pH and
decreases the exci tabi l i ty of the muscle f ibre membrane. The EMG
median f requency drop wi l l recover when the ef fects of the
accumulated byproducts are washed out by the blood-f low (Zwarts et
a l . , 1987, Masuda et al 1999). The recovery rate of the EMG median
frequency fol lowing fat igue was studied in a group of 20 males
38
(Cornwal l et a l . , 1994). The r ight quadr iceps of these subjects were
exercised using the Cybex I I+ isokinet ic dynamometer unt i l they
could not maintain 50% of the previously measured maximum
voluntary contract ion level . EMG median frequency was recorded
from the vastus lateral is using surface electrodes, before exercise
and at 10, 20, 40, 60 120 and 240 minutes af ter exercise. Resul ts
showed that recovery of the EMG median f requency of a muscle
occurs in less then 10 minutes.
2.1.2 Methods of measurement of muscle f ibre type
2.1.2.1 The biopsy technique
The muscle biopsy technique is recognised as an important, i f
not essent ia l , technique in the study of human skeletal muscle
(Evans et al . , 1982), and has been widely used for
histochemical as wel l as biochemical character isat ion of
di f ferent muscle f ibre types (Blomstrand and Ekblom 1982). I t
is of ten considered the ‘gold standard’ for the assessment of
muscle f ibre type and has been used with normal subjects
(Cost i l l e t a l . , 1976, Schantz et a l . , 1983, Grimby et al . , 1982)
and subjects wi th pathological condi t ions such as congeni ta l
myopathy (Linssen et al . , 1991,. Edwards et al . , 1980), spinal
cord in jury (Burnham et al 1997), neuromuscular disorders
( Imoto and Nonaka, 2000), and atrophic changes subsequent to
ACL in jury (Nakamura et a l . , 1986, Baugher et a l . , 1984,
Gerger et a l . , 1985). Commonly used biopsy techniques
provide var iat ions in the procedure for taking and analysing the
39
muscle sample and the accuracy of resul ts in ident i fy ing
muscle f ibre type have establ ished th is technique as super ior
to other techniques. Accordingly, the technique has been used
to val idate other procedures such as the measurement of
cross-sect ional area (Reniers et a l . , 1970, Schantz et a l . ,
1983, Hel l iwel l et a l . , 1998, Krotk iewski et a l . , 1998),
conduct ion rate (Gerdle et a l . ,1991) and the median f requency
(Nakamura et a l . , 1986) of the muscle. Despi te i ts super ior i ty,
weaknesses have been ident i f ied. Kupa and co-workers (1995)
indicated that when used for histochemical analysis, the biopsy
represents only a port ion of the f ibres act ivated dur ing a
contract ion, and is not representat ive of the whole muscle. I t
has also been shown that consistent and proper select ion of
the biopsy si te are key factors to the success of the technique.
(Berman et a l . , 1984). Reproducib i l i ty of resul ts is also
problemat ic because of the di f f icul ty and impract ical i ty in
taking a dupl icate sample f rom the previous locat ion.
Addi t ional ly the technique can only be performed by trained
and exper ienced people wi th appropr iate col lect ion and storage
faci l i t ies. These factors coupled with the invasive nature of the
technique l imi t i ts appl icat ion as a rout ine measurement tool in
the ident i f icat ion of muscle f ibre type. These l imi tat ions have
lead researchers to seek al ternat ive non- invasive methods to
determine muscle f ibre type (McNair and Wood, 1993, Kupa et
al . , 1995, McHugh et al . , 2000).
40
2.1.2.2 The mechanomyography (MMG)
More recent ly the use of mechanomyography in monitor ing
muscle fat igue has been ref ined and has gained popular i ty
(Drake et a l . , 2003, Bajaj et a l . , 2002, Heier and Het land,
1999, Madeleine et al . , 2002). In a study of the ef f icacy of
techniques used to monitor muscular fat igue (Tarata 2003), the
surface EMG and mechanomyography (MMG) were compared.
Muscular fat igue was measured using the parameters of RMS
of the EMG and the median frequency (MF) of the muscle.
Recordings were taken from the same locat ion in the biceps
brachi i and the brachioradial is, of 18 heal thy subjects. Resul ts
showed that for both EMG and MMG, the RMS increased with
advancing fat igue and the MF progressively decreased from the
onset of muscle contract ion. I t was concluded that MMG can
also be used as an indicator of the degree of muscle act ivat ion
and for monitor ing muscle fat igue when the appl icat ion of
surface EMG is not feasible. In another s tudy (Bajaj et a l . ,
2002), MMG and surface EMG resul ts of 13 heal thy subjects
were compared to assess thei r re lat ive values under the
inf luence of post exercise muscle soreness of the f i rst dorsal
interosseus of the hand. In th is study the ampl i tude of the
RMS was used as the measurement parameter for both EMG
and MMG. The RMS ampl i tude of EMG and MMG were
recorded dur ing single concentr ic , isometr ic , and eccentr ic
contract ions at 0%, 25%, 50%, 75% and 100% of MVC. Resul ts
indicated that MMG RMS ampl i tude increased as a funct ion of
both t ime and the percentage of muscle contract ion (%MVC)
41
(p<0.001) whi le the EMG RMS ampl i tude increased as a
funct ion of MVC (p<0.001) and not wi th t ime (p=0.74). The
authors of the study concluded that the MMG and EMG signals
ref lected di f ferent muscle propert ies, and that in contrast to
EMG, the MMG appeared to provide useful informat ion in
relat ion to post-exercise muscle damage. The ef f icacy of the 2
techniques was also compared in a study of the s igni f icance of
low force cont inuous or in termit tent stat ic contract ions and
biofeedback on the development of muscle fat igue (Madeleine
et a l , 2002). The parameters of the RMS and the mean power
f requency (MPF) were used for both EMG and MMG
procedures. These factors were recorded for 10 minutes
dur ing a cont inuous elbow f lexion contract ion at 10% and 30%
of the MVC and an intermit tent contract ion of 6-seconds
fol lowed by 4-second rest intervals. The resul ts showed a
general pattern for the RMS values of both MMG and EMG wi th
an increase with contract ion t ime. In contrast , the EMG MPF
values decreased with contract ion t ime. Also the increase in
the RMS value was general ly more pronounced for the MMG
compared with the EMG, whi le the decrease in MPF value was
more consistent for the EMG than the MMG signal . These
f indings suggest that both EMG and MMG signals could provide
complementary informat ion about local ised muscle fat igue at
low-level muscle contract ion (10% to 30%of MVC). I t was
suggested that MMG may be an al ternat ive to EMG in the
measurement of muscle fat igue, post exercise muscle soreness
and possibly the assessment of muscle integr i ty, part icu lar ly
when using the parameters of RMS and mean power f requency.
42
However further studies are required to provide greater insight
into the mechanisms re lated to these procedures and to test
the muscle propert ies that in f luence MMG (Bajaj et a l . , 2002).
Summary
EMG median frequency, muscle biopsy procedures and MMG have
been used to ident i fy muscle f ibre types. Al though di rect
measurement through muscle biopsy is considered the most
accurate technique, i ts invasive nature l imi ts i ts rout ine use.
Al though the MMG technique shows considerable promise, more
research is required to determine i ts val id i ty under di f ferent
condi t ions. Consequent ly, inference of muscle f ibre f rom EMG
median frequency appears the more appropr iate measure for rout ine
examinat ion across signi f icant numbers of subjects.
2.1.3 Isometric contraction duration
Conduct ion veloci ty and the EMG median frequency can be used to
study the pattern of recrui tment of muscle f ibres dur ing isometr ic
contract ion performed at d i f ferent levels of force. EMG median
frequency changes fol lowing muscle fat igue (Mannion et a l . , 1998,
Roy et al . , 1989) as wel l as dur ing high levels of force appl icat ion
(Roy et al . , 1995, Roy et al . , 1989, Nargol et a l . , 1999). Select ion of
the durat ion of isometr ic contract ion to ef fect the most rel iable EMG
median f requency should therefore be determined in relat ion to the
qual i ty of the force measures (adequate force level and stabi l i ty)
43
and the t ime to reach muscle fat igue (Lar iv iere at a l . , 2001).
Durat ion of contract ion should be long enough to maintain stabi l i ty
in muscle force and avoid muscle fat igue. This part ly explains why
the durat ion of an isometr ic contract ion used to determine EMG
median f requency has var ied in di f ferent exper iments and from
muscle to muscle. However, for research which has invest igated
muscle fat igue, isometr ic contract ion has been general ly maintained
for over 30 seconds, whereas in research which has at tempted to
rel iably determine EMG median f requency, contract ion durat ion was
3 to 7 seconds (Blazevich et a l . , 2002, Penn et a l . , 1999, Gogia and
Sabbahi, 1990, Montes Mol ina et a l . , 2000, Ebersole et a l . , 2002). I t
was indicated that (Lar iv iere et a l . , 2001), the durat ion of
contract ion should not al low the possib i l i ty of fat igue to occur, which
would af fect the rel iabi l i ty of the EMG median frequency. With
increased fat igue, the EMG power spectrum would at some stage,
begin to compress, causing the EMG median f requency to decrease.
To evaluate the ef fect of d i f ferent durat ions of isometr ic contract ion
on fat igue and EMG median f requency, 20 male subjects completed
a range of muscle contract ions of thei r back muscles (Lar iv iere et
a l . , 2001). Subjects were requested to perform two 8-second (2
seconds to reach the predetermined force level and 6 seconds to
sustain) isometr ic t runk extensions at 5 sub-maximal force levels.
Three segments of the signal were analyzed, and Hamming windows
(250 mi l l iseconds, 1024 points) were appl ied to the signal pr ior to
extract ing the corresponding EMG median frequencies f rom the
power spectrum. The f i rs t segment was windowed as soon as the
moment was stable as determined by visual observat ion. The
44
second and the thi rd t ime windows began at approximately the 3rd
and 4.8th second of the contract ion respect ively. The resul ts of th is
study showed that muscle fat igue did not occur dur ing the f i rst 5
seconds of isometr ic contract ion. As such i t was recommended that
the durat ion of isometr ic contract ion can be at least up to f ive
seconds. Concurrent ly, the placement of the window for an FFT
algor i thm should be located in the in i t ia l stage of contract ion (wi th in
the f i rst 3 seconds) to avoid the ef fect of fat igue and to help reduce
the var iabi l i ty in EMG median frequency (Lar iv iere et a l . , 2001).
Simi lar studies in th is area are l imi ted and have involved the t runk
muscles rather than the quadr iceps and the hamstr ings. I t is
possible that d i f ferent muscles may stabi l ize at d i f ferent t imes and
establ ish di f ferent thresholds for fat igue. More research is required
to object ively conf i rm the rel iabi l i ty of using a speci f ic durat ion of
isometr ic contract ions in producing rel iable EMG median frequency
resul ts .
2.1.4 Reliabil i ty of determining EMG median frequency
EMG median frequency has been widely used cl in ical ly. A bi latera l
shi f t in the EMG median frequency of a muscle may infer an atrophy
of a muscle f ibre (McNair and Wood, 1993, Kupa et al . , 1995,
McHugh et al . , 2002b, Roy et al . ,1989). Therefore ear ly detect ion of
the bi lateral asymmetry in EMG median frequency may assist in
restor ing or prevent ing muscle f ibre loss. In addi t ion, a drop in EMG
median f requency is an indicator of muscle fat igue (Dedering et a l . ,
2000, Ng et a l . , 1996, Lowery et a l . , 2002, Bigland-Ri tchie et a l . ,
1981) The onset and rate of fat igue development of muscles
45
ref lected by the change in EMG median frequency may be a usefu l
indicator of muscle status fol lowing in jury for example to the
shoulder and back and in the rehabi l i tat ion of in jury (Davis et a l . ,
1998). However before this measure can be used in these funct ions
i ts re l iabi l i ty must be assured.
Rel iabi l i ty refers to the consistency of a measurement tool (Deder ing
et a l . , 2000) or sometimes refers to the reproducibi l i ty of a
measurement (El fv ing et a l . , 1999). The test-and retest method has
been widely used for determining the re l iabi l i ty of measurements on
repeat tests (Dedering et a l . , 2000, Bl iodeau et a l . , 1994, Davis et
a l . , 1998, Sleivert and Wenger, 1994, Ng et al . , 1996, Nargol et a l . ,
1999, Biedermann et al . , 1990, El fv ing et a l . , 1999). The interval
between the in i t ia l and f inal tests di f fers f rom study to study, and
may vary f rom days to minutes. Repeat measurements may be taken
between days (day-to-day rel iabi l i ty) , between sessions wi th in a day
( inter-session rel iabi l i ty) , or between bouts wi th in a session ( intra-
session rel iabi l i ty) . However the re l iabi l i ty between consecut ive
contract ions wi thin a bout is not common.
In a previous study (Davis et a l . , 1998), the inter-session
(electrodes removed and reappl ied between tests) and int ra-session
(electrodes not removed between tests) re l iabi l i ty of the EMG
median frequency of the e lbow f lexors of 30 subjects was compared.
In the evaluat ion of intrasession rel iabi l i ty , subjects performed two
ident ical bouts of muscle contract ion wi th the EMG Median
frequency taken 30 minutes apart in one session without removing
the electrodes. Subjects were also required to perform two ident ica l
46
bouts of muscle contract ion in two separate sessions 1 to 3 weeks
apart . A s igni f icant ly higher rel iabi l i ty was found in the intrasession
rel iabi l i ty (98%) as compared to the intersession rel iabi l i ty (28%). A
possible explanat ion for such a resul t may be found in the var iance
associated with repeated at tachment of e lectrodes, part icular ly f ine
wire electrodes, together wi th the d i f ferent exper imental
environments dur ing the intersession evaluat ion. Previous
evaluat ion of the rel iabi l i ty of the EMG median frequency of vastus
medial is (Merlet t i et a l . , 1998), indicated that averaging out the
resul ts of repeated tr ia ls of muscle contract ions wi thin the same
session would improve rel iabi l i ty . However, large var iance was
found in the test and re-test procedure separated by several days.
I t was suggested that readjustment of the electrode locat ions and
st imulat ion intensi ty before each test session may be necessary to
minimize the var iances.
Ear l ier research has provided inconsistent resul ts wi th respect to the
relat ionship between EMG median frequency and the percentage of
maximum voluntary contract ion (MVC) of the muscle. In one study
(Roy et al . , 1995), EMG median f requency was not in f luenced by the
percentage of maximum voluntary contract ion of back muscles. In
another study, eccentr ic isometr ic contract ions of d i f ferent intensi ty
af fected the conduct iv i ty of the muscle f ibre in the l imbs and
produced di f ferent EMG median frequency responses (McHugh et
a l . , 2002b). In the lat ter study, the EMG median frequency
increased by 5 Hz when the intensi ty of muscle contract ion was
increased from 25% to 50 %. In addi t ion, when comparing di f ferent
percentages of submaximal voluntary isometr ic contract ion in
47
predict ing the EMG median f requency slope for the assessment o f
endurance in back muscles, the ef for t of 60% of MVIC was
previously reported to be more rel iable (Koumantakis et a l . , 2001a).
Pincivero et a l . , (2001) tested the inf luence of 9 d i f ferent in tensi t ies
of MVIC (10% across to 90% of MVIC at 10% increments) on the
EMG median frequency of the vastus lateral is , vastus medial is and
the rectus femoris of 15 heal thy males. No correlat ions were found
between the contract ion intensi t ies and the EMG median frequency
values for any of the muscles. For vastus media l is, the highest and
lowest EMG median frequency values were obtained at 50 and 90%
of MVIC respect ively. Values for rectus femoris , were highest at 60%
and lowest at 80% and for vastus lateral is, the higher and lower
values were recorded at 70 and 20% of MVIC respect ively.
Interest ingly, in the transformat ion process used to determine the
EMG median frequency, the var iabi l i ty across the 11 over lapping
windows was not related to the intensi ty of the MVIC. The highest
and the lowest var iabi l i ty occurred at 70% and 20% of the MVIC for
the vastus media l is and at 90% and 40% and 80% and 50% for the
medial hamstr ings and vastus lateral is respect ively. These resul ts
suggest that EMG median frequency is inf luenced by the intensi ty of
isometr ic contract ion and when comparisons in re lat ion to EMG
median frequency are made across studies, the same percentage of
intensi ty of force should be performed among subjects. Important ly,
i r respect ive of the intensi ty of the intensi ty of muscle ef fort used in
the above studies, no between-l imb di f ferences in EMG median
frequency were ident i f ied (Pincivero et a l . , 2001, Koumantakis et a l . ,
2001a, Roy et a l . , 1995, McHugh et al . , 2002b). This suggested that
48
the isometr ic contract ion at d i f ferent intensi t ies did not af fect the
bi lateral symmetry of the EMG median frequency slope provided that
an equal intensi ty of muscle contract ions was performed bi lateral ly
and concurrent ly wi thout causing fat igue. Equal intensi ty of muscle
contract ions is most accurate ly and easi ly obtained at their maximal
ef for ts. The r isk of causing fat igue is not an issue, provided that the
durat ion of contract ion can be careful ly moni tored. The resul ts of
these studies suggest that maximum voluntary isometr ic contract ion
(MVIC) can be used to rel iably determine the EMG median
frequency.
The rel iabi l i ty of the EMG median frequency may also be inf luenced
by the durat ion of muscular contract ion and the method of
processing the EMG signal (Kupa et a l . , 1995). Research has shown
that when determining the median f requency, the durat ion of muscle
contract ion should be of a length that wi l l a l low t ime for recrui tment
of a l l muscle f ibres wi thout producing fat igue (McHugh et al . , 2000,
Kupa et al . , 1995). When processing EMG median f requency,
rel iabi l i ty may be af fected by the method of Four ier t ransformat ion
(McHugh et al . , 2002b). The precis ion of the FFT resul ts is related
to the durat ion of the EMG data sample within a given window dur ing
the FFT processing (Kar lsson et al . , 2000). The width of the FFT
window is expressed in terms of t ime uni ts (mi l l iseconds). I f the
window width is too smal l (e.g. <250 mi l l iseconds), the sampl ing
durat ion of EMG signals for processing the data wi l l be smal l and
consequent ly the resul ts of the FFT wi l l not be repeatable. This is
due to the sampl ing s ize of the EMG signal for processing being too
smal l . In contrast , i f the window width is too large (e.g. >3000
49
mil l iseconds), the resul ts of the FFT wi l l be af fected by the var iat ion
in muscle act iv i ty dur ing the longer contract ion. McHugh and
col leagues (2000) suggested that i t was more di f f icul t to ensure
stabi l i ty of the EMG median frequency of a muscle dur ing dynamic
than dur ing isometr ic contract ion. This suggest ion is yet to be
scient i f ica l ly conf i rmed by further research.
50
2.2 The anterior cruciate l igament
EMG median frequency has been used to predict changes in muscle
f ibre composi t ion of the quadriceps muscle which undergoes atrophy
fo l lowing anter ior cruciate l igament (ACL) in jury. As th is is a
common injury to the knee, knowledge of the status of the muscles
surrounding the knee is important in post in jury rehabi l i tat ion.
2.2.1 Muscular adaptation fol lowing ACL reconstruction
The anter ior cruciate l igament ar ises f rom the anter ior in ter-condylar
area of the t ib ia and passes upwards, backwards and lateral ly,
before insert ing onto the poster ior part of the medial surface of the
lateral condyle of the femur (Snel l , 1973). The ACL contr ibutes to
the antero-poster ior stabi l i ty of the knee and loss of funct ion causes
abnormal anter ior d isplacement wi th respect to the t ib ia. I t is wel l
known that atrophy occurs in the musculature surrounding the knee
fol lowing ACL in jury due to the decrease in knee act iv i ty as a
funct ion of pain and instabi l i ty. Pat ients wi th an ACL def ic ient knee
have a signi f icant ly lower than normal net quadr iceps moment dur ing
walking, because quadr iceps contract ion produces an anter ior ly
directed force on the t ib ia causing instabi l i ty (Andr icchi , 1993,
Berchuck et a l . , 1990). Adaptat ion of the muscle occurs as a
funct ion of the resul tant instabi l i ty of the knee jo int , wi th loss of
muscle f ibre which is f ibre type speci f ic (Edstrom, 1970, Baugher et
a l . , 1984, Nakamura et a l . , 1986, Gerber et a l . , 1985, McNair and
Wood, 1993). Research f indings di f fer in relat ion to the type of
muscle f ibre that atrophies. Some researchers (Edstrom, 1970,
51
Nakamura et al . , 1986) have reported atrophy of type I f ibres
fo l lowing ACL in jury, whereas others have found a reduct ion in the
cross-sect ional area of type I I f ibres (Baugher et a l . , 1984, McNair
and Wood, 1993). Others (Gerber et a l . , 1985) have shown atrophy
of both type I and type I I muscle f ibres in equal proport ions.
In a his tochemical study (Edstrom, 1970), b iopsies were taken f rom
the vastus medial is of 11 pat ients wi th ACL in jury. Of these
pat ients, 10 were chronic cases with a mean durat ion of symptoms
of 25.8 months, ranging from 6 months to 4 years. One subject was
an acute case. Three pat ients had isolated ACL injury and the
others had a var iety of in jur ies involving the meniscus and col lateral
l igament in jury, isolated meniscus in jury and chondromalacia
patel la. Resul ts showed that the red or type I f ibres of vastus
medial is in those with an ACL in jury l imb had a lower mean cross-
sect ional area when compared to that of the white or type I I f ibres.
This indicated that there was a select ive atrophy of type I f ibres,
because the red and white f ibres of normal quadr iceps should
approximately be equal in s ize (Edstrom and Nystrom, 1969).
In another study (Nakamura et a l . , 1986), the ef fect of d i f ferent knee
in jur ies on muscle atrophy was examined using the biopsy technique
to determine muscle f ibre relat ionships. The pat ients were div ided
into 4 sub-groups represent ing d i f ferent in jury categor ies: an
isolated ACL injury group; an ACL in jury and associated meniscus
in jury group; an isolated meniscus in jury group; and a col latera l
l igament in jury group. Biopsies were taken from the vastus lateral is
using the techniques descr ibed by Brooke and Engel (1969).
52
Analysis of the biopsies indicated that the populat ions of muscle
f ibres in the atrophied muscle di f fered among subject groups and
ref lected the di f ferent in jury condi t ions. In both the isolated ACL
and ACL + meniscus in jury groups select ive atrophy of the type I
f ibres was found which did not occur in the other two in jury
categor ies. The resul ts suggest adaptat ion of the knee muscles
fo l lowing ACL in jury may be di f ferent f rom other knee in jur ies.
The t ime dependent nature of muscular adaptat ion fol lowing ACL
injury was invest igated in a biopsy study of the vastus medial is
(Baugher et a l . , 1985). Muscle f ibre composi t ion was evaluated in
chronic ACL in jured male pat ients wi th knee instabi l i ty of longer than
12 months durat ion and compared with s imi lar informat ion f rom
pat ients wi th an acute in jury of only 4 to 11 days durat ion. Atrophy
of type I I f ibre was found only in the chronic ACL in jury group,
indicat ing that select ive atrophic changes in muscle f ibre
composi t ion had not occurred in the acute stage of ACL in jury but
was more apparent af ter several months fol lowing the in jury.
The f inding of select ive atrophy of type I I muscle f ibres was
supported in a study (McNair and Wood, 1993) which compared the
muscle f ibre composi t ion of the in jured and contralateral l imbs of 17
subjects wi th chronic ACL def ic iency. The mean age of the subjects
(8 males and 9 females) was 27 years and the t ime since their in i t ia l
in jury was an average of 20 months. The bi la teral strength in terms
of the peak torque generated by the quadr iceps muscles dur ing
isokinet ic muscle act ion was evaluated and used to assign subjects
into maximal and minimal def ic iency groups. In contrast to the
53
biopsy studies, th is invest igat ion used a f requency analysis of the
EMG signals dur ing contract ion to predict the type of muscle f ibre
atrophy. In that study, EMG signals were relayed to a data
acquis i t ion system operat ing at a sampl ing f requency of 1000 Hz.
The power spectra were der ived using a Fast Four ier t ransformat ion
and smoothed by a Daniel l window. A power spectral analysis of the
EMG obtained from the vastus lateral is muscle dur ing the maximum
effort of knee extension performed at 180° per second was
undertaken to examine the di f ferences in EMG median frequency
between l imbs. The resul ts showed that in the maximal def ic iency
group, the vastus lateral is muscles of the ACL def ic ient l imb had a
s igni f icant ly lower EMG median f requency than that of the
uninvolved l imb (p<0.05). From previous research which showed a
lower EMG median frequency associated with type I I atrophy, i t was
interpreted that at rophy of th is f ibre type had occurred in th is
component of the quadr iceps of the ACL def ic ient knees.
Atrophy of muscle f ibres in chronic ACL in jury pat ients has been
examined in a study which used both histochemical and
ul t rastructural analyses (Gerber et a l . , 1985). The durat ion of
symptoms ranged from 6 weeks to 10 years, wi th an average of 28
months and was shorter in women (17.3 months) than men (30.9
months). The resul ts showed a simi lar decrease in the size of both
type I and type I I f ibre muscle f ibres which lead the authors to
suggest that there was no scient i f ic rat ionale for select ive
rehabi l i tat ion of e i ther type I or type I I muscle f ibre in pat ients wi th
chronic ACL in jury.
54
The var iabi l i ty in the resul ts of these studies make comparisons
between studies di f f icul t and the development of any consensus with
respect to f ibre type involvement in ACL related atrophy somewhat
premature. The reason for the di f ferences in the f indings is
mul t i factor ia l and may ref lect di f ference in age and gender, t iming
post in jury, nature and extent of the in jury, muscle select ion and
methodological d i f ferences.
2.2.2 The rehabil i tation of ACL injury or reconstruction
ACL in jury was always regarded as " the beginning of the end for the
knee" (Giove et a l . , 1983, Torg et a l . , 1976). In spi te of the high
incidence of ACL in jury, controversy remains as to the most
appropr iate t reatment and management of the in jury (Giove et al . ,
1983, Woo et a l . , 1997). The long-term success of an ACL
reconstruct ion depends on several factors, including the
rehabi l i ta t ion protocol prescr ibed af ter surgery (Fleming et a l . ,
1998). Some authors have even considered the post-operat ive
rehabi l i tat ion program to be as important as the surgery i tsel f
(Paulos et a l . , 1981, Beard and Dodd, 1998). Despi te the
importance placed on rehabi l i ta t ion and the broad var iety of
rehabi l i tat ion programs avai lable, the precise def in i t ion of the
opt imal in tensi ty, f requency and durat ion for the program remains
elusive (Beynnon et a l . , 1995) and remains a controversial issue
(Timm, 1997, Fleming et a l . , 1998, Giove et al . , 1983, Li et a l . ,
1996, Woo et al . , 1997). Discussion in th is area include: the nature
of the adaptat ion and the t iming of muscle atrophy subsequent to
ACL in jury; the relat ive balance between the knee extensors and
55
knee f lexors (e.g. the quadr iceps or hamstr ings) to achieve opt imal
stabi l i ty ; and the ef f icacy of d i f ferent exercise devices and exercise
types used in the var ious rehabi l i tat ion programs.
2.2.3 The importance of the hamstrings and quadriceps ratio in
the rehabil i tation of ACL injury and reconstruction
Loss of ACL funct ion has been shown to lead to increased
mechanical instabi l i ty and subsequent al terat ion of normal gai t
pat terns (But ler et a l . , 1980, Grood et al . , 1984, Wexler et a l . ,
1998). A reduct ion in quadr iceps contract ion force when the knee is
near fu l l extension helps to diminish anter ior t ranslat ion of the
proximal t ib ia (Wexler et a l . , 1998). Pat ients suf fer ing from ACL
def ic iency seem to compensate for th is mechanical instabi l i ty by
avoiding contract ion of the quadr iceps dur ing the mid-port ion of the
stance and through non-support to foot str ike in walk ing (Andr iacchi ,
1993, Noyes et a l . , 1990, Berchuck et a l . , 1990). This funct ional
adaptat ion is referred to as the “quadr iceps avoidance” gai t pat tern
which is learned in an ef fort to minimise the anter ior t ib ia l
t ranslat ion caused by the quadr iceps contract ion (Noyes et a l . ,
1990, Berchuck et a l . , 1990, Wexler et a l . , 1998, Hurwi tz et a l . ,
1997, Devi ta et a l . , 1997).
I t is general ly accepted that quadr iceps training fol lowing ACL in jury
wi l l promote anter ior t ranslat ion of the t ib ia and create excessive
strain on the ACL. As a resul t , the importance of quadr iceps
training af ter ACL in jur ies was not emphasized (Giove et al . , 1983,
Noyes et al . , 1984). In addi t ion, ACL reconstruct ion was rarely
56
performed dur ing the acute stage of in jury (Shelbourne and Foulk,
1995), and therefore, the per iod of “quadr iceps avoidance” af ter the
ACL in jury is usual ly qui te long. This may resul t in some
irreversible knee jo int st i f fness or loss of mot ion and contracture of
the quadriceps (Fu et al . , 1992). I t may also explain why atrophy or
weakness of the quadr iceps of ten occurs short ly af ter the ACL knee
reconstruct ion. However, i t is important to real ise that the weakness
or at rophy may have been present pr ior to the reconstruct ion due
mainly to an adaptat ion in gai t fo l lowing the rupture (Fu et al . , 1992,
Timm 1997, I r rgang and Harner, 1997, Snyder-Mackler et a l . , 1995,
Jennings and Seedhom, 1994, Lutz et a l . , 1993).
I t has been reported that weakness of the quadr iceps subsequent to
ACL in jury or reconstruct ion may cause patel lo- femoral pain in
addi t ion to a loss of knee extension (Harner et a l . , 1992, Fu et a l . ,
1992). In 1995, Snyder-Mackler and col leagues suggested that
weakness of the quadr iceps af ter reconstruct ion of the ACL may be
at t r ibuted to patel lo- femoral pain, deformity of the jo int , or lesions
within the art icular cart i lage. Consequent ly, researchers started to
real ise that the quadr iceps st rength of the ACL def ic ient knee had to
be mainta ined but wi thout increasing the anter ior stress placed on
the reconstructed l igament. This st imulated greater interest in
def in ing the most appropr iate rehabi l i tat ion procedure for t ra ining
the quadr iceps muscle (De Carlo et a l . , 1997).
The inherent problem of quadr iceps tra in ing for developing anter ior
t ranslat ion of the t ib ia and excessive stress on the heal ing ACL has
also encouraged increased interest in the role of the hamstr ings
57
musculature in ACL rehabi l i tat ion. Strengthening the hamstr ings has
not been shown to produce the deleter ious shear forces associated
with quadr iceps contract ion (Henning et a l . , 1985, Kaufman et al . ,
1991a, Kaufman et al . , 1991b, Lutz et a l . , 1993). In addi t ion, co-
contract ion of the hamstr ings and quadr iceps dur ing knee extension
may also reduce the anter ior t ranslat ion of the t ib ia and increase the
stabi l i ty of the ACL def ic ient knee (Li et a l . , 1996, Noyes et a l . ,
1983, Giove et al . , 1983). In turn, strengthening the hamstr ings
could help to protect the heal ing graf t dur ing funct ional act iv i t ies
(Lutz et a l . , 1993) and could in part serve to replace the funct ion of
the ACL.
Giove and col leagues (1983) emphasised the strengthening of
hamstr ings in the rehabi l i tat ion of ACL in jur ies in athletes. They
found that higher levels of sports part ic ipat ion were achieved by
those ACL def ic ient pat ients whose hamstr ings strength was equal
to, or greater than, the st rength of thei r quadr iceps, that is to
elevate the H:Q rat io f rom a normal value of 60% to 100%. Thei r
f indings and later research (Tibone et a l . , 1986) suggested that
increasing the relat ive st rength of the hamstr ings with respect to the
H:Q rat io could help compensate for the loss of the torn or
reconstructed l igament.
With increasing recogni t ion of the potent ia l dangers of quadr iceps
exercise in ACL rehabi l i tat ion, such as increasing stress of the ACL,
c l in ical pract ise now emphasises strengthening the hamstr ings and
select ing quadr iceps strengthening exercise which do not produce
the negat ive ef fects on the heal ing of the ACL. Examples were in-
58
vivo exper iments using st rain gauges at tached to the l igament dur ing
surgery have been used to determine the relat ive mechanical loads
on the l igament as a funct ion of d i f ferent exercise regimes. The
resul ts have shown that the quadr iceps can be exercised
isometr ical ly at knee f lexion angles between 60° and 90° wi thout
causing undue stress to the ACL (Arms et a l . , 1984, Renstrom at al . ,
1986). These f indings did not account for al l factors or
compl icat ions associated with quadr iceps involvement, in part icular
the patel lo- femoral pain syndrome which is commonly encountered
af ter ACL reconstruct ion (Clancy et a l . , 1982). This condi t ion is
exacerbated dur ing resist ive quadr iceps exercises performed at
angles of knee f lexion greater than 30°. Consequent ly, no complete
protocol for ACL rehabi l i tat ion has been sat isfactor i ly ident i f ied and
further research is necessary.
A cadaver ic exper iment conf i rmed that anter ior displacement of the
t ib ia and stretching of the secondary restraints of the ACL def ic ient
knee occurred in the last 30° of knee extension (Grood et a l . , 1984).
This leads to the suggest ion that exercis ing in the upr ight posture to
al low the “ force of weight bear ing” would counter the problem of
excessive anter ior t ib ia l shear or t ranslat ion. This hypothesis was
supported by Henning and col leagues (1985) who found that
isometr ic knee extension between 0° and 22° produced more st ress
on the ACL than weight bear ing exercises such as cyc l ing using a
stat ionary bike, walk ing on level ground, jumping rope, or performing
a hal f -squat wi th one leg. These resul ts indicated that weight-
bear ing or c losed kinet ic chain exercises can be used to s trengthen
the quadr iceps wi thout jeopardis ing the stabi l i ty of the reconstructed
59
ACL. Consequent ly, c losed chain exercises have been prescr ibed in
a major i ty of the ACL rehabi l i tat ion programs with the object ive of
reducing the anter ior t ranslat ion of the t ib ia dur ing the last 0° to 30°
of quadr iceps exerc ise (Wi lk and Andrew 1992, Blair and Wil ls 1991,
De Carlo et a l . , 1992, Shelbourne and Nitz, 1992, Shelbourne et al . ,
1992, Mangine and Noyes 1992, Hal l ing et a l . , 1993, Li et a l . , 1996,
Clasby and Young, 1997, Jur is et a l . , 1997, Arnold et a l . , 1997).
In summary, knee movements which do not place addi t ional strain on
the ACL, or do not increase the anter ior t ranslat ion of the t ib ia, such
as hamstr ings exercises, can st i l l be performed safely and
ef fect ively even using open kinet ic chain exercises with appropr iate
modif icat ions (Br indle et a l . , 2002). Addi t ional ly, the concept of
increasing the hamstr ings st rength to make the H:Q rat io equal to
one is also important and should be g iven greater emphasis in the
ACL rehabi l i tat ion program (Giove et a l . , 1983, Li et a l . , 1996).
2.2.4 Functional abil i ty of the ACL reconstructed knee
The high incidence of knee in jur ies has st imulated the development
of several instruments designed to evaluate the funct ional status of
the knee. A commonly used instrument is the Cincinnat i Knee Rat ing
System (Noyes et a l . , 1984) which is wel l accepted for use in a
c l in ical set t ing. This system is developed around a number of
c l in ical or funct ional symptoms which are given a score depending on
the sever i ty of a part icular symptom. Pain, swel l ing and giv ing way
are al lot ted a maximum score of 50 points as are the abi l i ty to
perform general act iv i t ies such as walk ing, running, c l imbing stairs ,
60
jumping and twist ing which are al lot ted a s imi lar score. The points
are al located against establ ished cr i ter ia relat ive to each test i tem.
A normal knee would receive a total score of 100 points represent ing
a combinat ion of both c l in ical and funct ional rat ings. The rel iabi l i ty
and val id i ty of th is system have been examined. Rel iabi l i ty was
determined from the responses of 100 subjects who completed the
system twice with an average of a week apart . Resul ts demonstrated
high test and re-test re l iabi l i ty wi th inter-c lass correlat ion
coeff ic ients greater than 0.70 (Barber-West in et a l . , 1999). I t was
concluded that the Cincinnat i Knee Rat ing System has acceptable
rel iabi l i ty , val id i ty and responsiveness for use in the outcome of the
studies af ter ACL reconstruct ion (Barber-West in et a l . , 1999).
Among other commonly used instruments of evaluat ion of the
funct ional outcomes of the knee, i t is one of the few which is
speci f ical ly designed for the funct ional evaluat ion of an ACL in jury or
ACL reconstruct ion.
61
2.3 The role of isokinetic technology in ACL rehabilitation
There is evidence to suggest that isokinet ic exercise is the super ior
mode of resistance training for restorat ion of muscle s ize and
strength (Thist le et a l . , 1967, Pipes and Wilmore, 1975). This
evidence is based on a large number of exercise intervent ions which
have been implemented in a range of rehabi l i tat ion sett ings. An
ear ly comparat ive study of isokinet ic and isotonic exercise using the
Cybex I I and Naut i lus equipment indicated that 6 weeks of fast
isokinet ic t ra ining was more ef fect ive than that of the isotonic
exercise in increasing the st rength of male adolescents (Smith and
Mel ton, 1981). Since then, the advantages of isokinet ic
dynamometers and the methods of advancing this technology have
been widely invest igated (Adeyanju et a l . , 1983, Garnica, 1986,
Kannus, 1988, Jones and Rutherford, 1987, Timm, 1997, Kramer,
1990, El lenbecker et a l . , 1997, Ewing Jr et a l . , 1990, Li et a l . , 1996,
Parcel l e t a l . , 2002, Tesch et al . , 1990, Nisel l et a l . , 1999, Sargeant
et a l . , 1994, Haut ier et a l . , 1996).
2.3.1 Selective muscle f ibre training in isokinetic movements
The unique capaci ty of isok inet ic dynamometers to provide a range
of contract ion speeds is considered important in target ing speci f ic
types of muscle f ibres dur ing rehabi l i tat ion protocols (Coyle et a l . ,
1979, Grimby, 1985, Sherman, 1982, Dvi r , 1990). Speeds may be
selected up to 600° per second wi th speed below 180° per second
considered in the s low range. Exercise in th is range is bel ieved to
62
target and strengthen slow twi tch f ibres whereas speeds above this
range select ively strengthen fast twi tch f ibres (Kannus, 1994).
However these concepts have not been scient i f ica l ly conf i rmed.
Indirect evidence of the adaptat ion of muscle f ibres to di f ferent
speeds of contract ion is provided by invest igat ion of ath letes in
di f ferent events. An ear ly and wel l accepted study of muscle f ibre
types in the vastus lateral is of spr inters, pentathletes and middle
and long distance runners (Gregor et a l . , 1979) indicated that the
relat ive cross-sect ional areas of muscle f ibres ref lects the athletes
events. Spr inters ( fast twi tch) and long distance runners (s low
twi tch) were represented at opposi te ends of the cont inuum.
Athletes special is ing in pentathlon and middle-distance running had
a muscle f ibre prof i le which fe l l between these extremes. In
addi t ion, the actual cross-sect ional area of the fast twi tch muscle
f ibres of d i f ferent types of ath letes var ied posi t ively and l inear ly wi th
the speed of l imb movement whi le s low twi tch muscle f ibres did not
correlate. The rat io of tota l cross-sect ional areas of s low twi tch
(ST) f ibres and fast twi tch (FT) f ibres (area ST/FT) was posi t ively
related to the speed of the l imb movements. The authors concluded
that there was a direct re lat ionship between the dis tr ibut ion of
speci f ic muscle f ibre types within a muscle and the speed of l imb
movement in which those muscles were involved.
Despi te these f indings, there were several l imi tat ions in the design
of the study which diminished their s igni f icance. These included the
cross-sect ional nature of the study, the lack of control over the
speed of muscle t raining, non-standardizat ion of the indiv idual
63
muscular adaptat ion per iod (durat ion) and the smal l sample s ize of
subjects in each subgroup (n=4 to 9).
An ear ly and f requent ly quoted study (Thorstensson et al . , 1976)
used 8 male subjects to invest igate the ef fects of an 8-week per iod
(24 sessions) of progressive strength t raining on the EMG act iv i ty of
the knee extensor muscles and muscle f ibre composi t ion.
Progressive muscular t ra in ing ( isotonic) included pr imari ly squats,
vert ical jumps and standard board jumps with maximum efforts . A
Bergstrom (1962) needle biopsy technique (Gol ln ick et a l . , 1972)
was used to determine the muscle f ibre composi t ion (d istr ibut ion of
fast twi tch and fast twi tch f ibres cross sect ional areas) of the vastus
lateral is muscle.
No signi f icant changes were found in the percentage of fast twi tch
muscle f ibres in vastus lateral is fo l lowing the training program.
However, a s igni f icant increase (14.2%) was found in the cross-
sect ional area rat ios of the fast twi tch and slow twi tch (FT / ST)
f ibres of the vastus lateral is. The authors concluded that the
increase in fast twi tch to s low twi tch f ibre rat io was a resul t of a
speci f ic ef fect of the tension (resistant) t ra in ing st imulus on fast
twi tch motor f ibre uni ts. Al though this was a longi tudinal study and
the amount and the durat ion of muscular t ra ining over a per iod of
t ime was standardized, the t raining resistance given to the muscle
motor uni ts was not standardized in relat ion to speed of contract ion.
The three tension (resistant) t ra in ing exercises (squats, vert ical
jumps and standard board jumps) used in th is exper iment were a l l
isotonic. The speeds of the muscle contract ions when doing these
64
exercises were not uni formly control led and involved s igni f icant
var iabi l i ty both between indiv iduals and across t raining sessions.
In summary, these studies indicate the response of speci f ic muscle
f ibre types to di f ferent exercise regimes and the resul ts provide a
basis for fur ther invest igat ion of the relat ionship between training
programs and the target ing of speci f ic muscle f ibre types.
2.3.2 The application of isokinetic technology to control muscle
contraction velocity during ACL rehabil i tation
In the rehabi l i tat ion of the knee fo l lowing ACL in jury or
reconstruct ion, considerable emphasis is placed on the ear ly
restorat ion of fu l l symmetr ical knee extension and the ear ly return to
funct ional or sport ing act iv i t ies (Fu et al . , 1992). Since atrophy of
muscle f ibres occurs short ly af ter ACL in jury as a funct ion of the
adaptat ion which occurs in relat ion to the changed loading
environment (Nakamura et al . , 1986, McNair and Wood, 1993,
Gerber et a l . , 1985), the t iming of commencement of the
rehabi l i tat ion program is a s igni f icant factor to a successful
outcome. A delayed start may induce muscle atrophy, whereas
start ing too ear ly may interfere with the heal ing process of the
l igament. A unique feature of isokinet ic technology is i ts abi l i ty to
provide an accommodat ing resistance, whereby dur ing isokinet ic
exercises torque decreases with increasing veloci ty (Kannus, 1994,
West ing et a l . , 1991). Since higher angular veloci t ies y ie ld less
resistance to the jo int , exercises at 240° to 300° per second are
recommended dur ing the in i t ia l stage of ACL rehabi l i ta t ion.
65
(Kannus, 1994). Hence, the funct ion of resistance accommodat ion
at var ious intensi t ies of loading has enabled isokinet ic exercise to
become an integral component of the strength-recovery process
af ter ACL in jury and reconstruct ion.
Al though important in the reduct ion of atrophy fo l lowing ACL injury,
the opt imal t iming for the commencement of safe isokinet ic exerc ise
remains controversial . Shelbourne and Nitz (1990), who devised the
concept of accelerated rehabi l i tat ion, recommended that isokinet ic
muscle evaluat ion should be started 5 weeks post-operat ively. Their
rehabi l i ta t ion program encouraged ear ly weight-bear ing, ear ly
mobi l isat ion of the knee and ear ly strengthening of the quadr iceps
(Shelbourne and Nitz, 1990, Shelbourne et a l . , 1992). Their
recommendat ion was supported by other invest igators (De Carlo et
a l . , 1992) wi th the qual i f icat ion that the range of knee terminal
extension not exceeds 20°. I t has been suggested (Markey, 1991)
that the use of isok inet ic exercise is only indicated when the muscle
strength of the ACL reconstructed knee is approximately 70% that of
the contra lateral l imb. This may occur as late as 6 months af ter the
operat ion. Al though support ing isokinet ic evaluat ion at week 5, Fu
and col leagues (1992) suggested that isokinet ic t ra in ing should not
be started unt i l 10 weeks post ACL reconstruct ion. Other
researchers (Blair and Wi l ls , 1991) supported a more aggressive
approach and recommended start ing isokinet ic t ra in ing at week 3
whi le other researchers have suggested t imes ranging f rom 6 to 7
weeks (Wi lk and Andrew, 1992, Mangine and Noyes, 1992) to 24
weeks (Frndak and Berasi , 1991) post-operat ively. Some
researchers do not recommend isokinet ic t ra in ing exercise in the
66
f i rst 3 months of the rehabi l i tat ion program and suggested that such
training should only be introduced in the second phase of
rehabi l i tat ion. This normal ly starts af ter 12 weeks post surgery
(Whit t ington and Carlson 1991), or even more conservat ively, in the
third phase of a 6-month post-operat ive per iod (Tegner, 1990).
Hence, there is no common consensus on the recommended t ime for
the commencement of isokinet ic exerc ise subsequent to ACL in jury
or ACL reconstruct ion.
Isokinet ic technology related l i terature (Kannus, 1994) suggests the
meri t of using exerc ise at d i f ferent speeds to act ivate a speci f ic type
of muscle f ibre in the rehabi l i tat ion of var ious condi t ions such as
ACL reconstruct ion (Li et a l . , 1996). However th is meri t requires a
scient i f ic conf i rmat ion wi th a good rel iabi l i ty . Thus an object ive of
the present invest igat ion is to determine a rel iable measurement of
EMG median f requency in response to di f ferent speeds of exercise.
67
2.4 Summary
I t is establ ished that ident i f icat ion of muscle f ibre composi t ion is
most di rect ly and accurately determined using biopsy technique.
However, i t is too invasive for rout ine assessment. Recent ly EMG
median frequency has been used as an al ternat ive to infer muscle
f ibre composi t ion. Unfortunately, there is a lack of scient i f ic
evidence in the l i terature to establ ish a rel iable protocol under
varying condi t ions of muscle contract ion to determine EMG median
frequency. This is essent ia l to val idate EMG median frequency as a
non- invasive predictor of muscle f ibre types against muscle biopsy
techniques. Such val idat ion wi l l a l low use of EMG median frequency
as a useful c l in ical measure in the ident i f icat ion of speci f ic muscle
f ibre def ic i ts fo l lowing ACL reconstruct ion or in jury and their return
to normal dur ing targeted rehabi l i tat ion programs.
68
Chapter Three
Evaluation of the reliability of the EMG median
frequency measured isometrically and isokinetically
3.1 Introduction
Median f requency is used to measure the t ime dependent changes in
EMG (Biedermann et al . , 1990, DeLuca, 1985, Masuda et al . , 2001).
Changes in the central tendency measures of the EMG power
spectrum are associated with the conduct ion veloci ty of the muscle
f ibres. In turn, th is conduct ion veloc i ty is related to muscle f ibre
s ize (Broman et a l . , 1985). In addi t ion, motor uni ts wi th large
muscle f ibres have been shown to be fast twi tch or type I I f ibres
(Henneman et al . , 1965). These relat ionships have provided the
basis for the calculat ion of the EMG spectral parameters such as the
median frequency which is related to the conduct ion veloci ty of a
muscle f ibre. Since type I I f ibres have faster conduct ion veloci t ies,
muscles composed pr imari ly of th is f ibre type have a greater
conduct ion veloci ty than those composed most ly of s low twi tch or
type I muscle f ibres. In contrast , muscles with a higher proport ion
of type I f ibres tend to have a lower median frequency (Gerdle et a l . ,
1988, Kupa et al . , 1995). Muscle biopsy has been the standard
procedure used in previous research for the ident i f icat ion of muscle
f ibre type from histochemical analysis, however the invasive nature
of the biopsy technique is inappropr iate for rout ine assessment. In
addi t ion s ingle muscle biopsy procedures provide a picture of
muscle f ibre populat ions at that s i te which is not necessar i ly
69
representat ive of the whole muscle (Kupa et a l . , 1995. Gerdle et a l . ,
1991, Wret l ing et a l . , 1987). In contrast , EMG techniques have been
used as a means of inferr ing muscle f ibre type non- invasively and
may provide informat ion which is more representat ive of the muscle
as a whole. This concept was val idated by the resul ts of a biopsy
study in rats which suggested that EMG median f requency and
conduct ion veloci ty parameters recorded dur ing a muscular
contract ion were related to muscle f ibre type composi t ion and
muscle f ibre cross-sect ional area (Kupa et al . , 1995). Since then
EMG median frequency has been general ly accepted as a non-
invasive tool to in fer muscle f ibre composi t ion (Bi lodeau et a l . , 2002,
McHugh et al . , 2002a, Toffola et a l . , 2001, Lar iv iere at a l . , 2001,
Pincivero et al . , 2001, Merlet t i et a l . , 1998, Gerdle et al . , 1997).
Evaluat ion of the use of EMG median frequency to infer f ibre type
was the focus of research concerned with the abi l i ty of EMG median
frequency to predict muscle f ibre type in atrophied muscle resul t ing
f rom ACL def ic iency (McNair & Wood, 1993). The resul ts showed a
direct correlat ion between the conduct ion veloci ty and the f ibre s ize
of the muscle and the authors concluded that the decrease in muscle
conduct ion veloci ty can be re lated to atrophy of type I I f ibres in ACL
def ic ient knees. Despi te th is conclusion, several quest ions have
remained with respect to the rel iabi l i ty of EMG median frequency.
Such informat ion is necessary i f EMG median frequency is to be
used as an indirect predictor of f ibre type. For example, no
evidence was provided of any normal values in EMG median
frequency of the uninvolved l imb as a reference to the ACL in jured
l imb. The associat ion between the EMG median frequency and
70
recrui tment of muscle f ibres was based solely on the assumption
that EMG median f requency is ref lected in muscle f ibre conduct ion
veloci ty. Conduct ion veloci ty is also sensi t ive to changes in muscle
f ibre diameter rather than just f ibre type and changing muscle length
dur ing contract ion would also al ter muscle f ibre diameter (McHugh et
a l . , 2002b). Previous studies (Bazzy et a l . , 1986, Potvin, 1997)
have shown that isometr ic contract ions have less ef fect on the f ibre
diameter than other types of contract ion. Isokinet ic contract ion as
used in the study by McNair and Wood (1993) may have contr ibuted
to inaccuracy and more l imi ted rel iabi l i ty in the EMG median
frequency measure as a funct ion of changes in muscle length and
f ibre diameter. Therefore, select ion of a mode of contract ion with no
change in length dur ing muscle act ion would in theory produce the
most stable EMG median f requency. This ensures that any change
in f ibre s ize is due solely to the hypert rophy or at rophy instead of a
resul t of a change in muscle length.
Previous research (Pincivero et a l . , 2001, Koumantakis et a l . ,
2001a) have suggested that i f an equal intensi ty of muscle
contract ions was performed bi lateral ly wi thout causing fat igue,
isometr ic contract ion at any intensi t ies did not af fect the bi lateral
symmetry of the EMG median frequency. Equal intensi ty of muscle
contract ions is most accurate ly and easi ly obtained at their maximal
ef forts. Therefore maximum voluntary isometr ic contract ion (MVIC)
can be used to produce the EMG median frequency provided that the
durat ion of contract ion can be careful ly monitored without causing
fat igue.
71
Although a considerable number of studies have examined the
rel iabi l i ty of determining EMG resul ts, the major i ty conducted test
and re-test procedures on di f ferent days, def ined as inter-bout
rel iabi l i ty (Koumantakis et a l . , 2001b, Bi lodeau et al . , 1994, Ng et
al . , 1996, El fv ing et al . , 1999, McHugh et al . , 2001, Biedermann et
al . , 1990, Dedering et al . , 2000, Taylor et a l . , 1997b). In contrast ,
fewer studies have evaluated the intra-bout rel iabi l i ty , that is , the
test-retest re l iabi l i ty wi th respect to the stabi l i ty of the EMG median
frequency across consecut ive t r ia ls (McHugh et al . , 2001, Pinc ivero
et a l . , 2000). Addi t ional ly, there is l imi ted scient i f ic informat ion
concerned with the rel iabi l i ty of the EMG median frequency in
relat ion to the mode and durat ion of muscular contract ion used in
producing this measure.
The main purpose of th is s tudy was to evaluate the rel iabi l i ty of
EMG median frequency under di f ferent condi t ions and in both
extensor and f lexor muscles of the knee. Speci f ical ly the
invest igat ion was designed to:
• Determine the rel iabi l i ty of the EMG median frequency
bi lateral ly and across both extensor and f lexor muscles of the
knee;
• Ident i fy the mode of contract ion associated with the greatest
rel iabi l i ty of EMG median frequency across 5 speeds from 0° to
240° per second; and
72
• Invest igate the ef fects of gender, l imb dominance and the
veloci ty of muscle contract ion on EMG median frequency of
knee extensors and f lexors.
The f indings f rom this study wi l l provide the necessary informat ion
to def ine protocols for later s tages of th is research project .
73
3.2 Methodology 3.2.1 Subjects
Fi f ty- f ive (33 males and 22 females) heal thy subjects between the
ages of 15 and 55 were recrui ted from the students and staf f of
Queensland Universi ty of Technology (QUT) for th is s tudy. The
mean age, weight and height of the male subjects who part ic ipated
in th is study were 23.94 years ± 8.05, 74.33 kg ± 14.15 and 175.00
cm ± 6.25 respect ively. Corresponding values for female subjects
was 27.55 years ± 8.32, 63.89 kg ± 9.71 and 167.44 cm ± 7.94.
There was no signi f icant age di f ference between the two groups
(p>0.05).
Al l subjects were regular part ic ipants in physical act iv i ty but those
volunteers who were sedentary, act ive in sport at an el i te level or
had a record of knee in jury requir ing medical t reatment were
excluded from the study. (See appendix C for the inclusion and
exclusion cr i ter ia) .
3.2.2 Experimental procedure
The evaluation protocol
Al l test ing was conducted in the Physiology Laboratory at the
School of Human Movement Studies at QUT, Kelvin Grove
campus. Each subject was required to at tend one vis i t and to
perform an isokinet ic strength test ing protocol (L i et a l . , 1996)
dur ing which an EMG was recorded. Interfacing of the EMG
74
system with the Kin-Com isokinet ic dynamometer (500H,
Chattanooga) al lowed synchronizat ion of torque, jo int angle and
EMG data which was recorded by an AmLab Data Acquis i t ion
System (Operat ing System I , Version 1.97, Associat ive
Measurement Pty. Ltd. , Sydney, Austral ia) . The detect ion of
the EMG signal and the evaluat ion of the muscle strength were
performed simultaneously using the Kin-Com isokinet ic
dynamometer (Figure 3.1). The EMG data were analysed
fol lowing the protocol used in an ear l ier evaluat ion of the EMG
median f requency (McNair and Wood, 1993) of the quadr iceps
and hamstr ings of both l imbs.
Consent and screening
Pr ior to any test ing, al l subjects were provided with detai ls of
the invest igat ion including a thorough explanat ion of the nature
of the project , the test ing procedures and the r ights and
consequences of part ic ipat ion in the exper iment. They were
then invi ted to s ign a consent form in accordance with the
Nat ional Heal th and Medical Research Counci l (NH&MRC)
guidel ines for human exper imentat ion. An in i t ia l c l in ical
assessment of the lower l imbs was conducted by the
invest igator to determine the sui tabi l i ty of the subjects by
reference to the inclusion and exclus ion cr i ter ia (Appendix C).
A PAR-Q form was used to ident i fy those subjects who may be
at r isk of cardiac problems dur ing the test procedure (see
Appendix F). Lower l imb dominance was determined by asking
75
the subjects to ident i fy the preferred leg for k icking. Each
subject was then assigned an ident i ty number consecut ive wi th
the previous subject which was used to decide the side of the
leg and the mode of contract ion to be tested f i rst . Subjects
were assigned to tests according to their ident i ty number so as
to select their in i t ia l test ing condi t ion and the pattern of
a l ternat ion between isometr ic and isokinet ic modes and
between dominant and non-dominant l imbs. The contra- lateral
l imb was evaluated in the same way for al l subjects and the
data used for comparison.
EMG median frequency determination procedure
Pr ior to the measurement of isokinet ic strength and recording of
EMG, the subjects performed a 5 minute warm-up session of the
lower l imbs to minimize the r isk of muscular skeletal in jury. The
warm-up movements were simi lar for al l subjects. Subjects
performed approximately 5 minutes of s tat ic cycl ing, fo l lowed by
a 5- minute lower l imb stretching exercise . EMG signal were
recorded by surface EMG using bipolar electrodes (Figure 3.2).
The electrodes used in the project were bi-polar wi th posi t ive,
negat ive and earth poles, al l mounted in a smal l box 30 x 15 cm
in s ize and 3 mm thick. The inter-polar dis tance was 20 mm
between the posi t ive and negat ive poles, and 17 mm between
the earth and the act ive poles. The electrode was designed to
provide a constant inter-electrode (polar) d is tance that was
suff ic ient to avoid cross ta lk ef fects and any unnecessary noise
which may af fect the accuracy of the resul ts , and the distance
76
of 20 mm was considered appropr iate. The consistency of the
inter-polar distance also increases the rel iabi l i ty of determining
the EMG median frequency. The relat ively smal l s ize and
thickness of the electrode was designed for pract ical purposes
and to reduce the anchor ing problem dur ing exerc ise, which
may interfere wi th the ef fect iveness of the muscle contract ion.
Pr ior to the appl icat ion of the electrodes, the skin was prepared
using standard procedures (Zipp, 1982, Pincivero et a l . , 2000).
This involved shaving of the skin areas over the muscle bel l ies
of the vastus lateral is, medial hamstr ings and vastus medial is
(VL, MH and VM) and cleaning by alcohol swabs unt i l the area
was sebum free. The bipolar surface e lectrodes were smeared
with conduct ion gel , at tached to the skin wi th double-sided
adhesive tape over bel l ies of the muscles and secured by
micropore tape (Figures 3.3 to 3.5). The electrodes were
placed over the junct ion between the upper and middle th i rds of
the l ine jo in ing the anter ior super ior i l iac spine (ASIS) and the
proximal border of the patel la, and l ikewise over the junct ion
between the upper and the middle th i rds of a l ine jo in ing the
ischial tuberosi ty and the medial epicondyle of the femur for the
measurements of VL and MH respect ively. For VM, the
electrode was placed over the mid point between the adductor
tubercle of the femur and the proximal border of the patel la.
These electrodes were in turn connected to the AmLab EMG
Data Acquis i t ion System and a 3-channel ampl i f ier (Qantec,
PTS Pty. Ltd. , Queensland) (Figure 3.1). This provided the
hardware for bandpass f i l ter ing (20 to 500 Hz) and ampl i f icat ion
77
(x 800 gain) of the EMG signals. Electromyographic s ignals
were then sampled at 1000 Hz with a resolut ion of 9.15 x 10-6
vol ts and downloaded to the AmLab Data Acquis i t ion System
(Figure 3.1). In terfacing of the isokinet ic dynamometer (Kin-
Com) with the AmLab EMG Data Acquisi t ion System also
enabled measurement of knee jo int torque and angles to be
synchronised with the EMG data.
Af ter col lect ing the EMG data, a LabVIEW Version 6i Software
program (Data Acquisi t ion & analysis for the Movement
Sciences by A. L. McDonough) was used to determine the EMG
median frequency. First ly, the 1000-mi l l isecond sect ion of the
s ignal containing the maximum root-mean-square (RMS) was
found by running a LabView rout ine. This sect ion of the raw
EMG signal was then weighted with a Hanning Window and zero
padded to a length of 1024 samples before apply ing an FFT
rout ine to provide the frequency spectrum. The Hanning
window was programmed to s l ide at a 1-mi l l isecond step. The
total area under the spectrogram was calculated using
integrat ion. The median f requency was determined as the X-
axis f requency value that div ides the area under the curve in
hal f (See Figures 3.6 to 3.12). This process was used to
determine the mean EMG median frequency bi lateral ly for the
VL, MH and VM, which were ta l l ied for a l l 55 subjects.
78
Calculation of bi lateral discrepancy
The percentage bi la teral d iscrepancy in EMG median f requency
between muscle groups of each l imb was calculated by d iv id ing
the absolute di f ference between the paired EMG median
frequencies by the higher of the two values, then mul t ip ly ing the
resul t by 100 to convert into a percentage value.
Isokinetic testing protocol
A Kin-Com 500H isokinet ic dynamometer was used to measure
the isokinet ic s trength of the quadr iceps and hamstr ings
muscles of both lower l imbs. An isokinet ic test ing protocol
based on an ear l ier protocol developed by the invest igator (Li et
a l . , 1996) was used in th is measurement wi th minor
modif icat ions. Five tr ia ls of 8-seconds durat ion isometr ic
contract ions of the quadr iceps and hamstr ings at 45° of knee
f lexion were included. The per iod of 8-second for the isometr ic
contract ion was used by reference to previous research which
indicated that the durat ion of contract ion should be long enough
to ensure complete muscle f ibre recrui tment. This lasts for 2
seconds and is stable for 6 seconds without causing fat igue
(Lar iv iere at al . , 2001).
The subject was posi t ioned and secured in the Kin-Com
dynamometer (F igure 3.1). Pr ior to the test ing, the range of
79
motion (0° to 90°) of the knee jo int was cal ibrated using a spir i t
level and the Kin-Com goniometer. The subject was then
instructed to perform several sub-maximal ef fort knee
movements through the ent i re range of f lexion and extension.
This served to fur ther warm up the knee to al low the subject to
become fami l iar wi th the Kin-Com isokinet ic machine. The
subject 's leg was then posi t ioned at the preset 45° of knee
f lexion as measured by the Kin-Com dynamometer. An 8-
second maximum isometr ic contract ion of the quadr iceps was
performed at th is posi t ion, fo l lowed immediate ly by an 8-second
maximum isometr ic contract ion of the hamstr ings at the same
posi t ion. Subjects were then instructed to perform a set of 5
t r ia ls of knee extension and f lexion movements wi th maximum
effort throughout the ent i re knee range (0° to 90°) at an angular
speed of 60° per second. The procedure was repeated 3 t imes
at angular speeds of 120°, 180° and 240° per second with a 1-
minute rest per iod between speed t r ia ls as recommended by
previous researchers (Chan et al . , 1996). The per iod of
maximum contract ion was used for fur ther analysis of the
isometr ic contract ions, and for the dynamic contract ions, the
sect ion of EMG signal containing the maximum RMS value was
used. The maximum RMS value was detected by the LabView
software program (Version 6i , A.L. McDonough, 2001).
Consistent verbal encouragement was given throughout the
whole per iod of test ing. The same procedure was repeated on
the other leg af ter a 5-minute rest per iod. Subjects who were
assigned to be tested with the isokinet ic mode f i rst had the
sequence of test ing modes reversed. However, wi th in the
80
dif ferent speeds associated with the dynamic contract ions, i t
was not considered necessary to randomise the test ing
sequence. I t was considered that the possibi l i ty of producing
fat igue af ter 5 repet i t ions of dynamic contract ions was minimal
part icular ly as a 60-second rest per iod was taken between each
dynamic speed condi t ion.
3.2.3 Statistical analysis
The means, standard deviat ions and the between tr ia ls standard
deviat ion of the EMG median frequency obtained from the muscle
contract ions of each leg and the bi lateral d iscrepancy of the EMG
median f requency were stat ist ical ly analysed using SPSS for
Windows 10.0 Vers ion. Descr ipt ive stat ist ics were represented by
the means and standard deviat ions. T-tests were performed to
compare the di f ferences in EMG median frequency between male
and female subjects and between dominant and non-dominant l imbs.
A mult ivar iate 2 x 3 mixed model of ANOVA with Tukey Post-hoc test
was performed to compare di f ferences between the veloci ty of
muscle contract ion on EMG median frequency of knee extensors and
f lexors. The level of s igni f icance was set at p<0.05.
81
F ig 3 .1 A p re-ampl i f i ed e lec t rode connected to the AmLab EMG Acqu is i t ion Sys tem v ia a Qantec Ampl i f i e r
F ig 3 .2 A pre-ampl i f i ed b ipo lar su r face e lec t rode used in a l l t h ree s tud ies .
82
F ig 3 .3 P lacement o f p re-ampl i f i ed b ipo la r sur face e lec t rode fo r r igh t vas tus la tera l i s
F ig 3 .4 P lacement o f p re-ampl i f i ed b ipo la r sur face e lec t rode fo r le f t med ia l hamst r ings
F ig 3 .5 P lacement o f p re-ampl i f i ed b ipo la r sur face e lec t rode fo r le f t vas tus med ia l i s
83
Fig 3 .6 A t yp ica l EMG tes t record showing the jo in t ang le , t he EMG s igna l and the to rque o f the vas tus la tera l i s in the f i rs t , second and th i rd rows respec t ive l y
84
F ig 3 .7 D i rec t EMG s igna l f rom vas tus la tera l i s showing the p rocedure to detec t the segment wi th the h ighes t va lue
85
Fig 3.8 A typ ica l f requency d is t r ibut ion curve produced by FFTThe dark ver t ica l l ine d iv ides the area under the curve in to equal ha lves and d iv ides the X ax is to g ive the va lue o f the median f requency (65.34 Hz)
86
Locate e slidingwindow 000ms)
etect highest
RMS
Transform the
EMG data
Frequency
distribution
curve by FFT
Calculate area
under curve
Halving area
under curve
EMG dian
fre ncy
Fig 3 .9 D i f fe tages in the determinat ion o f the med ian f requency f rom d i rec t EMG s igna ls
th (1
ren t s
D
87
Me
que
Fig 3.10 Schematic diagrams showing the EMG median frequency
t ransformat ion process from raw EMG signals.
88
Fig 3.11 A typical raw EMG signal generated f rom a 60°/second isokinet ic extension and f lexion contract ion using the Kin-Com dynamometer. The whi te EMG curve represents vastus lateral is , green curve vastus medial is, and red curve medial hamstr ings. the RMS of the EMG signals are recorded in the three meters at the r ight lower corner.
89
F ig 3 .12 A typ ica l EMG MF graph showing the b i la tera l d isc repancy.
90
3.3 Results
, 120°, 180°, and
40°/second respect ively) . As shown in Table 3.1, the lowest
a t ren entage bi lateral d iscrepancy
i th increased test ing speeds. However, no signi f icant correlat ion
3.3.1 The EMG median frequency The mean EMG median frequency in hertz (Hz) and the percentage
bi lateral d iscrepancy of VL, MH and VM of a l l subjects are shown in
Tables 3.1. Values for the EMG median frequency ranged from 60.0
± 11 Hz to 69.0 ± 14 Hz and were independent of the speeds of
contract ion (p=0.367). There were no signi f icant bi latera l
d i f ferences in th is measure at any of the 5 speeds of contract ion
used (p=0.97, 0.99, 0.36, 0.33, and 0.30 at 0°, 60°
2
percentage bi lateral d iscrepancy was recorded at 0° per second with
d towards an increase in the perc
w
was found between the change in the mean EMG median frequency
and the change in test ing speeds (r=0.524 p>0.05). When the 3
muscles were examined indiv idual ly, th is t rend was st i l l apparent
(Table 3.2, Figure 3.13).
Table 3.2 shows the mean EMG median frequency measures for the
VL, MH and VM (see also Figures 3A.1 to 3A.3 in Appendix A).
When comparing the EMG median frequencies of the 3 muscles, an
elevat ion of mean EMG median f requency was observed in vastus
medial is muscle at a l l speeds of test ing (see Figures 3A.4 to 3A.8 in
Appendix A). This observat ion was the same for both male and
female subjects (Table 3.3) when the resul ts of male and female
subjects were examined separately.
91
3.3.2 Gender and bilateral EMG median frequency comparison
No signi f icant bi la teral d i f ferences were found in the mean EMG
median f requency of VL, MH and VM at al l the test ing speeds (p=
0.33-0.99 Table 3A.3 in Appendix A) (Table 3.4). Measures of the
ercentage bi lateral d iscrepancy for male and female subjects when
examined separately are shown in Table 3.4 and Figure 3.15. (see
Figures 3A.9 to 3A.14 in Appendix A). No gender di f ferences in
EMG median frequency were found which permit ted the combining of
male and female subjects in subsequent analyses.
3.3.3 Between tr ials standard deviation of EMG median frequency
within a bout of muscle testing
Figure 3.14 and Table 3A.1 in Appendix A show the average between
tr ia ls standard deviat ion for EMG median frequency measured dur ing
a bout of 5 t r ia ls in the selected muscles of a l l subjects at d i f ferent
speeds (n=55). The between tr ia ls standard deviat ion ranged from
4.50 to 7.92 with the lowest between tr ia ls standard deviat ion
recorded at 0° per second. Table 3A.2 and Figure 3A.26 in Appendix
A show the between tr ia ls standard deviat ion of the EMG median
frequency of VL, MH and VM when the 3 muscles were examined
indiv idual ly. Between tr ia ls var iabi l i ty was signi f icant ly lower at 0°
per second ( isometr ic contract ions) and 60° per second than at other
contract ion speeds. Between tr ia ls standard deviat ion of the EMG
median frequency of the vastus media l is muscle was elevated at a l l
the contract ion speeds when compared to that of the vastus lateral is
and medial hamstr ings (Table 3A.2) and (see Figures 3A.15 to 3A.19
p
92
in Appendix A). The elevat ion of the between t r ia ls standard
eviat ion of EMG median frequency in vastus medial is relat ive to the
nt knees
(Tabl pendix A), or the resul ts of the male and female
(T .2 min ep
d
other muscles remained when non-dominant and domina
e 3A.2 in Ap
able 3 ) were exa ed s arately.
93
Table 3.1 Mean EMG MF in Hz and the mean percentage bi lateral d iscrepancy (% f V VM of a sp
Sp ds)
Non-Dominant SD Dominant SD % BD* SD
BD) o L, MH and combined al l subjects t d i f ferent eeds
ee (°/s
0 65 12 65 11 4 .01 3 .06
60 69 13 69 14 7 .22 7 .83
120
61 63 1 12.57
0 64 15 62 14 23.80 13.76
60 11 61 12 12.66 9 .06
180 12 3 19.20
24
(n= *%BD = (Max-Min) /Max x 100% Ta 2 M MF th D iv leMH and VM of al l subjects at di f ferent speeds
(° /s) n-
Dom SD Dom SD Individual
% BD* SD
55)
ble 3. ean EMG in Hz and e mean %B of each ind idual musc of VL,
Speed No
VL 0 59 9 59 7 5 4
60 64 10 64 12 9 12
59 9 9 11 9
18 59 11 19 14
240 60 12 59 21 15
MH 0 62 10 62 10 4 3
60 63 12 64 6 5
120 58 10 5 9 12 9
18 60 12 9 17
24 62 14 12 24
0 73 11 10 3 2
60 79 11 13 6 4
12 62 13 15 15 9
18 65 12 17 22
240 69 16 67 27 13
120 10 5
0 11 60
12
11
9
0 60 10
0 59 13
VM 73
79
0 65
0 68 13
16
(n= %BD = (Max-Min) /Max x 100%
55) *
94
Table 3.3 Mean EMG MF in Hz and the standard deviation (± SD) of VL, MH and VM of male and female subjects at different speeds
VL(SD) MH (SD) VM (SD) VL (SD) MH (SD) VM (SD)
Speeds (° /s)
Male Non-Dom Dominant
0 60 . 3 (8 . 3 ) 61 . 6 (9 . 9 ) 73 . 2 (1 1 .8 ) 60 . 1 (7 . 4 ) 61 . 9 (9 . 6 ) 73 . 2 (1 1 .1 )
60 63 . 4 (1 1 .5 ) 63 . 8 (1 2 .2 ) 79 . 0 (1 1 .2 ) 63 . 2 (1 3 .6 ) 64 . 5 (1 1 .3 ) 79 . 1 (1 2 .2 )
120 59 . 9 (1 1 .5 ) 57 . 6 (9 . 9 ) 65 . 0 (1 2 .6 ) 61 . 3 (8 . 6 ) 58 . 8 (9 . 3 ) 67 . 0 (1 4 .1 )
180 60 . 3 (1 1 .8 ) 60 . 4 (1 2 .0 ) 65 . 8 (1 3 .0 ) 62 . 1 (1 0 .0 ) 58 . 7 (9 . 6 ) 68 . 8 (1 7 .2 )
240 61 . 4 (1 1 .1 ) 61 . 9 (1 6 .0 ) 70 . 8 (1 5 .7 ) 58 . 5 (1 2 .1 ) 59 . 6 (1 1 .4 ) 68 . 8 (1 5 .2 )
Female Non-Dom Dominant
0 57 . 1 (8 . 7 ) 62 . 9 (9 . 8 ) 73 . 1 (1 0 .1 ) 57 . 3 (7 . 3 ) 62 . 9 (9 . 7 ) 73 . 1 (9 . 6 )
60 65 . 3 (8 . 0 ) 62 . 0 (1 1 .0 ) 80 . 0 (1 1 .9 ) 64 . 5 (7 . 7 ) 62 . 4 (9 . 8 ) 79 . 5 (1 3 .6 )
120 58 . 0 (7 . 9 ) 58 . 2 (1 0 .4 ) 58 . 3 (1 3 .9 ) 56 . 4 (9 . 8 ) 59 . 0 (7 . 6 ) 61 . 0 (1 6 .4 )
180 58 . 0 (9 . 2 ) 59 . 0 (1 0 .9 ) 64 . 3 (1 2 .0 ) 57 . 9 (1 2 .6 ) 62 . 7 (7 . 6 ) 66 . 2 (1 6 .3 )
240 57 . 1 (1 3 .4 ) 61 . 1 (1 0 .5 ) 67 . 4 (1 6 .7 ) 60 . 7 (1 . . 6 ) 58 . 6 (1 2 .6 ) 64 . 8 (1 7 .3 )
Ma le n=33, female n=22 Tab le 3 .4 Mean %BD and the s tandard dev ia t ion o f EMG MF o f VL, MH and VM of male and female sub jec ts a t d i f fe rent speeds .
Muscle Speeds
(° /s) Male
% BD* SD Female %BD* SD
VL 0 5 .2 5 3 .8 9 4 .8 3 3 .8 3
60 11 . 10 14 . 76 6 .6 4 4 .4 0
120 8 .9 9 7 .0 2 13 . 81 9 .9 3
180 19 . 42 12 . 85 17 . 30 16 . 26
240 19 . 31 13 . 27 23 . 40 16 . 46
MH 0 3 .2 4 2 .5 5 4 .0 8 2 .5 3
60 5 .8 8 4 .6 4 6 .7 1 4 .6 4
120 12 . 11 9 .9 9 11 . 69 7 .5 2
180 15 . 48 10 . 14 19 . 13 10 . 57
240 23 . 36 11 . 32 24 . 14 15 . 24
VM 0 3 .4 1 2 .3 6 3 .3 4 2 .3 3
60 6 .0 5 3 .8 9 6 .2 9 4 .4 4
120 15 . 16 9 .4 8 15 . 08 9 .0 7
180 23 . 10 11 . 03 20 . 58 14 . 57
240 24 . 35 11 . 92 30 . 46 14 . 71
Male n=33, female n=22 *%BD = (Max-Min ) /Max x 100%
95
0
5
10
15
20
25
30
0 60 120 180 240
Speeds in degree per second
% B
ilate
ral D
iscr
epan
cy
VL MHVM
o f VL, MH and VM of a l l
ub jec ts a t d i f fe rent speeds n 5
Fs
ig 3 .13 Mean b i la tera l d isc repancy (BD) o f EMG MF
=5
4
5
6
7
8
9
10
0 60 120 180 240
Speeds in degree per second
SD B
etw
een
Rep
etiti
ons
VLMHVM
F ig 3 .14 Between t r ia l s s tandard dev ia t ion (BTSD) o f EMG MF of VL, MH and VM of a l l sub jec ts a t d i f fe rent speeds n=55
96
0
5
10
15
20
0 60 120 180 240
la d
ian
25
Speeds in degree per second
% B
ite
ral
scre
pc
30
y
MaleFemale
F ig 3 .15 Percentage b i la tera l d isc repancy o f EMG MF of the a l l musc les in ma le and in fema le sub jec ts a t d i f f e rent speeds (ma le n=33, female n=22)
8
9
11
12
13
14
Speeds in degree per second
een
rails
Sta
nda
Dev
iatio
n
10
15
0 60 120 180 240
Bet
w T
rd
DomN-Dom
Fig 3 .16 BTSD o f EMG MF o f a l l musc les o f t he non-dominant and dominant
l imbs o f a l l sub jec ts a t d i f fe rent speeds (n=55)
8
9
0 60 120 180 240
Speeds in degree per second
Bet
wee
n T
ials
10
11
12
r S
tand
ard
ati
13
14
Dev
ion
Male
Female
speeds (ma le n=33, female n=22)F ig 3 .17 BTSD o f EMG MF o f a l l musc les o f ma le and fema le sub jec ts a t d i f fe ren t
97
3.4 Discussion and summary
The purpose of th is study was to determine the rel iabi l i ty of EMG
ty of EMG
median frequency across 5 speeds f rom 0° to 240° per second.
ve loci ty of muscle f ibre at varying speeds
of contract ion and l imi tat ion in EMG data analysis procedures have
median f requency bi lateral ly and across both extensor and f lexor
muscles of the knee. An addi t ional a im was to ident i fy the mode and
durat ion of contract ion associated with the greater rel iabi l i
No signi f icant bi lateral d i f ferences were found in the EMG median
frequency at any of the f ive speeds of contract ion. Consequent ly,
both the dominant and non-dominant l imb can be taken as a contro l
for comparisons with the other l imb fol lowing an intervent ion
involving that l imb, or changes in i ts funct ional status fol lowing
in jury. The resul ts also indicated that for VL, MH and VM, the lowest
bi lateral d iscrepancy in EMG median frequency occurred dur ing
isometr ic contract ions. Mean data showed a t rend toward increased
bi lateral d iscrepancy of EMG median frequency as the test ing speed
increased through 60°, 120°, 180°, and 240° per second. This
observat ion also occurred in both male and female subjects when
the three muscles were examined separately. None of these t rends
in mean data were found to be stat is t ical ly s igni f icant.
The f inding of the tendency of reduced rel iabi l i ty in the EMG median
frequency with increasing speed of contract ion is consistent wi th the
resul ts of ear l ier studies (McHugh et al . , 2002b, Potvin, 1997).
Var iat ion in the conduct ion
98
been suggested as possible reasons for d i f ferences in the rel iabi l i ty
of the median f requency with increasing speed (Kupa et al . , 1995)
Consistent wi th ear l ier research (Potvin, 1997), between tr ia ls
var iabi l i ty was lower dur ing isometr ic contract ions in contrast to the
si tuat ion which occurred as the test ing speed increased.
EMG median f requency has also been shown to be associated wi th
the conduct iv i ty of the muscle f ibre (Sadoyama et al . , 1983, Taylor
et a l . , 1997b) which in turn is related to the d iameter of the f ibre
(Broman et a l . , 1985, Taylor et a l . , 1997b). Changes in muscle f ibre
diameter may be related to the change of muscle length which
occurs dur ing a dynamic muscle contract ion (McHugh et a l . , 2000).
The reduced var iabi l i ty which is a potent ia l factor for the di f ference
in rel iabi l i ty , in the EMG median f requency associated with the
isometr ic mode of contract ion may be explained by the lack of
change in muscle f ibre length and diameter. This may explain the
observat ion that re l iabi l i ty decreased as test ing speed increased as
ate of change in muscle length is greater at faster speeds. Other r
invest igators have suggested that when apply ing the FFT algor i thms,
a sui table sect ion of the EMG signal should be selected such that i t
is consistent in ampl i tude (McHugh et a l . , 2001). I t was
hypothesized by the same authors that the stabi l i ty of the EMG
signal is more d i f f icul t to maintain dur ing dynamic contract ions in
contrast to the isometr ic mode. The resul ts of the present study also
conf i rm th is hypothesis.
99
Several s tudies have examined the rel iabi l i ty of a broad range of
EMG parameters including median frequency, mean power and root
mean square (RMS). The major i ty of these test and re-test studies
evaluated ei ther the inter-session rel iabi l i ty (between days)
(Linnamo et al . , 2000, Merlet t i et a l . , 1998, Biedermann et al . , 1990,
Dede g et a l . , 2000, Taylor et a l . , 1997a, Thompson and
demonstrated that the vastus lateral is y ie lded signi f icant ly higher
EMG median frequencies than vastus medial is in groups of heal thy
r in
Biedermann 1993, Bi lodeau et al . , 1994, Koumantakis et a l . , 2001b,
McHugh et al . , 2001), or intra-session rel iabi l i ty (between bouts
wi th in the same session) (Davis et a l . , 1998). Previous studies have
only evaluated the reproducibi l i ty of EMG median frequency on
separate occasions (bouts) (Bi lodeau et a l . , 1994, Ng et a l . , 1996,
Koumantakis et a l . , 2001b, McHugh et al . , 2001, Dedering et al . ,
2000, Taylor et a l . , 1997a) and only a l imi ted number of studies have
examined the rel iabi l i ty of successive contract ions. Consistent wi th
an ear l ier study (Pincivero et a l . , 2000), an associat ion was found
with the EMG median frequency value and the var iabi l i ty between
tr ia ls wi th in a bout. In both studies, resul ts showed that di f ferent
muscles y ie lded di f ferent rel iabi l i ty values.
In agreement wi th ear l ier studies (Koumantakis et a l . , 2001b,
Pincivero et a l . , 2000), no signi f icant di f ferences were found in the
EMG median frequency between male and female subjects.
However, in the present study, there was an elevat ion of the EMG
median frequency in the vastus media l is muscle of both l imbs, in
both male and female subjects and at a l l contract ion speeds. This
was in contrast to a previous research (Pincivero et a l . , 2000) which
100
male and female subjects. This discrepancy in resul ts may ref lect
methodological d i f ferences part icular ly wi th respect to electrode type
and conf igurat ion. These di f ferences in e lectrode design and
circui t ry may have produced di f ferent f i l ter ing ef fects of the EMG
signals (Pincivero et a l . , 2000).
In the present study, the s igni f icant ly lowest var iabi l i ty in EMG
median frequency between successive t r ia ls of muscle contract ions
occurs at 0° per second ( isometr ic) for al l the three muscles. Among
the three muscles, vastus medial is showed the greatest var iabi l i ty
between tr ia ls. This resul t d i f fered from that of an ear l ier
invest igat ion (Pincivero et a l . , 2000), which showed that the
var iabi l i ty observed for the EMG median frequency dur ing three
successive isometr ic contract ions was highest for vastus lateral is
than rectus femoris and vastus medial is . A possible explanat ion for
the contradictory resul ts may l ie in the method of calculat ing the
EMG median f requency. An FFT of 512 points was performed on 11
consecut ive, 512 mi l l iseconds segment, over lapping each other by
hal f their length (256 mi l l iseconds) for each 3-second contract ion.
The EMG median f requency was determined from each of the 11
over lapping windows. In the present study, a s l id ing window of 1000
mi l l iseconds was used to sweep through the EMG signal of the ent i re
contract ion in 1-mi l l isecond steps to detect the segment wi th the
highest EMG RMS value. The di f ference in the Four ier
t ransformat ion of the EMG data into the f requency dist r ibut ion graph
may yield di f ferent median frequency values (Kar lsson et a l . , 2000).
101
Another possible reason for the discrepancy of resul ts between the
two studies was the durat ion of isometr ic contract ion dur ing which
EMG data was recorded. In an ear l ier study (Pincivero et a l . , 2000)
th is as a consequence of using a f ixed window of a
speci f ied length for a l l speeds of muscle test ing. This explains why
f th is study show that when using the present protocol ,
the isometr ic mode was more rel iable than the isokinet ic mode. One
of
most
a contract ion per iod of 3 seconds was used in contrast to 8 seconds
in the present study. Fast twi tch motor uni ts are recrui ted
progressively (McHugh et al . , 2002b) and di f ferent muscles require
di f ferent lengths of t ime to be ful ly recrui ted. At any given t ime
dur ing the contract ion per iod, a varying proport ion of f ibres would be
involved, resul t ing in di f ferent outcomes. Predictably, when the
muscle is not fat igued, fu l ler muscle f ibre recrui tment occurs at the
later phase of the contract ion than at the ear l ier phase.
The present study involved muscle contract ion speeds ranging f rom
0° to 240°per second and the t ime to complete one cycle of
movement lasted f rom 8000 mi l l iseconds in the case of isometr ic
contract ion to 375 mi l l iseconds in the case of 240° per second. A
1000-mi l l isecond window may include some quiet muscular act iv i ty
segments. Whi le th is is not an ideal case, i t is however, very
di f f icul t to avoid. Nevertheless, the analysis was anchored to the
peak RMS EMG at which highest muscle act iv i ty and greatest muscle
f ibre recrui tment were expected. To a certain extent one may have
to accept
the resul ts o
the major aims of the present study was to object ively ident i fy the
appropr iate mode of muscle contract ion for the determinat ion
102
of EMG median frequency. Consequent ly, isokinet ic mode was not
rec
In the
used
used ch inc lude the Hamming, Hanning,
Rect ngular, Bart le t t , (s imi lar to Daniel l ) windows. A pi lot t r ia l
des
signal
resul t d ix F). I t is unl ikely that the use of di f ferent
wind ws signi f icant ly inf luenced the resul ts. A 1000-mi l l isecond
sam
would
other
calcul d to the 1000-
mi l l isecond window method, as wel l as var iat ions depending on the
locat ion of the 1000-mi l l isecond window. This window al lows the
procedure to analyse the signal segment that corresponds to the
per iod of greatest muscle f ibre recrui tment. To compromise between
the best resolut ion and least var iat ion, a 1000-mi l l isecond sl id ing
Hanning window was therefore adopted in the methodology of th is
study.
In summary
Isometric contraction was found to be the most reliable mode for
determining median frequency and consequently wil l be used in
subsequent parts of this study.
ommended.
present s tudy, a 1000-mi l l isecond sl id ing Hanning window was
in the determinat ion of EMG median f requency. Commonly
windows in recent resear
a
igned to determine the median frequency of raw EMG sample
s us ing the above ment ioned four windows yielded very s imi lar
s (see Appen
o
pl ing was used in th is study and gave a resolut ion of 1 Hz which
be suff ic ient in improving the resolut ion beyond 1 Hz. On the
hand, a di f ference exists in the EMG median frequencies
ated from the whole s ignal as compare
103
No signif icant bila re found in the EMG
median frequency of VL, MH Consequently, in future
b
under normal condit ions.
No gender differences were found in the EMG median frequency
teral differences we
, and VM.
studies in which the EMG median frequency is used, the
contralateral l imb can act as a control for the experimental l im
for any of the muscles tested irrespective of the speed of
contraction.
Signif icant differences were found in the EMG median frequency
between muscles, which suggests that when determining the
measure in a muscle group such as the quadriceps, it is advised
each muscle may be considered individually.
104
Chapter Four
EMG median frequency changes of vastus lateralis in
response to different speeds of fatiguing exercise
4.1 Introduction
As indicated in previous research, a shi f t in the centra l tendency
measures of the EMG power spectrum is associated wi th the
conduct ion veloci ty of the muscle f ibres (Biedermann et al . , 1990,
DeLuca 1985, Masuda et a l . , 2001) which in turn is associated wi th
the type of muscle f ibre involved (Gerdle et a l . , 1988, Kupa et a l . ,
1995, Wrest ing et a l . , 1987). This research suggests that EMG
median frequency can be used to indicate the proport ion of smal ler
s low twi tch f ibres ( type I) and larger fast twi tch f ibres ( type I) in the
muscle. Warren and col leagues (2000) conf i rmed that a decrease in
the EMG median frequency, represent ing a shi f t to the lef t of the
EMG frequency spectrum, was associated with an increase in the
rat io of smal l to large muscle f ibres. This d irect ional shi f t may
represent a decrease in the proport ion of type I I f ibres or an
increase in the proport ion of type I f ibres. The phenomenon of the
EMG median frequency shi f t to the lower f requency is not only
observed in t ra ining exercise but also immediately af ter fat iguing
exercise, (Arendt-Nielsen et a l . , 1988, Lowery et a l . , 2002, Linnamo
et al . , 2000, Masuda et al . , 1999, Sadoyama et al . , 1981, Warren et
a l . , 2000) indicat ing a decrease in the conduct ion veloci ty of the
105
muscle f ibre. Based on the size pr inciple, a decrease in the
conduct ion veloci ty may represent ei ther a decrease in the relat ive
proport ion of large f ibres ( type I I muscle f ibre atrophy), or an
increase in the proport ion of smal l f ibres ( type I muscle f ibre
hypertrophy) (Hakansson 1956 as c i ted in McNair and Wood, 1993,
Henneman and Olsen, 1965, DeLuca 1985). However muscle s ize
does not change wi th short term exerc ise and i t has been suggested
(Warren et a l . , 2000) that the decrease in the conduct ion veloci ty of
the muscle in response to the fat iguing exercise may be interpreted
as an increase in the act ivat ion of s low motor uni ts. I t is possible
that the response of the muscle to fat iguing exercise may ref lect
d i f ferences in the speed of the muscular contract ion. In previous
studies, the fat iguing exercise were e i ther isometr ic (Arendt-Nielsen
et al . , 1988, Lowery et al . , 2002, Sadoyama et al . , 1981), isotonic
(Linssen et al . , 1991a, Linssen et al . , 1991b, Masuda et al . , 1999,
Broman et al . , 1985), or s low isokinet ic exerc ise below 120° per
second (Warren et a l . , 2000, Gerdle et a l . , 2000, Linnamo et al . ,
2000). No studies have used fast speed isokinet ic exercise to
induce muscle fat igue and the change in the conduct ion veloci ty or
EMG median frequency in response to fast speed isokinet ic fat iguing
exercise (>180° per second) is st i l l unknown.
I t has been shown that the muscle force-veloci ty relat ionship is
related to the f ibre type in the part icular muscle (Thorstensson et
al . , 1976, Gregor et a l . , 1979). ) . Isokinet ic dynamometers provide
a spectrum of speeds ranging from 0° to 400° per second. One
hundred and eighty degrees per second (180°/s), being the mid
port ion of the range, has been regarded as a d iv is ion for fast and
106
slow speeds and is general ly accepted when performing isokinet ic
exercises. There is a possibi l i ty that both s low and fast muscle
f ibres would be act ivated wi th any speed of exercise. However,
speeds below 180° per second are general ly considered as s low and
exercises in th is range are bel ieved to target s low twi tch f ibres, in
contrast to speeds above 180° per second, when the reverse would
occur. However, th is bel ief requires scient i f ic conf i rmat ion. I t is
hypothesized that an increase in the proport ion of type I I ( fast
twi tch) muscle f ibres occurs af ter long term fast speed training
exercise and an increased act ivat ion of type I I muscle f ibres occurs
in response to fast speed isokinet ic exercise. L ikewise, i t is
possible that an increase in the proport ion of type I (s low twi tch)
muscle f ibres occurs af ter long term slow speed t raining and an
increased act ivat ion of type I muscle f ibres occurs in response to
s low speed isokinet ic exerc ise. At th is t ime there is insuff ic ient
evidence ei ther to conf i rm these assumptions by the direct invasive
biopsy technique, or indirect ly by the non- invasive EMG median
frequency method. More informat ion is required to determine the
c i f ic muscle f ibre types in response to fat iguing
xercises at d i f ferent rates of muscular contract ion.
he purpose of th is study was to invest igate changes in the EMG
as been
involvement of spe
e
T
median f requency of vastus lateral is (VL) in response to isokinet ic
exercise at d i f ferent speeds to the point of fat igue. The relat ionship
between EMG median frequency and fat igue has been extensively
studied (Bigland-Ritchie et a l . , 1981, Potvin, 1997). Dur ing
sustained fat iguing contract ion, the EMG median frequency has been
observed to shi f t towards the lower f requency, which h
107
attr ibuted to a proport ional decrease in muscle f ibre conduct ion
EMG median frequency of a muscle
bre, ei ther type I or I I , is bel ieved to be af fected by fat igue (Stulen
return to the pre-exercise level af ter a per iod of
recovery.
4.2 Methodology
4.2.1
Thir ty
ages
of QU
physic
exclus
(See a on cr i ter ia) .
veloci ty (Merlet t i et a l . , 1990).
f i
and De Luca, 1981, Warren et a l . , 2000, Masuda et a l . , 1999).
Normal ly, muscle f ibres fat igue with exercise, but the response of
part icular types of muscle f ibre to fat iguing exercise of speci f ic
speeds has not been conf i rmed. Previous research has shown that
the conduct ion veloci ty of a muscle f ibre decreases with fat iguing
contract ions (Sadoyama et al . , 1983) and is associated wi th the
phenomenon of decreasing in the EMG median frequency of the
muscle. To ver i fy th is phenomenon, i t is hypothesised that there is a
greater decrease in the EMG median frequency ( further lef t shi f t in
the power spectrum) immediately af ter s low speed (30° per second)
fat iguing exercises than fol lowing fast speed (300° per second)
fat iguing exercise. I t is fur ther hypothesised that the EMG median
frequency wi l l
Subjects
- four heal thy subjects (18 males and 16 females), between the
of 15 and 55 years were recrui ted from the students and staf f
T for th is exper iment. Al l subjects were regular part ic ipants in
al act iv i ty and had no record of knee in jury. The inclusion and
ion cr i ter ia were the same as those ident i f ied in chapter three.
ppendix C for the inclusion and exclusi
108
4.2.2
Al l s
Labo
Grov
for th
as d
expe
exam
with a l lowed synchronizat ion of
torque, jo int angle and EMG data which was recorded by an AmLab
Data
evalu
knee
dyna
Consent and screening
number and lower
l imb dominance was determined by asking the subject to
ident i fy the preferred leg for k icking.
Experimental procedure
ubjects were tested dur ing a s ingle v is i t to the Physiology
ratory of the School of Human Movement Studies at QUT, Kelvin
e. Electromyographic and isokinet ic equipment and procedures
e determinat ion of the EMG median frequency were the same
escr ibed previously in Chapter Three. However, in th is
r iment, only the vastus lateral is muscles of both legs were
ined. As in the previous study, interfacing of the EMG system
the Kin-Com isokinet ic dynamometer
Acquis i t ion System. The detect ion of the EMG signal and the
at ion of muscle strength were performed simul taneously dur ing
f lexion and extension using the Kin-Com isokinet ic
mometer.
The invest igat ion was conducted in accordance wi th the
Nat ional Heal th and Medical Research Counci l (NH&MRC)
guidel ines for human exper imentat ion as descr ibed ear l ier .
Af ter s igning the consent form subjects were al lot ted numbers
which were used to assign them to ei ther a s low or fast speed
exercise group. The order of test ing of dominant or non-
dominant l imb was decided by the assigned
109
of fat iguing exercises.
Theref re the absolute EMG median frequency value of a
The experimental protocol
Pr ior to the test ing, a br ief musculo-skeletal examinat ion of the
lower l imbs was conducted by the invest igator to ensure
subjects were f ree from any pathology that might restr ict their
capaci ty to part ic ipate in v igorous isokinet ic t ra ining. These
tests included the l igament laxi ty test , Carr test for patel lo-
femoral pain, and meniscus torn test . Fol lowing the
examinat ion, subjects were al lowed a few minutes to warm-up
with emphasis on the lower l imbs.
Preparat ion for EMG analysis , recording procedures and
determinat ion of EMG median frequency were as descr ibed in
Chapter Three. In th is s tudy, b ipolar surface electrodes
(Figure 3.2) were p laced over the bel l ies of vastus lateral is at
the junct ion between the upper and lower th i rds of a l ine jo in ing
the anter ior super ior i l iac spine (ASIS) and proximal border of
the patel la (Er ison et al . , 1985). In th is study only the VL was
measured. I t was shown in Study One that the absolute values
for EMG median frequency vary f rom muscle to muscle.
However, the aim of the present study was to invest igate the
muscular changes in terms of EMG median frequency which
occur in response to di f ferent speeds
o
part icular muscle was not a major concern.
110
In the arm-up, subjects performed several sub-maximal ef fort
the ent i re range of knee f lexion and
n to become fami l iar wi th the dynamometer. The knee
c contract ion of the
r iceps for a per iod of 8 seconds from which the EMG
gested that
th is per iod was suf f ic ient to al low complete recovery of EMG
y fol lowing fat iguing exercise (Cornwal l et a l . ,
) . This completed the test ing of one l imb and the
w
movements through
extensio
was then posi t ioned at a preset angle of 45° of knee f lexion as
measured by the Kin-Com dynamometer. This was fol lowed by
a pre-exercise, maximum isometr i
quad
median frequency was determined. The bout of exerc ise to
fat igue was then commenced using knee isokinet ic
extension/ f lexion movements at an assigned speed for a 90-
second per iod. The speed of movement was set at e i ther 30°
per second for the s low exercise group, or 300° per second for
the fast exercise group. The knee extension movement was
performed through the range from 90° to 15° of knee f lexion.
Immediate ly af ter the isokinet ic exercise, the f i rst post exercise
8-second isometr ic contract ion of the quadr iceps was
performed and the measure of EMG median frequency
repeated. The procedure and measurement was repeated af ter
a 7-minute recovery. Reference to the l i terature sug
median frequenc
1994
procedure was repeated on the contralateral l imb using the
opposi te speed to that used in i t ia l ly .
The decrease and recovery of EMG median frequency of the
vastus lateral is af ter the fat iguing exercise was calculated for
each subject and expressed in percentages.
111
4.2.3 Statistical analysis
The mean values and the standard deviat ions of the EMG median
frequency of the vastus lateral is of the female and male subjects
were stat ist ical ly analysed and compared.
For the stat ist ical analysis, Pearson’s Correlat ion was used for the
correlat ional analysis. This al lowed determinat ion of the associat ion
between the percentage decrease in EMG median frequency of
astus lateral is and the percentage drop in the extension torque
f ter fat iguing exercise at any speed. A paired t- test was used to
ost fat iguing exercises. The degree of recovery of the measure of
EMG median frequency was determined by comparison of the pre
exercise score wi th that af ter the 7-minute recove d.
An independent t - test was used to evalu te gender di f fe s.
S a using the SPSS for
Ve n and evel of s ig ance was s p<0.05.
4.3 Res
The me n o e
frequency of the vastus lateralis in Hz of both legs of male, female and
frequency
of the vastus lateralis before receiving fast speed exercise was 84 Hz
and 81 Hz for the males and females respectively. Prior to slow speed
exercise, the means were similar, with males and females recording
v
a
compare the di f ference in EMG median frequency between pre- and
p
taken ry per io
a rence
tat ist ic l a was performed nalysis Windows 10.0
r ios th le n f ici e att
ults
ans and sta dard deviati ns (±SD) of th EMG median
all subjects are shown in Table 4.1. The mean EMG median
112
EMG median frequencies of 86 and 80 Hz respectively. The means
and standard deviation of the percentage drop and percentage
recovery of the EMG median frequency of the vastus later d the
extension torque after fa slow fatiguing exercises of male and
female subjects are shown in Table 4.2. There were no statistical
d r n
the EMG median frequency of vastus lateralis after fast (P=0.052) or
after fast
(p=0.31) or slow (p=0.075) fatiguing exercises between male and
female subjects.
Tab le 4 .1 The mean o f the d MF fo wing fa t igu ing exerc ises tages
e (n=
alis an
st or
iff encer es in the pe centage drop and in the perce tage recovery of
slow (p=0.509) fatiguing exercises, or in the extension torque
d i f f e rences in p re anex ressed in percen
post va lues o f EMGl lo p
Mal 18)
MF Dro F % MFDrop % F p % SM Recover FMF Recover % SMean
SD 10.2 10.4 FG Dro G Recover % F Recover G
25.2 99.9 105.9 SD 7.3 9.5 7.5 10.3
Female (n=16)
Drop % FMF Drop % SMF Recover % FMF Recover % SMF
Mean 18.5 29.6 99.0 101.3 SD 6.5 14.3 6.6 6.6
Drop % FG Drop % SG Recover % FG Recover % SG
Mean 20.4 19.8 99.4 104.3 SD 9.4 7.3 7.8 5.2
24.5 26.5 13.9
98.8 103.9 6.7
Drop %
p % S
% SG
Mean 23.4
FMF=EMG MF of the fas t exerc ise group, SMF=EMG MF of the s low exerc ise group; FG=extens ion torque of the fas t group, SG=extens ion torque of the s low group
113
Table 4 .2 The mean o f the percentage dec rease and recovery o f EMG MF o f the vas tus la tera l i s and o f the ex tens ion to rque o f a l l sub jec ts
Drop % FMF Drop % SMF Recovery% FMF Recovery % SMFMean 20.3 28.0 99.5 99.6
SD 12.08 14.0 8.8 7.5
Drop % FG Drop % SG Recovery % FG Recovery % SG Mean 21.9 22.6 102.7 105.2
SD 8.3 8.8 6.7 8.22 FMF=EMG MF of the fas t exerc ise group, SMF=EMG MF of the s low exerc ise group; FG=extens ion torque of the fas t group, SG=extens ion torque of the s low group
Pre Fast ex MF Pre-Slow ex MF
Tab le 4 .3 The mean (±SD) va lues o f t he p re - fa t igu ing exerc ise EMG MF o f the VL o f ma le (n=18) , female (n=16) and a l l sub jec ts (n=34) . No s ign i f i cant d i f fe rence was shown between the speeds .
Mean (Hz) SD Mean (Hz) SD Male
(n=18) 83.97 11.7 86.39 11.54 Female (n=16) 80.75 10.73 80.00 13.43
All subjects (n=34) 82 Hz 11 83 Hz 13
MF= EM G M F ; e x= e xe rc i s e
114
The mean pre-exerc ise EMG median f requency of the vastus lateral is
of the leg receiving fast speed and slow speed fat iguing exercises
was 84 Hz and 83 Hz respect ively. The mean pre-exercise extension
torque of the legs receiving fast speed and slow speed fat iguing
exercises were 481 Nm and 488 Nm respect ively. There were no
signi f icant s ide to s ide di f ferences in the absolute values of the pre-
exercise EMG median frequency of the vastus lateral is (p=0.60) or
the pre-exercise extension torque (p=0.90).
The means and standard deviat ion of the percentage drop and
percentage of recovery of the EMG median f requency of the vastus
lateral is af ter fast and slow fat iguing exercises of a l l male and
female subjects combined are shown in Table 4.3. The percentage
drop in EMG median frequency was signi f icant ly greater af ter s lower
speed fat iguing exercise (27.90%) than af ter fast speed fat iguing
exercise (20.25%) (p<0.001) (Table 4.3 and Figure 4.2). No
signi f icant di f ferences were shown in the percentage drop in the
extension torque between the two speeds (p=0.71), or in the
percentage recovery of EMG median frequency of the vastus
lateral is, or the torque, between the two speeds (p=0.94).
No signi f icant correlat ions were shown between the age of the
subject and EMG median frequency of the vastus lateral is, or the
extension torque of the same subject . Addi t ional ly, no s igni f icant
associat ion was found between the percentage decrease in EMG
median frequency of vastus lateral is and the percentage drop in the
115
extension torque af ter fat iguing exercise with fast speed (r=-0.05) or
s low speed (r=0.17) (p>0.05).
116
0
5
10
15
20
25
30
% d
rop
in E
MG
MF
and
Torq
ue 35
40
45
Drop % FMF Drop % SMF Drop % FG Drop % SG
*
Fig 4 .1 Percentage d i f f e rences in p re and pos t measures o f EMG MF and torque in re la t ion to fas t and s low exerc ise to fa t i gue o f a l l sub jec ts
* S ign i f i cance p< 0 .001
0
20
40
80
100
Recovery%FMF
Recovery %SMF
Recovery % FG Recovery % SG
60
120
% o
f rec
over
y in
EM
G M
F an
d To
rque
Fig 4 .2 Percentage o f recovery in EMG MF and torque in re la t ion to fas t and
s low exerc ise to fa t igue o f a l l sub jec ts (Recovery = 7 m inutes )
117
4.4 Discussion and summary
The study invest igates the changes in EMG median frequency of
vastus lateral is in response to isokinet ic exercise at d i f ferent speeds
to the point of fat igue. I t was hypothesised that there is a greater
decrease in the EMG median f requency ( further lef t shi f t in the
power spectrum) immediately af ter s low speed (30°per second) than
fol lowing fast speed (300° per second) fat iguing exercise. I t was
further hypothesised that the EMG median frequency wi l l return to
the pre-exercise level af ter a per iod of recovery.
Consistent wi th the resul ts of the previous exper iment and ear l ier
studies, no signi f icant gender (Pincivero et a l . , 2000, El fv ing et a l . ,
2000, Koumantakis et a l . , 2001b) or bi lateral (Nargol et a l . , 1999,
Lindstrom et al . , 1995) di f ferences were found in the EMG median
frequency of the vastus lateral is. In contrast , Mannion et a l . , (1998)
und signi f icant gender di f ferences in the EMG median frequency of
G median frequency
om the erector spinae and i ts indiv idual structural components.
fo
the erector spinae muscles of 17 males and 14 females. I t is
suggested that the di f ference may ref lect the greater representat ion
of type I muscle f ibres in the erector spinae of females and the
increased fat igue resistance as evidenced by a longer t ime to fat igue
in that muscle for the women (Mannion et a l . , 1997). The
di f ferences found between this study and the present one may
represent di f ferences between the resul ts of the structura l
organizat ion of the erector spinae and the quadr iceps and the
relat ively increased di f f icu l ty in determining EM
fr
118
The signi f icant decrease in the EMG median f requency found in the
vastus lateral is when fat igued is consistent wi th ear l ier studies
involving muscles of the lower l imb (Gerdle et a l . , 2000, Linssen et
al . , 1991b, Masuda et al . , 1999, Arendt-Nielsen and Mi l ls , 1988,
McHugh et al . , 2002a, Linstrom et al . , 1995, Warren et al . , 2000,
Cornwal l et a l . , 1994, Potvin, 1997, Big land-Ritchie et a l . , 1981, Tho
et al . , 1997); upper l imb (Sadoyama et al . , 1983, De Luca et al . ,
1986, Lowery et a l . , 2002, Mori tani et a l . , 1988) and back (El fv ing et
a l . , , Koumantakis et a l . , 2001a, Ng et al . , 2002, Mannion et a l
e. The present s tudy used both fast and slow speed of
ontract ion which enables examinat ion of the inf luence of
2000
1998, Nargol et a l . , 1999). This decrease in EMG median frequency
in the fat igued muscle may be explained by the progressive slowing
of conduct ion veloc i ty which in turn may prolong the f ibre act ion
potent ia l wave form (Lowery et al . , 2002, Lindstrom et al . , 1995).
Slowing of conduct ion veloci ty may occur as a funct ion of the
accumulat ion of some metabol i tes such as lact ic acid dur ing
fat iguing exercise (Bigland-Ritchie et a l , 1981).
The ear l ier studies which examined the relat ionship between fat igue
and EMG median frequency used ei ther isometr ic contract ions or
s low speed (up to 120° per second) isokinet ic exercise (Arendt-
Nielsen et al . , 1988, Lowery et a l . , 2002, Sadoyama et al . , 1981,
Linssen et a l . , 1991b, Masuda et a l . , 1999, Broman et a l . , 1985,
Warren et al . , 2000, Gerdle et a l . , 2000, Linnamo et al . , 2000) to
induce fat igu
c
contract ion speed on EMG median f requency.
119
In the present study, the level of fat igue was based on indiv idual
decrements in torque and was conf i rmed by the recovery in strength.
Pr ior to the in i t iat ion of the main invest igat ion, a pi lot study was
conducted to conf i rm that a 90-second isokinet ic exercise regime
was suff ic ient to cause measurable fat igue in the designated
muscles. Simi lar ly, the pi lot project conf i rmed that 7 minutes was an
adequate per iod for recovery of muscle strength, i r respect ive of the
speeds used, or the number of repet i t ions performed.
The f inding of an associat ion between muscle fat igue and decrease
in EMG median f requency is consistent wi th ear l ier research
(Sadoyama et al . , 1983, McHugh et a l . , 2001, Masuda et al . , 1999,
Stulen and De Luca, 1981, Broman et al . , 1985). In the present
study, the extent of the decrease in knee extension torque when the
muscle was fat igued was not inf luenced by the speed of contract ion
of the muscle. Resul ts show there was no signi f icant di f ference in
the percentage of the extension torque drop af ter the slow or fast
fat iguing exercises, indicat ing that the two vast i lateral is muscles
were at the same level of fat igue i r respect ive of the speed of
exercise. I t fo l lows that the degree of fat igue of a muscle should be
ref lected in the magnitude of decrease in EMG median f requency.
As such, i t might be ant ic ipated that two muscles of equal degree of
fat igue resul ts in the same magnitude of decrease in EMG median
frequency.
In th is study, resul ts shows that the magnitude of the EMG median
frequency of the vastus lateral is , expressed as a percentage,
measured af ter s low speed fat iguing exercise decreased signi f icant ly
120
greater than af ter the fast speed exercise to fat igue. In the
determinat ion of the EMG median frequency, i t was expected that
between subjects var iat ions would occur. For th is reason a
normal ised percentage of the b i lateral d i f ference of the
measurement of each indiv idual subject was considered a more
appropr iate and accurate parameter to be used in the study than the
absolute values of EMG median frequency. I t is suggested (Warren
et al . , 2000) that the decrease in EMG median frequency af ter s low
speed fat iguing exercise may be interpreted as an increased
act ivat ion of s low motor uni ts ( type I) and a decreased act ivat ion of
st uni ts ( type I I ) . Resul ts in the present study show that the EMG
ci ty due to fat igue.
fa
median f requency decreases more af ter s low speed exercise than
af ter fast speed exercise which can be interpreted as greater
act ivat ion of s low twi tch f ibres ( type I) in response to the slower
speed of fat iguing exercise. Simi lar ly, the more modest percentage
decrease in the EMG median frequency of the vastus lateral is af ter
fast speed exercise suggests that fast twi tch f ibres ( type I I ) were
act ivated af ter fast speed exercise (Bi lodeau et al . , 2002). I t has
also been suggested (Sadoyama et al . , 1983) that s low twi tch f ibres
may be more act ivated in response to s low fat iguing exercise as a
funct ion of the recrui tment of motor uni ts wi th a s lower conduct ion
veloci ty (Petrofsky and Lind, 1980) and/or the decrui tment of the
act ive motor uni ts wi th a faster conduct ion velo
Resul ts of the present study show that the test used to represent
s low speed exercises (30° per second) is suggested to act ivate type
I muscle f ibres and 300° per second represent ing fast speed
exercise act ivates type I I f ibres. However, i t is st i l l not possible to
121
draw any conclusions concerning the precise speed required to
isolate the slow and fast speeds of exercise which target the type I
and type I I muscle f ibres respect ively. These two extreme points on
the speed cont inuum were selected to increase the possibi l i ty o f
demonstrat ing a d i f ference in EMG median frequency. Cl in ical ly,
isokinet ic exercises at these speeds are rarely used for
al of the hydrogen ions and lact ic acid (Jones 1981). The
rate of recovery is dependent upon the capi l lary densi ty of the
rehabi l i ta t ion purposes. More commonly used in speeds, that is
between 60° to 240° per second should be used in future research to
fur ther substant iate the relat ionship between EMG median frequency
of a muscle and the speed of muscle contract ion.
I r respect ive of the speed, a per iod of 7 minutes was suff ic ient to
al low ful l recovery of the EMG median f requency fol lowing the
fat iguing exercise. This f inding was consistent wi th ear l ier resul ts
involving the quadr iceps of 20 male subjects which showed that the
EMG median frequency of the quadr iceps returned to the pre-fat igue
value less than 10 minutes fol lowing the exercise (Cornwal l et a l . ,
1994). Theoret ical ly, the physiological mechanisms related to the
recovery process can be at t r ibuted (Cornwal l et a l . , 1994) as the
restorat ion of b lood f low to the muscle (Stul l and Clarke, 1971) and
the remov
contract ing muscle (Tesch and Wright, 1983).
Resul ts of the present study show the change of EMG median
frequency of a muscle immediately af ter the 90 seconds of isokinet ic
exercise at a speci f ic speed which according to ear l ier research
(McNair and Wood, 1993, Kupa et al . , 1995), may infer the
122
immediate response to the f ibre composi t ion of the muscle. I t can
be assumed that isokinet ic exercises performed at a s low speed (30°
to 60° per second) act ivate type I muscle f ibres and isokinet ic
exercises performed at fast speed (240° to 300° per second) act ivate
type I I muscle f ibres.
To achieve a s igni f icant ef fect f rom a t raining program, the training
intensi ty which is part ly determined by the number of repet i t ions,
must be appropr iate (Grimby, 1985). The higher the intensi ty, the
reater is the increase in s trength (McDonagh and Davies, 1984).
Inc
size r
wel l d
that,
streng
achiev
muscl
progra
with d degree of
atrophy in a part icular muscle and the populat ion of f ibre types
inv
An ex
appl ie
I t is k m ACL injury would develop a
speci f ic type of muscle atrophy to the knee muscle (McNair and
Wo
1970)
g
reases in muscle cross-sect ional area or indiv idual muscle f ibre
ef lect ing muscle strengthening and hypert rophy are typical and
ocumented (Hakkinen and Komi, 1983). I t can be assumed
with appropr iate number of repet i t ions at a given speed, a
thening ef fect of a part icular muscle f ibre type may be
ed. The idea of using a part icu lar speed to act ivate a speci f ic
e f ibre type is not current ly used in ACL rehabi l i tat ion
ms. As such, knowledge of EMG median frequency produced
i f ferent speeds may be useful in determining the
olved.
ample of how the resul ts of the present study can be cl in ical ly
d is found in the rehabi l i tat ion of ACL in jury or reconstruct ion.
nown that pat ients suf fer ing fro
od, 1993, Nakamura et a l . , 1986, Gerber et a l . , 1985, Edstrom,
. The ul t imate aim of th is l ine of research is to provide
123
inform
protoc
study
of exe
ACL
target
isokin
In summary
There are no signi f icant gender or bi lateral d i f ferences in the
EMG median frequency of the vastus lateral is of a group of 34
heal thy subjects. There was a s igni f icant decrease in the
EMG median frequency of the vastus lateral is in response to
both fast and slow speeds of fat iguing exercise. The
percentage drop in the EMG median f requency of the vastus
lateral is was higher af ter s low speed than af ter the fast speed
exercise in contrast to the extension torque which decreased
uni formly in both fast and slow speed condi t ions.
No di f ference was found in the percentage recovery in the
EMG median f requency of the vastus lateral is af ter s low or fast
speed fat iguing exercises. This f inding indicates that the EMG
median f requency returned to the pre-exercise level af ter the
recovery per iod of 7 minutes.
Assuming from ear l ier research, a relat ionship between the
changes in EMG median frequency and the muscle f ibre type
at ion which may assist in designing an isokinet ic exercise
ol for pat ients wi th ACL reconstruct ion. The f indings of th is
provide informat ion which may be of value in the development
rc ise protocols designed to minimize muscle atrophy fol lowing
reconstruct ion. When developed this protocol would aim to
speci f ic muscle f ibre types using a selected speed of
et ic exercise.
124
composi t ion (McNa a et al . , 1995), the
resul ts suggests that s low twi tch f ibres ( type I ) in the vastus
lateral is are more act ivated with s low speed (30° per second)
exercis ted with fast
econd) exercise. Consequen e
use this knowledge in the rehabi l i tat ion of pat ients
suf fer ing f rom ACL injury or reconstruct ion in the prevent ion or
i r and Wood, 1993, Kup
e and fast twi tch f ibres ( type I I ) are act iva
speed (300° per s t ly, i t may b
possible to
restorat ion of a speci f ic type of muscle f ibre atrophy.
125
Chapter Five
subsequent to A
EMG median frequency changes in the knee muscles
CL reconstruction
I
r ies are common, wi th data showing their incidence to be
approximately 50 per 100,000 each year in the general populat ion in
the USA (Wilk, 1997) and much higher in sport (Hurwitz et a l . , 1997,
Nordslet ten et a l . , 1997, Wi lk, 1997). For example, in the Uni ted
States, more than 250,000 athletes are diagnosed with ACL in jur ies
each year (Clasby and Young, 1997) and the most common sports in
which they occur are ski ing, footbal l , netbal l , gymnast ics, basketbal l ,
and soccer (Wi lk, 1997). I t has been est imated that ski ing alone
accounts for more than 100,000 ACL in jur ies each year (Hurwi tz et
a l . , 1997). Complete rupture of th is l igament was reported to
const i tute 15% of a l l a lp ine ski ing in jur ies (Nordslet ten et a l . , 1997)
and the incidence of ACL disrupt ion was 4.2 and 4.4 per 100,000
skier days in men and women respect ively (Viola et a l . , 1999). In
the past, ACL in jury was regarded as " the beginning of the end for
the knee" (Giove et al . , 1983, Torg et a l . , 1976) and was responsible
for shortening the careers of many ski l led ath letes (Wi lk, 1997) .
Today, due to an improved understanding of ACL in jur ies, complete
recovery and return to fu l l sports part ic ipat ion is expected in most
cases.
5.1 ntroduction
ACL inju
126
Although there are di f fer ing opinions wi th respect to the opt imum
rehabi l i tat ion program, there is consensus in the l i terature wi th
respect to the aims of an ef fect ive rehabi l i tat ion program fol lowing
ACL injury. These aims include:
• control l ing the signs and symptoms;
• prevent ing compl icat ions, especial ly muscle atrophy, fo l lowing
ACL in jury;
• maintaining stabi l i ty of the knee;
• restor ing and maintaining pre- in jury levels of muscle st rength;
and
• helping pat ients wi th an ACL def ic iency to return to thei r pre-
in jury level of sports part ic ipat ion.
ough research cont inues to provide cl in ic ians and therapists wi th
d valuable informat ion on improving management of an ACL
there is s
Al th
new an
injury, ome controversy re lated to the most appropr iate
t reatment and the management of ACL injury. Topics of debates
include
Mc
Da
approach
how
Shel
more recent l
(Sh
d the relat ive meri ts of a surgical (Giove et al . , 1983,
Daniel and Dameron, 1980, Nicholas et a l . , 1976, McDaniel and
meron, 1983, Sandberg and Balkfors, 1988) or non-surgical
(Clancy et al . , 1981, Fet to and Marshal l , 1980); when and
the operat ion should be performed (Noyes et a l . , 1984,
bourne et al . , 1995, Howe et al . , 1991, Yasuda et al . , 1989); and
y the ef f icacy of post-operat ive rehabi l i tat ion programs
elbourne and Nitz, 1990, Melone and Garret t , 1992).
127
In recent years, studies have shown that atrophy of muscles
surrounding the knee occurred subsequent to ACL in jury or
recon on resul t ing f rom instabi l i ty of the
he discovery that the EMG median frequency can be used as a non-
infer muscle f ibre composi t ion (Kupa et al . , 1995,
cHugh et al . , 2001) provides the opportuni ty to detect speci f ic
to di f ferent t ra in ing protocols. Current rehabi l i tat ion
rograms (Shelbourne et al . , 1992, De Carlo et a l . , 1992) focus on
the
are no at ion protocols
wh
struct ion due to the adaptat i
knee jo int . This muscle f ibre loss is f ibre type dependent (Edstrom,
1970, Baugher et a l . , 1984, Nakamura et al . , 1986, Gerber et a l . ,
1985, McNair and Wood, 1993), however, research f indings are
inconsistent regarding the type of muscle f ibre that atrophies.
Edstrom (1970) and Nakamura and col leagues (1986) found atrophy
of type I f ibres fo l lowing ACL in jury, whereas other researchers
(Baugher et a l . , 1984, McNair and Wood, 1993) have found a
reduct ion in the cross-sect ional area of type I I f ibres. Gerber and
col leagues (1985) found equal proport ions of both type I and type I I
muscle f ibre atrophy. There is l i t t le informat ion indicat ing the t ime
required to develop such muscle atrophy and the nature of the intra-
muscular changes. The degree of at rophy involved fol lowing ACL
in jury is unclear.
T
invasive method to
M
muscular f ibre atrophy ear l ier . The technique al lows rout ine non-
invasive evaluat ion of the muscular adaptat ion which may occur in
response
p
restorat ion of post ACL reconstruct ion muscle f ibre atrophy but
t f ibre type speci f ic . Incorporat ion of rehabi l i t
ich target speci f ic f ibre types may be important to compensate for
128
any l
recon
The m was to ident i fy changes in the EMG
me
poten
the kn 2 months fol lowing
AC
minim
month
recove ,
cNair and Wood, 1993, Kupa et al . , 1995), EMG median frequency
ight be used to infer the proport ion of f ibre type in the muscle.
a imed to determine the muscle strength and
funct ional capaci ty of the reconstructed knee as a measure of the
oss or at rophy of speci f ic f ibres post ACL in jury and
struct ion.
a in purpose of th is s tudy
dian frequency fol lowing ACL reconstruct ion and to evaluate the
t ia l b i lateral d i f ference in EMG median frequency measures of
ee muscles in a group of subjects 6 to 1
L reconstruct ion. A 6-month post-operat ive per iod is considered
um by some surgeons to begin isokinet ic test ing and 12
s post-operat ively is regarded as an ear ly s tage of fu l l
ry. By reference to previous research (Wrest ing et a l . , 1987
M
m
This study also
degree of post-operat ive recovery and to invest igate the re lat ionship
between these measures and EMG median f requency.
5.2 Methodology
Al though i t was in i t ia l ly planned to use muscle biopsies there were
compel l ing reasons not to use the procedure for the fo l lowing
reasons:
• Subject recrui tment was extremely di f f icul t and this would have
been more l imi t ing had biopsies been required.
• This was part icu lar ly the case when at tempt ing to engage
subjects who had undergone surgical procedures to the knee.
129
In addi t ion, for th is c l in ical cohort , the surgeon involved would
only agree to perform one biopsy dur ing the course of the
study, thus l imi t ing the value of th is measure from a
prospect ive perspect ive.
• The biopsy could only be taken for th is group dur ing surgery.
This made the t iming of the evaluat ion di f f icul t and somewhat
unrelated to the main aims of the project .
• The predict ive value of EMG median f requency in determining
muscle f ibre type had been previously establ ished in the
l i terature using muscle biopsies. As such, fur ther val idat ion
was not considered necessary for the purposes of th is s tudy.
5.2.1 Subjects
Twelve male pat ients were recrui ted for th is study from the
Holy Spir i t Hospi ta l in Br isbane, and
the Br isbane Al l Sports Physiotherapy Centre. Al l subjects had
suffered a complete isolated and uni lateral c l in ical ly conf i rmed ACL
tear and received an ACL reconstruct ion using a semitendinosus and
graci l is graf t . Al l subjects except one were operated on by the same
orthopaedic surgeon and at the t ime of test ing, they ranged in age
from 15 to 40 years wi th an average of 23.1 (± 6.7) years. Time
elapsed s ince the operat ion var ied from 7 months, (minimum t ime
the orthopaedic surgeon would approve isokinet ic test ing), to 12
months, wi th an average of 8.92 (± 1.9) months. Pat ients were
required to commit to a prolonged course of post-operat ive
rehabi l i ta t ion for hal f an hour per day for 6 months. (The out l ine of
Orthopaedic Department of the
130
the rehabi l i tat ion program is shown in Appendix F). No special
rehabi l i tat ion protocols or act iv i t ies which may have targeted a
speci f ic muscle f ibre type were reported since their operat ion by any
of the subjects. Of the 12 subjects, 7 had reconstruct ion to the r ight
knee and 5 to the lef t knee. Pat ients wi th other associated knee
surgery, such as meniscectomy or those with a record of previous
knee surgery were not included in the study. Those who met the
inclusion cr i ter ia (see Appendix C) were informed of the study by
their c l in ic ian and were invi ted to part ic ipate by contact ing the
invest igator. Subjects were informed of the nature of the project
5.2
Subjects were tested in the Physiology Laboratory of the School of
Human Movement Studies and the pre-evaluat ion procedures
invol
administ rat ion of the PAR-Q checkl ist (see Appendix F) and the
general warm-up sessions were as descr ibed in Chapter Three of
th is research project . In addi t ion, the funct ional capaci ty of the knee
for each subject was evaluated by appl icat ion of the Cincinnat i
Rat ing Scale (Noyes et al . , 1984) (Appendix E). The procedure used
a quest ionnaire speci f ical ly designed to evaluate the funct ional
capaci ty of the ACL def ic ient knee. The instrument included
through a subject informat ion package which was included as a part
of the eth ical approval process. This approval was granted by the
QUT and the Holy Spir i t Hospi ta l Human Ethics Commit tee and the
study was conducted in accordance with NH&MRC guidel ines for
Human Experimentat ion.
.2 Experimental procedure
ving screening of subjects for musculoskeleta l d isorder,
131
quest io
perform
related
points)
act iv i t i
(10 po
points
points
normal
Fol lowing th for EMG
recording and analysis using the procedure out l ined in the ear l ier
sect ions of
p laced on
semitendino
EMG eva
The EMG
frequency
determine
descr ibed
with the
the Kin-C
• Evalu
frequ
ns related to c l in ical s igns and symptoms and the abi l i ty to
funct ional act iv i t ies. The cl in ical component includes i tems
to pain (20 points) , swel l ing (10 points) and giv ing-way (20
. The component related to the abi l i ty to perform funct ional
es includes overal l act iv i ty level (20 points) , walk ing abi l i ty
in ts) , c l imbing stairs (10 points) and running and jumping (5
each). Taking pain as an example, no pain, wi l l score 20
and extreme pain wi l l be given a score of zero points. A
knee should score 100 points.
e funct ional evaluat ion, subjects were prepared
this paper. Fol lowing skin preparat ion, e lectrodes were
the bel l ies of vastus lateral is , vastus medial is and
sus as in the previous exper iment (Figures 3.1 to 3.5).
luation and Isokinetic testing
and the isokinet ic test ing equipment, the EMG median
acquis i t ion procedure and the EMG signal processing to
EMG spectral parameter in th is study were the same as
in Chapter Three. EMG was recorded simultaneously
measurement of torque and angular displacement using
om isokinet ic dynamometer.
ation of bi lateral discrepancy of EMG median
ency
132
The
detec i f ied (Qantec) pr ior to
downloading to the AmLab Data Acquis i t ion System. The
ta represent ing muscles of the
reconstructed and contralateral knees was compared and any
pectrum (r ight shi f t ) .
revious research (McNair and Wood, 1993) suggests
median frequency shi f t of each subject was correlated
EMG signals f rom the muscles of both l imbs were
ted by surface electrodes and ampl
EMG median frequency da
bi lateral d iscrepancies ident i f ied and presented as
percentages. This data was compared to the mean values for
the corresponding muscles of the non-dominant l imb of the
normal male subjects in Study One (n=33).
The bilateral shift of EMG median frequency
Using the contralateral l imb of each subject as the
control , the di f ference in EMG median f requency
discrepancy of the reconstructed l imb in relat ion to the
control was regarded as the bi lateral EMG median
frequency shi f t for each muscle. The presence of a
higher EMG median frequency in the ACL reconstructed
l imb in relat ion to the contralateral l imb was
demonstrated by a posi t ive di f ference whi le a lower EMG
median frequency was indicated by a negat ive
di f ference. A posi t ive di f ference represents a shi f t to
the higher end of the f requency s
P
that a r ight shi f t is related to atrophy of type I f ibres
whi le a negat ive di f ference represents a shi f t to the lef t
and an atrophy of type I I f ibres. The bi lateral EMG
133
with the knee funct ional abi l i ty score, thei r age and
length of post-operat ive per iod.
•
ed
immediate ly by another 8-second maximum isometr ic
amstr ings at the posi t ion of 45° knee
f lexion as descr ibed in Chapter Three. Subjects complete an
c le was also
performed and expressed in percentages. The bi la teral
d iscrepancy was correlated with the bi lateral EMG median
Isometric strength testing
The preparat ion procedure and the posi t ioning of the knee in
the evaluat ion of muscle strength were simi lar to that
descr ibed in Chapter Three. In th is study, the contralatera l
leg is tested f i rst and an 8-second isometr ic contract ion of the
quadr iceps is in i t ia l ly performed. This is fo l low
contract ion of the h
extension-f lexion cycle and the cyc le was repeated four
t imes. Once test ing of the contralateral leg was completed,
the same procedure was repeated to the ACL reconstructed
l imb af ter a 5 minutes rest . Consistent verbal encouragement
was given throughout the whole per iod of test ing. The
maximum torque value of each set of knee extension and
knee f lexion was expressed in Newton-meters (Nm) and was
recorded for data analysis. The relat ive st rength of the two
muscle groups of the same leg was calculated as a rat io
(H:Q) and presented as a percentage.
A bi lateral strength comparison of each mus
134
f requency shi f t for each indiv idual muscle and the knee
funct ional abi l i ty score for each subject .
er analysis of results
the bi lateral
d iscre he EMG median frequency of the three muscles
and the
ACL compare the
n EMG median frequency and torque values between the
ACL
coef
func
post
f lexo
• Furth
In order to provide greater insight into the nature of the data
associated with the ACL repaired subjects, their resul ts were
further categor ised with respect to their funct ional score, the
percentage of the bi lateral torque discrepancy and the EMG
median frequency shi f t o f VM and VL in relat ion to MH.
5.2.3 Statistical analysis
One-way ANOVA wi th the Tukey Post-hoc test and mult ivar iate 2 x 3
mixed model of ANOVA was used for stat ist ical analysis. Paired t -
tests were used to determine di f ferences in
pancies of t
the torque values of the knee f lexors and knee extensors of
subjects. Independent t - tests were used to
di f ferences i
and the normal (Study One) subjects. Spearman’s correlat ion
f ic ients were used to evaluate any associat ion between the knee
t ional scores and age, EMG median frequency values, length of
-operat ive per iod and the torque of knee extensors and knee
rs. The level of s igni f icance was set at p<0.05.
135
5.3
5.3.1 The EMG median frequency
The median f requency of VL, MH and VM of the ACL
econstructed l imb and the corresponding muscles of the l imbs of the
contr
medi
is sh
comp
vastu
signi
reco
contr us
medial is of the ACL reconstructed was higher than that of the normal
i f icant (p=0.058).
ed l imb was lower than that for the contralateral
l imb. In contrast , the vastus medial is recorded higher mean
ure when this comparison was made. None
i f ferences reached signi f icance (p=0.16 to 0.367). The
Results
mean EMG
r
alateral l imb are shown in Table 5.1 and Figure 5.1. The EMG
an frequency for the normal subjects invest igated in Study One
own and wi l l be referred to as the control group and used for
arat ive purposes. The mean EMG median frequency of the
s lateral is (p=0.041) and media l hamstr ings (p=0.005) was
f icant ly higher in the contralateral l imbs of the ACL
nstructed subjects than in the corresponding muscles of the
ol group. Al though the mean EMG median frequency of vast
group, the di f ference was not s ign
Comparison of the bilateral discrepancy of EMG median
frequency of the ACL reconstructed subjects
As shown in Table 5.1 and Figure 5.1 the mean EMG median
frequency for the medial hamstr ings and vastus lateral is of the
ACL reconstruct
values for th is meas
of the d
ACL reconstruct ion group however, had a s igni f icant ly h igher
(p=0.0028 for the VL, 0.002 for the MH and 0.02 for the VM)
136
mean percentage of bi lateral d iscrepancy than that of the
normal group (Figure 5.2).
The EMG median frequency shift of the ACL reconstructed
s
nces in the
lues of the EMG median f requency of the muscles, high
5.3.
incinnat i rat ing scores for knee funct ion ranged from 60 to 98 out
of 1 .5 points ± 14.14 in ACL
recon cted subjects (Table 5.2). The scores indicate funct ional
rat in
class
et al .
5.3.3
Isom
ACL reconstructed and contralateral l imbs are presented in Table
ubjects
Although there were no signi f icant bi lateral d i f fere
mean va
var iabi l i ty was found in the data (Table 5.1), indicat ing that the
var iance in EMG median frequency of the muscles in the ACL
reconstructed l imb in relat ion to those of the contralateral l imb
was high. The absolute shi f t in EMG median frequency for the
three selected muscles of the ACL reconstructed l imb in
relat ion to the contralateral l imb are presented in Figure 5.4.
2 Knee functional capacity
C
00 points wi th a mean of 82
stru
gs ranging from “fai r” to “excel lent” wi th the average rat ing
i f ied as “good” according to the funct ional abi l i ty scale (Noyes
, 1984).
Isometric torque
et r ic strength values for the quadr iceps and hamstr ings of the
137
5.3 a
musc .04)
an that of the ACL reconstructed l imb. In contrast , no di f ferences
s igni f icant level (p=0.59). The relat ive strength of the
amstr ings was considered high when compared with the H:Q
alues of normal heal thy subjects that l ie wi th in the range of
50% to 70% of the quadr iceps strength (Kannus, 1994).
l strength discrepancy
The percentage bi la teral d iscrepancy of the isometr ic s trengths
of the quadr iceps and hamstr ings muscles for indiv idual ACL
reconstructed subjects is shown in Table 5.4. The percentage
bi lateral d iscrepancy of the quadr iceps isometr ic st rength
ranged f rom 0.11% to 11.52% and the hamstr ings from 0.55% to
39.35%. No signi f icant correlat ions were found between the
percentage bi la tera l d iscrepancy in isometr ic strength of the
nd (Figures 5A.3 to 5A.4). The mean hamstr ings strength of
les of the contralateral l imb was signi f icant ly higher (p=0
th
were found in the mean quadr iceps st rength between l imbs (p=0.28).
The knee f lexor and knee extensor strength ratio
The hamstr ings/quadr iceps strength rat ios (H:Q rat io)
expressed in percentages are presented in Table 5.3 and
Figures 5.3. The mean H:Q values for the ACL reconstructed
subjects (77.92%) appeared higher than that recorded for the
contralateral l imb (74.39%). However th is di f ference but did not
reach the
h
v
Bilatera
138
quadriceps and hamstr ings and the EMG median frequency shi f t
of the three muscles (Figures 5A.5 to 5A.8 in Appendix A).
5.3.4 Relationship between functional measures and shift in EMG
median frequency
No signi f icant relat ionships were found between EMG median
frequency and the knee funct ional score and torque for knee
extension (r=0.11) and f lexion (r=0.18) (p>0.05). Simi lar ly, the
associat ions between age (r=-0.4), t ime since operat ion (r=0.5), the
bi lateral d i f ferences in EMG median f requency of VL (r=-0.12), MH
(r=-0.31), and VM (r=-0.04) and knee funct ional score did not reac
ppendix A).
h
signi f icance (Figures 5A.9 to 5A.11 and Figures 5A.12 and 5A.13 in
A
139
0
20
40
60
80
z100
*VL *MH VMMuscles
EMG
MF
in H
120Normal
Contralateral
ACLR
F ig 5 .1 EMG MF in Hz o f the VL, MH and VM of non-domin ion l imb o f norma l sub jec ts , t he cont ra la te ra l and the reconst ruc ted l imbs o f the ACL sub jec ts *Denotes s ign i f i cant d i f fe rence (p<0.05)
0
5
10
15
20
25
30
35
40
VL MH VMMuscles
Perc
enta
ge %
Normal
ACL
F ig 5 .2 Percentage b i la tera l d i sc repancy in the EMG MF o f the VL, MH and VM of normal sub jec ts and ACL reconst ruc ted sub jec ts
140
0
10
20
40
50
0
0
100
B C D E F G H I J K LACL Reconstructed Subjects
H:Q
Rat
io in
%
90
60
7
8
30
ANormHQ ACLHQ
g 5 .3 Re la t i ve isomet r ic s t rength o f the hamst r ings and quadr iceps (H:Q ra t io )
f the cont ra la tera l l imb (NormHQ) and the recons t ruc ted l imbs (ACLHQ) o f the CLR sub jec ts
F ioA
-60 -40 -20 0 20 40 60
B D %
edian f hift inM requency s Hz
ig 5 .4 The EMG MF sh i f t o f the VM (b lue) , VL (ye l low) and MH (o range) o f the ACL recons t ruc ted l imb measured i somet r ica l l y and tak ing the cont ra la tera l l imb as a zero re fe rence po in t (n=12) .
F
141
Tab le 5 .1 Mean o f the EMG MF in Hz o f the VL, MH and VM of the cont ra la tera l and the ACL reconst ruc ted l imbs.
VL MH VM
Con ra-lateral ACL lateral
t Contra-ACL
Conlatera
tra-l AC L
Mean 71 65 87 79 67 75 (SD) 16 12 25 16 8 16
Tab le 5 .2 e knee f na es us in inc innat g Sys to f t he c ted su
PainSwel l in
g Giv in
Way vera lk ing S rs
Running
p in To
Me n o f thACL reconst ru
a unct iob jec ts .
l scor g the C i Rat in em
g O al l
Wta i
Jumg tal
Mean 16.0 8.8 15.8 9.2 4.0 8 816.0 8.8 3. 2.5 (SD) 3.0 1.6 5.8 2.9 1.6 0.9 14 1.6 0.7
(n=12
Tab le 5 .3 Me n o f the isome orq the knee tensors and e f lexorand the H:Q ra t ios o f the ACL reconst ruc ted sub jec ts .
)
a t r i c t ue o f ex kne s
Norm Ext ACL Ext Flex ACL Flex Norm H:Q Norm
ACL H:Q
Mean % 8.97 Nm 8.4 Nm 7.0 Nm* 6.3 Nm 77.92 % 74.39 (SD) 1.4 1.2 2.0 2.1 22 22
No rm = Co n t ra l a t
e r a l l im b , A CL= Rec on s t r uc te d l i mb *S ig n i f i c a nce Lev e l p= 0 .0 4
Tab le 5 .4 Mean o f the C inc innat i knee t iona l score tera l d isc rep y o f the EMG MF an % BD o f knee extens nd knee f le t rengths o f CL reconst ruc ted s b jec ts .
Cincin at i Score % MFBD
VL % MF BD % M F
VM
% BD Ext
Torque
BD x
rque
func , b i la ancd ion a x ion s the Aun
MH BD
%Fle
to
Mean 82.5 15.9 2 12.8 7.7 .3 2 0 . 11SD 14.2 9.7 12.40 11.9 8.4 11.3
Ex t=e x te ns io n , F l e x =F l e x i on
142
Table 5 .5 Mean va lues fo r age, pos t -opera t i ve dura t ion , EMG MF o f the med ia l
Score
Age (year)
Post-op per iod (Months)
Contralateral MH ACL VM
hamst r ings o f the cont ra la tera l l imb and the EMG MF o f the vas tus med ia l i s o f the ACL recons t ruc ted l imb when sub jec ts were grouped accord ing to the h igher and lower func t iona l sub-groups
60 25 9 96 77 64 23 8 96 110 68 36 7 96 65 70 25 7 87 84 73 25 9 128 84 LFG 67.0 26.8 8.0 100.6 84.0 90 30 7 56 73 92 15 9 51 60 92 16 9 110 83 9 26 114 75 94 15 9 67 73 95 26 12 55 46 98 15 8 83 64
Mean HFG 93.6 20.4 9.4 76.6 67.7
Mean
4 12
(Mean va lues in bo ld pr in t ) LFG=Lfunct iona l group
ow funct ional group HFG=High
Table 5 .6 Mean values for age when subjects were grouped accord ing to the larger and smal ler b i la tera l torque d i f fe rence in knee extension and knee f lex ion
Ext BD Flex BD Age 0.1 0.6 25 2.4 1.8 26 3.0 2.9 25 3.6 4.8 25 3.6 5.9 15 4.7 6.5 15 4.8 7.0 15 6.0 9.6 26
Mean Smaller BD group 3.5 4.9 21.5
10.3 13.6 30 10.4 21.2 16 11.5 22.2 36 31.9 39.4 23
Mean Larger BD group 16.0 24.1 26.3 (Mean va lues in bo ld pr in t )
143
Tab le 5 .7 Mean va lues fo r EMG MF sh
b je were g rouped accord ing to the di f t i n Hz o f the med ia l hamst r ings when
su c ts i rec t ion o f EMG MF sh i f t o f the vas tus la t ra l i s and vas tus media l i s
e
VL MH VM MH
-17 33 -43 19
-7 19 -25 34
-6 9 -11 -17
-4 57 -5 -23
Mean SG -8 20 -4 57
5 0 -4 10
9 -22 -1 -22
13 -23 Mean SG -12 12
16 16 2 -20
19 -20 7 9
-6 -17 -14 16
8 10 -1 33
39 34 10 0
an SG 16 -1 Mean SG 6 -4 Me
Mea n S G =M e an v a lu es o f t he su bg ro up
144
5.4 Discussion and summary
Study One of th is project was designed to conf i rm and suggest a
rel iable protocol to be used in the determinat ion of EMG median
frequency for later phase of the project . A c l in ical s i tuat ion which
involves a speci f ic type of muscle f ibre and requires the
determinat ion of the EMG median frequency is the atrophic changes
fol lowing ACL in jury or reconstruct ion. As ment ioned previously in
the Introduct ion sect ion of th is Chapter, atrophic changes which
occur fo l lowing ACL reconstruct ion are f ibre type dependent, but th is
dependence did not occur in other major knee in jur ies such as
meniscectomy (Nakamura et a l . , 1984). For th is reason, ACL
reconstructed pat ients were selected in th is project .
This invest igat ion used the procedures establ ished in the ear l ier
sect ions of the paper to rel iably evaluate the EMG median frequency
in subjects who had undergone ACL reconstruct ion. I t is wel l
recognised that knee in jury is accompanied by atrophy of the
surrounding musculature and possible changes in the composi t ion of
muscle. This may include al ternat ion in the proport ion of the s low
twi tch and fast twi tch muscle f ibres, a l though there is l i t t le evidence
to substant iate th is hypothesis. Such knowledge of the potent ia l
a l ternat ion in muscle f ibre type fol lowing in jury has important
impl icat ions for the design of appropr iate rehabi l i tat ion programs.
By reference to previous research (Wrest ing et a l . , 1987, McNair and
Wood, 1993, Kupa et al . , 1995), i t is suggested that EMG median
frequency may be used to infer the proport ion of f ibre type in the
145
muscle. An addi t ional a im of the study was to use the measure of
MG median frequency to indirect ly predict any potent ia l b i lateral
d i f fe
mont t ion. The muscle st rength and
nct ional capaci ty of the reconstructed knee were determined as a
meas
inves
medi
This
subje
di f f ic
incre
meas
exten
addi t
analy
EMG
The
insig
comp
E
rence in f ibre type composi t ion in a group of subjects 6 to 12
hs fol lowing ACL reconstruc
fu
ure of the degree of postoperat ive recovery and were used to
t igate the relat ionship between these measures and EMG
an frequency.
project intended to study a larger number of ACL reconstructed
cts. However, the recrui tment process was unexpectedly
ul t and lengthy. Therefore, remedial measures were taken to
ase the subject number to a minimum level (n=12). These
ures included a s l ight modif icat ion of the inclusion cr i ter ia and
sion of the recrui tment t ime for subject of over (24 months.) In
ion, the resul ts of the study were further and more cr i t ical ly
sed by subdiv iding them according to the funct ional scores,
median frequency shi f t and percentage bi lateral d iscrepancy.
purpose of th is fur ther analysis was intended to provide greater
ht in to indiv idual subject informat ion and ident i f icat ion and
ar ison of indiv idual d i f ferences.
146
5.4.1
he corresponding muscles of the r ight legs of the normal
ts should not be considered as the
reference of normal i ty and may be an inappropr iate control wi th
EMG median frequency
The comparison between the ACL reconstructed subjects
and subjects of Study One
Consistent wi th previous research (Lindstrom et al . , 1995), the
resul ts of Study One on 33 normal male subjects showed no
bi lateral d iscrepancy in the EMG median frequency of the
muscles around the knee. I t can be concluded that under
normal c i rcumstances, the contralateral l imb can act as a
control in measurements when determining EMG median
frequency. The resul t of th is exper iment indicates that the
mean EMG median frequency of the vastus lateral is and
semitendinosus of the contralateral l imb was signi f icant ly higher
in the ACL reconstructed subjects than in normal subjects of
s imi lar age. The f inding is consistent wi th ear l ier research (van
Lent et a l . , 1994) which found signi f icant di f ferences in the
EMG median frequency of the quadr iceps and hamstr ings of the
contralateral legs of ACL def ic ient subjects when compared to
t
controls. This suggests that the contralateral l imb of the ACL
reconstructed subjec
respect to comparison with the ACL reconstructed l imb. This
f inding leads to the assumption that compensatory muscular
adaptat ion fol lowing ACL in jury or reconstruct ion may have
occurred in both l imbs. This is supported by research which
indicates that ACL rupture af fects the total gai t pat tern (Van
147
Lent et a l . , 1994) and consequent ly induces changes in the
muscle act iv i ty patterns of both the in jured and uninjured legs.
I t is possible that the adaptat ion in the muscles fo l lowing ACL
in jury or reconstruct ion may di f fer in the in jured and the
uninjured l imbs. Adaptat ion of the muscles of the ACL in jured
leg occurs to accommodate the anter ior laxi ty of the knee which
is known as the “quadr iceps avoidance” gai t (Berchuck et a l . ,
1990, Devi ta et a l . , 1997). Adaptat ion of the contralateral l imb
occurs to accommodate changes in the whole gai t pat tern
fo l lowing ACL injury or reconstruct ion (Van Lent et a l . , 1994)
and possibly as a compensatory mechanism to reduce the load
on the ACL reconstructed leg. Unfortunately, the cross-
sect ional design of the present study precludes the opportuni ty
to ident i fy the actual progressive changes that have occurred
fol lowing the ACL reconstruct ion. Longi tudinal analysis ,
preferably progressing f rom the ear l iest post-operat ive per iod to
several months post operat ively, would al low detect ion of any
ear ly funct ional changes, the progressive response in the EMG
median frequency and possible changes in muscle composi t ion.
The use of the contralateral l imb as a control to the ACL
reconstructed l imb
sing the contralateral l imb as the normal control in the
s as a point of reference when
ning the bi lateral shi f t in th is measure of muscles of the
in jured l imb. The bi lateral EMG median frequency shi f t is an
U
determinat ion of EMG median frequency is relevant in many
EMG studies because i t serve
determi
148
absolute value in hertz of one l imb in relat ion to the
contralateral l imb of the same subject using the same method of
EMG evaluat ion (McHugh et al . , 2001, Far ina et a l . , 2001). As
stated ear l ier , wi th reference to the contralateral l imb, a shi f t to
the lower end of the frequency spectrum produces a negat ive
f igure. This denotes a decrease in muscle conduct iv i ty and has
been suggested to be indicat ive of type I I muscle f ibre atrophy
(McNair and Wood,1993). The case is reversed with a shi f t to
the higher end of the frequency spectrum yielding a posi t ive
f igure. When the EMG median frequency of the contralateral
imb does not fo l low a normal pattern, a mis leading shi f t in th is
l
measure may occur making any predict ion of speci f ic muscle
f ibre atrophy erroneous. Al though logist ical and c l in ical
problems negated the opportuni ty for longi tudinal analysis in
th is study, ideal ly i t would be advantageous to ident i fy changes
in EMG median frequency both before and af ter the
reconstruct ion us ing the involved l imb. Intersession
comparisons of EMG median frequency shi f t in muscles of the
same l imb are also l imi ted by the high var iabi l i ty resul t ing f rom
exper imental errors (Davis et a l . , 1998). The detect ion of the
bi lateral asymmetry in EMG median frequency is st i l l important
in rehabi l i tat ion s ince the discrepancy is indicat ive of the
amount of compensatory act iv i ty of the contralateral l imb.
Bilateral EMG median frequency difference and the shift of
ACL reconstruction subjects
149
The bi lateral d i f ference in EMG median frequency was 17% in
the vastus lateral is and 17% in the vastus medial is muscles.
This f inding is s imi lar to the resul ts of an ear l ier study (McHugh
et al . , 2001) of ACL bone pate l lar- tendon bone ACL
reconstruct ion subjects studied 5 weeks post-operat ively. The
bi lateral d iscrepancy was 16% in both vastus lateral is and
vastus medial is despi te di f ferences in operat ive procedures and
the length of the post-operat ive per iods. This indicates that the
adapt ive changes in muscle are l ikely to occur very quickly af ter
in jury.
The shi f t in the EMG median frequency found in the present
tudy var ied among the three muscles of the ACL reconstructed
,
993). The reason for the inconsistency between this and the
s
subjects (Fig 5.4). This suggests speci f ic i ty in muscle
adaptat ion fol lowing in jury and supports ear l ier research which
found from muscle biopsies fol lowing ACL in jury that atrophy in
both type I and type I I f ibres may occur (Gerber et a l . , 1985).
In contrast , when using EMG median f requency as a predictor
of muscle composi t ion, McNair and Wood, (1993) found a
decrease in the mean EMG median frequency in the vastus
lateral is of the ACL in jured l imbs in relat ion to the contralateral
l imbs. This decrease was interpreted by the authors as an
atrophy of type I I ( fast twi tch) muscle f ibres (McNair and Wood
1
present study is mult i factor ia l and may relate to di f ferences in
the approach to management of the in jury, the length of the
post-operat ive per iod and the procedure used to determine
EMG median frequency. For example, a l l subjects recrui ted in
150
the present study received ACL reconstruct ion, in contrast to
the study of McNair and Wood’s (1993) in which subjects were
non-operat ively t reated. This di f ference in the mode of
intervent ion would most l ikely have a di f ferent ia l ef fect on the
adaptat ion occurr ing in the muscles of the knee. ACL
reconstruct ions have been shown to reduce knee antero-
poster ior laxi ty (Shaieb et al . , 2002, Woo et al . , 1997, Fu et al . ,
2000, Noyes and Barber-West in, 1997, Anderson et a l . , 1994,
Hess et a l . , 2002) and a recent study (Shaieb et a l . , 2002)
ound signi f icant decreases in knee jo int laxi ty af ter
y of type I I f ibres may be involved (Grimby et al . , 1980).
a luat ion of knee funct ion
fol lowing ACL reconstruct ion relates to the procedures used to
f
semitendinosus and graci l is graf t ACL reconstruct ion and 2
years fo l lowing the reconstruct ion.
The length of the post-operat ive per iod pr ior to the evaluat ion
of the knee funct ion is also a factor in the var iabi l i ty in the
resul ts of c l in ical s tudies. In the present study, the mean post
ACL in jury t ime was 9 months in contrast to 20 months in the
study of McNair and Wood (1993). Atrophy of speci f ic muscle
f ibre populat ions has been shown to vary according to the
length of the post-operat ive per iod (Kannus et a l . , 1987). In the
immediate post-operat ive per iod, atrophy in type I f ibres is
predominant in contrast to later s tages in the per iod when
atroph
Another source of var iabi l i ty in the ev
determine EMG median f requency. In th is invest igat ion, an 8-
second isometr ic contract ion was used to produce the EMG
151
signals in contrast to the ear l ier research (McNair and Wood,
1993) which used isokinet ic contract ions at a speed of 180° per
second. The f indings presented in Chapter Three ident i fy
s igni f icant d i f ferences in the rel iabi l i ty of the EMG median
frequency determined dur ing isometr ic and isokinet ic
contract ions. The constant muscle length dur ing isometr ic
contract ions was shown to increase the rel iabi l i ty of the EMG
median frequency (McHugh et al . , 2002b, Potvin, 1997, Kupa et
al . , 1995).
Associat ions were observed in the three muscles when 12
subjects were grouped according to the di rect ion of EMG
ht shi f t in vastus
lateral is were grouped together, a lef t shi f t in medial hamstr ings
The Cincinnat i funct ional abi l i ty scores for the subjects in th is study
are general ly higher than those reported ear l ier (Li et a l . , 1996,
median frequency shi f ts (Table 5.7). When subjects wi th a lef t
shi f t (negat ive) in vastus lateral is were grouped together, a
r ight shi f t (posi t ive) in the medial hamstr ings was observed in
th is group. Simi lar ly, when subjects wi th a r ig
was found. The same pattern of associat ion was observed in
the relat ionship of vastus medial is and medial hamstr ings.
Al though this associat ion did not reach a s igni f icant level , a
tendency of a di f ference between knee extensor and knee f lexor
muscles occurred in the di rect ion of EMG median frequency
shi f t .
5.4.2 The knee functional abil i ty score
152
N
t
s
c
r
r e non-
operat i e approach. Simi lar benef i ts of the surgical approach have
b
e
a
S
L
s
1
on the basis of a s ingle isolated rupture of the ACL.
d “below average” groups. Five of the 12 subjects had
cores of “below average”, def ined as ranging f rom 60 to 73 points
nd 7 “above average”, ranging f rom 90 to 98 points. Al though the
o examine more
losely the inf luence of knee funct ional capaci ty on the EMG median
oyes and Barber-West in 1997). This may ref lect the di f ference in
he treatment regime and the nature of the in jury. For example,
ubjects in the ear l ier study (Li et a l . , 1996) were treated
onservat ively in contrast to the present study in which subjects
eceived an ACL reconstruct ion. Greater s tabi l i ty was shown in the
econstructed knee by comparison with the more conservat iv
v
een shown in other studies which have made comparisons of the
f f icacy of d i f ferent approaches to ACL in jury (O’Nei l l , 1996, Gi l lquis t
nd Odensten, 1988, Zar ins and Rowe, 1986, Fu et a l . , 2000,
helbourne et al . , 1995).
ower funct ional scores have also been found in studies involving
ubjects wi th mult ip le knee pathologies (Noyes and Barber-West in,
995) in contrast to those included in th is study who were selected
The average knee funct ional score of the ACL reconstructed subjects
was 82.5 out of 100 points. Subjects were div ided into “above
average” an
s
a
sample s ize was l imi ted an at tempt was made t
c
frequency score. The mean values for EMG median frequency, age
and post-operat ive durat ion of the two groups are presented in Table
5.5.
153
The “above average” group had a mean age of 20.4 (±5.2) years and
an average post-operat ive per iod of 8.0 (±1.0) months. The “below
average” group was older, 26.8 (±6.6) years and had a longer post-
operat ive per iod of 9.4 (±1.9) months. Predictably, th is suggests
that the younger ACL reconstructed subjects recovered their knee
funct ional capaci ty in a shorter per iod than the older group.
An observable h igher mean EMG median frequency was found in the
medial hamstr ings of the contralateral l imb in the below average
group as compared to that of the above average group. The EMG
median frequency of the above average group was s imi lar to that of
the corresponding muscle of the normal male subjects reported in
Study One (Chapter three). In the vastus medial is of the ACL
reconstructed l imb, the “above average” knee funct ional abi l i ty group
had a lower EMG median frequency than the “below average” group.
These observat ions suggest that a high EMG median frequency in
the contralateral hamstr ings or in the vastus medial is of ACL
reconstructed subjects may inf luence the knee funct ional abi l i ty or
v ice versa.
5.4.3 Isometric strength of the knee muscles
Al though no di f ferences were found between the isometr ic extension
strength of the muscles of the reconstructed and contralateral l imbs,
f lexor strength was higher in the lat ter . These bi la tera l def ic i ts in
knee f lexion and knee extension strength (not reaching stat is t ical
154
signi f icant) were lower than reported previously (Mit t lmeier et a l . ,
1999, McNair and Wood, 1993, McHugh et al . , 2002b, Snyder Mackler
et a l . , 1993). This may ref lect d i f ferences in the t reatment regime
and the operat ive procedure, the length of the post-operat ive per iod
and the mode of measurement. However, the funct ional outcome may
not be a funct ion of a s ingle factor but rather a combinat ion of one or
m
p
p
b
b
s
o
T
d the nature and degree of compl iance with the
rehabi l i tat ion program.
The average decrease in f lexion torque of the ACL reconstructed l imb
in th
(74.3 lateral l imb but th is
di f ference was not s igni f icant . This rat io was however higher than
that
isokin
Aaga
knee
with
far a
ideal
ore of these factors. For example, the length of the post-operat ive
er iod is expected to contr ibute to the recovery of s trength and
redictably the longer the post-operat ive per iod, the lower the
i lateral strength def ic i t . Previous resul ts have shown that the
i lateral s trength def ic i t (32%) was greater in 12-week post-operat ive
ubjects (Mit t lmeier et a l . , 1999) than those fol lowing a 6-month post-
perat ive per iod (13%) as might be expected (McHugh et a l . , 2002a) .
h is suggests that funct ional recovery improves with t ime but may
epend on
e present study resul ted in a lower mean H:Q strength rat io
9%) by comparison wi th that of the contra
of normal subjects which ranges from 50% to 70% measured
et ical ly at 60° per second (Li et a l . , 1996, Cost i l l e t a l . , 1976,
ard et a l . , 1997, Kannus, 1994). Previous work showed higher
funct ional scores wi th an increase in the H:Q rat io in pat ients
ACL in jury or reconstruct ion (Li et a l . , 1996). Theoret ical ly, as
s the bi la tera l symmetry of the quadr iceps is maintained, the
H:Q rat io for ACL reconstructed knees should be as high as
155
100%
Aaga
the H
frequ
study
Two
aver
sepa
aver
f lexio
large
age
have
(Tabl
5.4.4 Correlation
(Murray et a l . , 1984, Li et a l . , 1996, van Lent et a l . , 1994,
ard et a l . , 1997). There was no signi f icant correlat ion between
:Q rat io of the ACL reconstructed l imb and the EMG median
ency shi f ts of the muscles of VL, MH and VM in the present
.
b i lateral torque di f ference groups, the torque di f ference “below
age” group and the “above average” group, were studied
rately. The group showing a smal ler torque di f ference (below
age) involved younger subjects (mean age 22) in both knee
n and knee extension, in contrast wi th the group showing a
r torque di f ference (above average) wi th older subjects (mean
26). This suggests younger ACL reconstructed patents may
higher abi l i ty to regain strength symmetry than older ones
e 5.6).
.
Correlation between the bi lateral strength discrepancy and
bi lateral EMG median frequency shift
No relat ionship was found between the percentage bi lateral
d i f ferences in knee extensor and f lexor torque and the EMG
median frequency shi f ts of the three involved muscles. This
f inding di f fers f rom that of an ear l ier study (McHugh et al . ,
2001) which showed a s igni f icant relat ionship between the
bi lateral post operat ive knee extension strength def ic i t and the
EMG median f requency def ic i t of 42 ACL subjects wi th bone
156
patel lar- tendon bone graf t reconstruct ion 5 weeks ear l ier . Their
resul ts showed that the bi lateral post-operat ive knee extension
strength def ic i t was related to the EMG median frequency
def ic i t ( r=0.46, p<0.02). This contrast in f indings may ref lect
d i f ference in the post-operat ive per iod at which the EMG
median frequency was determined at 5 weeks in the ear l ier
study and 9 months post-operat ively in the present study. As
reported in a later study conducted by the same authors
(McHugh et al . , 2002a), def ic i ts were most profound
immediate ly fo l lowing the operat ion, wi th marked bi lateral
asymmetry in strength and the EMG median f requency. I t is
expected that asymmetry wi l l d iminish wi th t ime dur ing the
recovery process. The rates of recovery in s trength and in
EMG median f requency may be di f ferent. As a resul t , a higher
f requency at 5 weeks than at 9 months post-operat ively.
correlat ion is expected between strength and EMG median
In the present study, the pre-fat igue values of isometr ic torque
had no di rect ef fect on the shi f ts in EMG median frequency of
the muscles. This concurs wi th ear l ier f indings (Ng et a l . , 2002,
Dedering et a l . , 2000, Mannion et a l . , 1998, Bigland-Ritchie et
a l . , 1981) which showed that the EMG median f requency is
independent of the torque value of a muscle and decreases only
when the muscle is fat igued. This f inding part ly explains the
higher EMG median frequency value of the medial hamstr ings
by comparison with the two vast i muscles (reported in Chapter
Three) which was reversed with respect to the torque value.
The independent character ist ic of the EMG median f requency
157
was supported by the f indings of other studies which showed no
signi f icant EMG median frequency di f ferences between
dominant and non-dominant rectus femoris and the vastus
lateral is (Lindstrom et al . , 1995), or the hand muscles of 35
normal subjects (De Luca et a l . , 1986). This character is t ic was
further supported by an ear l ier study (McHugh et al . , 2001)
which reported that the integrated EMG def ic i t was not related
to the def ic i t in EMG median frequency of a group of 42 ACL
subjects wi th bone patel lar- tendon bone reconstruct ion. The
measures
out the post-
perat ive per iod. A posi t ive relat ionship may have been found
same authors (McHugh et al . , 2001) fur ther explained that the
def ic i t in the EMG median frequency pr imari ly ref lected the
muscle f ibre composi t ion, whi le the def ic i t in the integrated
EMG pr imari ly ref lected muscle strength.
Correlation between knee functional abi l i ty and other
No signi f icant relat ionships were found between the Cinc innat i
knee funct ional scores and the percentage bi lateral d iscrepancy
in the EMG median frequency of the three muscles fol lowing a
9-month post-operat ive evaluat ion. As previously discussed,
th is does not imply a lack of associat ion between muscle
strength and knee funct ional abi l i ty through
o
at an ear l ier phase of the rehabi l i tat ion process. Access to
ACL pat ients for the present study was l imi ted by the treat ing
surgeons to a per iod not less than 6 months post-operat ively
and the post-operat ive per iod for indiv idual subjects ranged
from 7 months to 12 months. Al though no relat ionship was
158
shown between the EMG median f requency and the length of
the post-operat ive per iod, th is most l ike ly ref lects the relat ively
delayed stage of the rehabi l i ta t ion process at which the
evaluat ions occurred and the possibi l i ty that improvements in
knee funct ional capaci ty may have plateaued at th is t ime.
Further research is required to test the relat ionship between
EMG median frequency and knee funct ional capaci ty at d i f ferent
phases of the post-operat ive rehabi l i ta t ion program.
Al though the subjects di f fered in age, th is did not appear to
inf luence the knee funct ional abi l i ty as the corre lat ion between
the knee funct ion rat ings and the age of the subjects was not
s igni f icant . I t is shown that maximal muscle torque and
myokinase act iv i ty seems to change according to age such that
the decl ine of myokinase act iv i ty can account for the factors
which inf luence the decl ine in muscle torque with age (Borges
and Essen-Gustavsson, 1989). The sensi t iv i ty of the Cinc innat i
rat ing scale in evaluat ing knee funct ion has also been
quest ioned and may have been a source of var iabi l i ty and error
in th is analysis. This l imi ted sensi t iv i ty may be part icular ly
s igni f icant dur ing the later s tages of the rehabi l i tat ion process
when subjects are approaching normal levels.
Comparison of the Cincinnat i rat ing scale wi th another system
der ived by Lysholm and Gi l lquist (1982) ident i f ied the need for
more accurate instruments in the evaluat ion of the knee
surgical outcomes (Demirdj ian et a l . , 1998). In response to th is
chal lenge, Barber-West in et a l . , (1999) conducted a r igorous
159
analysis of the sensi t iv i ty of the Cincinnat i Knee Rat ing System
in 350 subjects. Of these subjects, 250 had ACL reconstruct ion
s
s
d
w
v
2
o s used to assess the val id i ty and
sensi t iv i ty were the Musculoskeleta l Funct ion Assessment
Quest ionnaire (Engelberg et a l . , 1996) and Short Form-36
(Ware and Shelbourne. , 1992, McHorney et a l . , 1993), isometr ic
strength, A-P laxi ty and cl in ical examinat ions of the knees that
produced good resul ts wi th over 90% showing low “ f loor” and
“cei l ing” ef fects and over 85% of the i tems showing large
ef fects (>0.80) ranging f rom 1.07 to 2.48 (Barber-West in et a l . ,
1999). According to Stucki et a l . , (1995) good val id i ty is
presented when few f loor or cei l ing ef fects are found. This
indicated that the Cincinnat i Knee Rat ing System demonstrated
r
using the bone pate l lar- tendon bone graf t . The rel iabi l i ty of the
ystem was determined from 100 non-ACL reconstructed
ubjects who completed the quest ionnaire twice, a mean of 7
ays apart . Resul ts showed a high test and re-test re l iabi l i ty
i th inter-c lass correlat ion coeff ic ient greater than 0.70. The
al id i ty and sensi t iv i ty of the system were examined from the
50 ACL reconstructed pat ients for a minimum of 2 years post-
perat ive observat ion. I tem
acceptable rel iabi l i ty , va l id i ty and sensi t iv i ty for the use in ACL
econstruct ion.
160
In sum
w that, in ACL reconstructed
subjects, there were no signi f icant bi la teral d i f ferences in the
EMG median f requency in selected extensor and f lexor
muscles of the knee of the in jured l imb. The f inding of a
di f ference in EMG median f requency of muscles of the non-
injured knee and the age matched normal subjects suggests
that use of the contralateral l imb for comparat ive purposes
may be inappropr iate.
In addi t ion, resul ts in th is study a lso show that the EMG
median f requency shi f t of the VL, MH and VM in the ACL
reconstructed knee is inconsistent among subjects.
Consequent ly, us ing EMG median frequency as an indirect
method to infer the type of muscle f ibres which atrophies
subsequent to ACL reconstruct ion is inconclusive at th is s tage.
Further research with larger sample s ize is required to
substant iate a common EMG median frequency shi f t in the
muscles.
Restorat ion of knee funct ion 6 months post-operat ively
approached normal level and there was no relat ionship
between funct ional abi l i ty and the discrepancy in EMG median
frequency between the reconstructed and contralateral l imbs.
The resul ts were inconclusive wi th respect to the use of EMG
median frequency as an indirect predictor of changes in
muscle f ibre composi t ion fo l lowing ACL reconstruct ion.
Further research is needed wi th a larger group of subjects and
mary
The resul ts of th is study sho
161
incorporat ing long esigned to invest igate
changes in EMG median frequency across the ear ly stages of
i tudinal analysis d
the rehabi l i tat ion cont inuum.
162
Chapter Six
General discussion, summary and conclusions
6.1 General discussion
Ident i f icat ion of muscle f ibre type is most direct ly and accurately
determined by biopsy technique, but the invasive nature of th is
procedure makes i ts appl icat ion inappropr iate as a rout ine
measurement tool . EMG median f requency has been previously used
to predict muscle f ibre composi t ion in a group of ACL def ic ient
subjects (McNair and Wood, 1993). However, the rel iabi l i ty and
l id i ty of th is technique was quest ioned (Kupa et al . , 1995, McHugh
1990 and Devi ta et .a l . , 1997).
h is adaptat ion leads to atrophy of the knee extensor musculature
is unclear due to the lack of
va
et al . , 2002a) and some revis ion and improvement was considered
necessary to fur ther val idate the procedure. Ref inement of th is
technique and val idat ion as a predictor of muscle f ibre composi t ion
would be valuable in any rehabi l i ta t ion process fol lowing an in jury in
which muscle atrophy occurs. For example, ACL in jur ies are
associated with anter ior instabi l i ty of the knee (Good et .a l . 1984 and
Wexlet et .e l . , 1998), resul t ing in the “quadr iceps avoidance” gai t as
a funct ional adaptat ion (Noyes, et . Al ,
T
and select ive atrophy of associated muscle f ibres and funct ional
def ic i t (Edstrom, 1970, Nakamura et a l . , 1986, Gerber et a l . , 1985,
McNair and Wood, 1993). However, evidence with respect to the
speci f ic f ibre type involvement in ACL related atrophy is
inconclusive. In addi t ion, def in i t ion of the most ef fect ive
rehabi l i tat ion to restore normal funct ion
163
informat ion on the speci f ic t iming of commencement and the design
of the rehabi l i tat ion program, wi th respect to a part icular muscle
bre type, in response to di f ferent speeds of t ra in ing exercises.
edian f requency changes fol lowing ACL in jury
or rec nstruct ion and a better understanding of the muscular
nd the least bi lateral d iscrepancy in
determining EMG median frequency of a muscle? and 2. What is the
ty of the determinat ion of EMG median frequency to
enhance i ts use as a predictor of muscle f ibre composi t ion. This may
f i
The present research was designed to provide a more accurate and
rel iable protocol in the determinat ion of EMG median frequency
which can be used to improve i ts use as a rout ine non- invasive
method to infer muscle f ibre composi t ion. Evaluat ion of the stabi l i ty
of th is measure over a var iety of condi t ions provides a c learer
picture of the EMG m
o
response under varying muscle contract ion condi t ions.
Accordingly, the purpose of th is invest igat ion, as a f i rst stage of the
val idat ion process, was designed to address the fol lowing quest ions:
1. What is the most stable mode of muscle contract ion in terms of
the lowest var iabi l i ty a
muscular response as measured by EMG median frequency to
varying speeds of muscle contract ion, fat iguing exercise and atrophy
fol lowing ACL reconstruct ion.
The ul t imate goal of the present research program was to improve
the rel iabi l i
inform the implementat ion of improved ACL rehabi l i tat ion programs
designed to restore and prevent loss of speci f ic muscle f ibre types
inferred by the EMG median frequency.
164
The in i t ia l invest igat ion reported in Chapter Three was designed to
establ ish the rel iabi l i ty of EMG median f requency under a range of
condi t ions which included the speed and the mode of musc
Study One
le
contract ion. The resul ts showed that isometr ic contract ion was the
le mode of muscle contract ion in determining EMG
median frequency when compared with other speeds of dynamic
The EMG median f requency di f fered between indiv idual knee f lexor
most rel iab
muscle contract ion.
No signi f icant di f ferences in EMG median frequency were found
between the muscle of the dominant and non-dominant l imbs, which
indicated that in normal s i tuat ions, muscles of the contra- lateral
knee can act as a control . This f inding agrees with previous studies
of normal subjects (DeLuca et a l . , 1986, El fv ing et a l . , 2000,
Lindstrom et al . , 1995).
and knee extensor muscles suggest ing that when using this
measure, each muscle should be considered separately. No
signi f icant gender di f ferences were found in th is measure suggest ing
that male and female subjects may be combined when using this
measure.
By comparison, decreased rel iabi l i ty ( including the bi latera l
asymmetry and between t r ia l standard deviat ion) was associated
with higher speeds of isokinet ic contract ion up to 240° per second.
165
This was consistent wi th previous studies (McHugh et al . , 2002b,
Potvin, 1997). However, whether or not th is phenomenon is solely
an outcome of the exper imental l imi tat ions as descr ibed by Kupa and
col leagues (1995), is unknown. Al though the resul ts showed a t rend
towards bi lateral asymmetry in EMG median frequency, th is
S
of the vastus
r ther
indica that s low twi tch f ibres ( type I ) were more act ivated than the
st twi tch ( type I I ) muscle f ibres (Warren et a l . , 2000). A
elat ionship between the changes in EMG median frequency and the
uscle f ibre type composi t ion which was establ ished f rom ear l ier
d i f ference was not s igni f icant wi th increased speed of contract ion.
tudy Two
The second study invest igated the changes in EMG median
frequency fol lowing fat iguing exercise performed at di f ferent speeds.
Subjects comprised of 34 normal adul ts and the EMG analyses and
procedures for the determinat ion of EMG median frequency were
consistent wi th those determined in Chapter Three. A s igni f icant
decrease was found in the EMG median frequency
lateral is af ter fat iguing exercise which was consistent wi th ear l ier
research (Sadoyama et al . , 1983, McHugh et al . , 2001, Masuda et
al . , 1999, Stulen and De Luca, 1981, Broman et a l . , 1985).
Resul ts also showed that the percentage of decrease in EMG median
frequency of vastus lateral is was signi f icant ly higher wi th s low speed
exercise than fast speed exercise. By reference to ear l ier research
(McNair and Wood, 1993), th is may ref lect a corresponding decrease
in the conduct ion veloci ty of the muscle f ibres. I t may fu
te
fa
r
m
166
research (McNair and Wood, 1993, Kupa et al . , 1995), suggests that
in the resul ts of Study Two, s low twi tch f ibres ( type I) are act ivated
ate intensi ty are required. Previous
knowl dge concerning speci f ic muscle f ibre type changes in
af ter s low speed exercise and fast twi tch f ibres ( type I I ) were
act ivated af ter fast speed exercise.
No signi f icant di f ferences were found in the recovery of EMG median
frequency measures of the vastus lateral is af ter s low or fast speed
fat iguing exercises. EMG median frequency returned to the pre-
exercise level af ter the recovery per iod of 7 minutes. This agrees
with a previous study which indicated that EMG median frequency
returned to normal levels wi thin 10 minutes af ter a protocol of
isometr ic exercise which was cont inued unt i l subjects could not
achieve or maintain the desired tension level (Cornwal l et a l . , 1994).
There is a possibi l i ty that some subjects in the present study may
have returned to the normal level before 7 minutes.
I t is suggested from previous research (Kannus, 1994) that in order
to produce a longer term adaptat ion of speci f ic muscle f ibre types,
such as an increase in s ize or s trength, repeated sessions of
exercise with the appropr i
e
response to a speci f ic speed of t ra ining is l imi ted. The resul ts of
th is invest igat ion provide some prel iminary guidel ines towards a
more targeted approach to the rehabi l i tat ion program for the ACL
reconstructed subjects by speci fy ing the speed of exerc ise.
167
Study Three
The third study invest igated the changes in EMG median frequency
of the knee muscles of a group of ACL reconstructed subjects 6 to
12 months post surgery. The EMG median frequency of selected
muscles of the uninvolved l imb of an ACL reconstruct ion group was
signi f icant ly di f ferent to that of the corresponding muscles of normal
subjects of comparable age reported in Study One. Simi lar
di f ferences were found in the mean EMG median frequency between
the vastus latera l is and vastus medial is of the uninjured l imbs of the
ACL def ic ient group and the r ight legs of the control group (van Lent
predict the
type of muscle atrophy is inappropr iate. However c l in ical ly, the
1986), 6 weeks to 10
et a l . , 1994). These f indings suggested that muscular adaptat ion in
response to ACL def ic iency may have occurred in both l imbs (Devi ta
et a l . , 1997). Consequent ly, using the contra- lateral l imb as a
control to determine the EMG median frequency shi f t to
bi lateral asymmetry in the EMG median frequency of a muscle f ibre
may also serve as an indicator of funct ional def ic iency and inform
the rehabi l i tat ion process.
Study Three also showed that there were no signi f icant bi latera l
d i f ferences in the shi f ts of the EMG median frequency of the muscles
found in the ACL reconstructed subjects 6 to 12 months post-
operat ively. This resul t indicates that there was no common
consensus with respect to the part icular type of muscle f ibre that
atrophies subsequent to ACL reconstruct ion. Di f fer ing from previous
studies which examined subjects wi th ACL in jury or reconstruct ion
ranging from 3 to 50 months (Nakamura et a l . ,
168
years (Gerber et a l . , 1985) and 4 days to over one year (Baugher et
a l . , 1984), the present invest igat ion focused only on ACL
econstructed subjects wi thin a per iod of 6 months. The resul t of
ACL def ic ient subjects (van Lent et a l . , 1994).
r
th is study di f fers f rom that of ear l ier studies which found type I
muscle f ibre atrophy (Nakamura et a l ,1986 and Edstrom 1970); and
type I I muscle f ibre atrophy (Baugher et a l . (1984) and McNair and
Wood, 1993) fo l lowing ACL injury. However, resul ts of the present
study are simi lar to those of Gerber et a l . (1985), who found that
speci f ic muscle f ibre type atrophic changes were not consistent
among subjects.
For the above reasons, i t is suggested that i f future studies val idate
EMG median frequency, a shi f t in th is measure may be used as part
of the rehabi l i tat ion protocol , to detect the bi lateral asymmetry pr ior
to the muscular t ra in ing at any stage of rehabi l i tat ion.
The knee funct ional scores obtained using the Cincinnat i Rat ing
System of the ACL reconstructed subjects were not corre lated with
age, the post-operat ive t ime between 6 and 12 months, or the
bi lateral EMG median f requency discrepancy of the selected
muscles. This resul t is s imi lar to that obtained from a comparat ive
study of the post-operat ive muscle funct ion fol lowing ei ther a s ingle
or two- incis ion technique used in ACL reconstruct ion. The resul ts
indicated that the funct ional score did not correlate wi th the
isokinet ic evaluat ion (Hess et a l . , 2002). In contrast , s igni f icant
correlat ions were found between the Lysholm score and EMG
parameters of the vastus lateral is and vastus medial is in a group of
169
6.2 Summary, Clinical Implications, Conclusions and
Recommendations
Consi erat ion of the f indings from the three studies suggests that in
to val idate EMG median frequency
as a predictor of muscle f ibre composi t ion. I f conf i rmed knowledge
d
determinat ion of the EMG median f requency of the quadriceps and
hamstr ings muscles, the isometr ic mode of contract ion performed for
a per iod of 8 seconds is the most rel iable and is recommended as a
sui table procedure for determining the EMG median frequency. The
EMG median frequency of the vastus lateral is decreases more af ter
s low speed fat iguing exercise than af ter fast speed exerc ise. Also,
there is inconsistency in the bi latera l EMG median frequency shi f t
among ACL reconstructed subjects. Wi th reference to previous
research (McNair and Wood, 1993; Kupa et al . , 1995), EMG median
frequency of a muscle may be used to infer muscle f ibre composi t ion
of the muscle. However further research is required to conf i rm the
relat ionship between EMG median frequency and muscle f ibre
composi t ion der ived from a muscle biopsy before this technique
could be rel iably appl ied. The resul ts of th is study wi l l serve to
improve the rel iabi l i ty of procedures used to determine EMG median
frequency under a range of d i f ferent contract i le condi t ions. This in
turn wi l l enhance the opportuni ty
of EMG median frequency may be of value in areas of rehabi l i tat ion
where muscle atrophy is a known outcome, such as in condi t ions of
ACL def ic iency or fo l lowing reconstruct ion of th is l igament.
Measurement of EMG median frequency using the recommended
mode of muscle contract ion as ear ly as possible in the rehabi l i tat ion
170
process could be used to help determine the speci f ic type of
isokinet ic rehabi l i tat ion program needed to target speci f ic muscle
f ibres, part icular ly wi th respect to speed of contract ion.
The speed of isokinet ic exercises to be adopted in an ACL
rehabi l i ta t ion program would depend on the type of muscular def ic i t
inferred by the EMG median frequency evaluat ion. For a type I
muscle f ibre def ic i t , an exercise program wi th a s low speed of 30°
per second would be recommended. On the other hand, a fast speed
exercise program is recommended for type I I f ibre def ic i t (F igure
6.1). Important ly, the use of EMG median frequency would
compl iment the exist ing pr inciples of ACL rehabi l i tat ion programs
and may improve outcomes. These pr inciples include: a delay of
reconstruct ion unt i l at least 3 weeks post ACL in jury (Shelbourne et
a l . , 1995); The use of cont inuous passive movement of the knee
dur ing the ear ly pos-operat ive stage (Noyes et a l . , 1987) the
appl icat ion of isokinet ic technology (Kannus 1994, Chan et al 1996);
the use of c losed kinet ic chain exercise (Palmit ier et a l . , 1991, Yack
et a l . , 1993); and the importance of achieving a hamstr ing to
quadr iceps strength rat io approaching one (Giove et a l . , 1983, Li et
a l . , 1996, Aagaard et al . , 1998).
A considerable number of ACL rehabi l i tat ion programs have been
implemented and previously reported (Shelbourne and Nitz, 1990,
Shelbourne et al . , 1992, Wi lk et a l . , 1992, Mangine and Noyes, 1992,
Malone and Garret t , 1992, De Carlo et a l . , 1992, De Carlo et a l . ,
1999, Case et a l . , 1991, Blair and Wil ls , 1991, Fu et a l . , 1992,
Stanish and Lai , 1993, Shelbourne and Rask, 1995). These programs
171
range from an accelerated program which prescr ibes the use of ear ly
knee hyperextension, ear ly post-operat ive weight bear ing; and ear ly
return to pre-ACL injury levels in sport ing act iv i t ies (Shelbourne and
Nitz, 990), to a more conservat ive approach which does not
encou ge ful l sport ing act iv i t ies wi thin 12 months af ter the
operat ion (Malone and Garret t , 1992). The rat ionale for each of
these approaches is considered sound by the medical pract i t ioners
involv d but more informat ion is required to determined the opt imal
implementat ion procedures and their ef f icacy. Fol lowing appropr iate
val idat ion of EMG median f requency with direct biopsy techniques, i t
may be included in these programs as a predictor of changes in
muscle f ibre composi t ion, as indicated in previous research (Kupa et
al . , 1995). Inclusion of EMG median frequency may provide a
reater degree of speci f ic i ty in the training of speci f ic muscle f ibre
pes fol lowing post in jury atrophy. A hypothet ical model for the
tegrat ion of EMG median f requency into exis t ing models of ACL
ehabi l i tat ion is shown in Figure 6.1. Reference is made to new
format ion der ived from this invest igat ion.
1
ra
e
g
ty
in
r
in
172
Recovery Stages Treatment Protocol
Fig on pro int and hiCPcha in . IE=Isok ine t ic exerc ise , R igh t sh i f t= inc rease in EMG median f requency. Le f n f requency .
6.1 A schematic presentat ion of a suggested ACL rehabi l i tat itocol integrat ing f indings ar is ing out of th is research ( in bold pr
ghl ighted boxes) in to the exist ing protocol ( in i ta l ics) M = con t inuous pass ive movement , CKC and OKC=open and c losed k ine t ic
t sh i f t=decrease in EMG med ia
CPM Start stat ic exercise
Determine EMG MF using the 8-s 0°/s to identify
bilateral asymmetry
Right shift = type I deficit Slow speed IE
30-60°/s CKC exercise
Left shift =
180-240°/s
type I I deficit
Fast speed IE
CKC exercise
Determine EMG MF using the 8-s 0°/s to identify bilateral asymmetry
Right shift=
30-60°/s
H:Q=1(Li et al., 96)
type I deficit
Slow speed IE
OKC exercise
Left shift =
180-240°/s
H:Q=1(Li et al.,96)
type I I deficit
Fast speed IE
OKC exercise
When return to pre-in jury level o f spor t is
a l lowed
When l ight sport is
allowed
Determine EMG MF using the 8-s 0°/s to
If occurs, continue IE identify bilateral asymmetry
When walk ing independent ly
In i t ia l phase post -operat ive ly
Commence act ive exercise
When isok inet ic exerc ise is a l lowed
Duration orecovery stage varies accordingpreference of individual surgeon a
f each
to the
nd therapist
173
6.3 Conclusions
On
con
VL, HM and VM were examined
together, there was no bi lateral EMG discrepancy in median
ral l imb can act as controls.
eeds up to 240° per second. However, these trends did
ot reach signi f icance.
the basis of the resul ts of th is invest igat ion, the fol lowing
clusions can be made:
Study One
The most rel iable mode and speed of muscle contract ion for
determining EMG median frequency in terms of the least bi lateral
d iscrepancy and lowest var iabi l i ty was 0° per second across a
range of test ing speeds up to 240° per second. Isometr ic
contract ion is the recommended mode for determining EMG
median f requency of a muscle. In the present study, an 8-second
durat ion was adopted.
When both male and female subjects were combined and al l the
three selected muscles of
f requency at any of the test ing speeds. As such in the
determinat ion of EMG median frequency, corresponding muscles
of the contralate
There was a t rend towards an increase in the percentage bi lateral
d iscrepancy of EMG median frequency wi th increased test ing
speeds across 0° to 240° per second. Simi lar ly, there was also a
t rend towards increasing inter- t r ia l var iabi l i ty wi th increased
test ing sp
n
174
When the three selected muscles were examined indiv idual ly, the
observat ion towards increasing percentage bi lateral d iscrepancy
with increased
speed was st i l l apparent, but again not s igni f icant.
uency
of vastus medial is was apparent in both genders. The EMG
equency of each muscle should therefore be determined
nd interpreted indiv idual ly. This appl ies to muscles even within
There were no gender di f ferences in the EMG median f requency
percentage bi lateral EMG median frequency
discrepancy found in any of the three muscles and at any of the 5
gether, there was no signi f icant in ter- t r ia l var iabi l i ty
found at any of the 5 test ing speeds across 0° to 240° per
A s igni f icant elevat ion of the EMG median frequency was found in
the vastus medial is as compared to that of the vastus lateral is
and medial hamstr ings. When male and female subjects were
studied indiv idual ly, the elevat ion of the EMG median f req
median fr
a
the same group, for example, the vastus medial is and vastus
lateral is or the biceps femoris and semitendinosus.
across al l muscle groups.
There was no
test ing speeds.
When both male and female subjects were combined and al l the
three selected muscles of the lef t and the r ight l imbs were
examined to
second.
175
ia l is as compared to that of vastus lateral is and media l
h mstr ings.
There was a s igni f icant decrease in the EMG median f requency of
he percentage drop in EMG median frequency of the vastus
t and slow speed
exercise.
vastus lateral is 7 minutes af ter s low or fast speed fat iguing
When the three selected muscles were examined indiv idual ly,
there was a s igni f icant increase in the inter- t r ia l var iabi l i ty in
vastus med
a
When the EMG median frequency of the three muscles of the
dominant and non-dominant l imbs and also the male and female
subjects were studied separately, a s igni f icant increase in the
inter- t r ia l var iabi l i ty in vastus medial is was st i l l apparent.
Study Two
Resul ts showed there were no gender or bi la teral d i f ferences in
the EMG median frequency of the vastus lateral is of a group of
heal thy subjects. This conf i rms the resul ts of Study One.
the vastus lateral is in response to fat iguing exercise at fast and
slow speeds.
T
lateral is was signi f icant ly higher af ter s low speed exercise than
fast speed exercise. No di f ference was found in the percentage
of the extension torque drop between fas
No di f ferences were found in the in EMG median frequency of the
176
exercises. This indicated that the EMG median frequency had
returned to the pre-exercise level af ter the recovery per iod of 7
minutes.
d) exercise, and fast twi tch f ibres ( type
I I ) were act ivated with fast speed (300° per second) exercise.
Stu
as s igni f icant ly higher than that of the
corresponding muscles of normal male subjects in Study One.
ACL reconstruct ion group and the normal group.
The percentage bi la teral EMG median f requency discrepancy for
al l the three selected muscles of the ACL reconstruct ion subjects
On the informat ion presented in previous research, resul ts of the
present study suggested that s low twi tch f ibres ( type I) in the
vastus lateral is of 34 heal thy subjects were more act ivated with
s low speed (30° per secon
dy Three
The mean EMG median f requency of the vastus lateral is and
medial hamstr ings of the uninvolved l imbs of the ACL
reconstruct ion subjects w
No signi f icant di f ferences were found in the mean EMG median
frequency of the vastus medial is of the uninvolved l imb of the
There were no di f ferences in the mean bi lateral EMG median
frequency between the ACL reconstructed l imbs and the
uninvolved l imbs among the VL, MH and VM.
177
was signi f icant ly higher than the corresponding muscles of the
normal male subjects in Study One.
The mean EMG median frequency of the media l hamstr ings and
The absolute EMG median f requency shi f ts of VL, MH and VM of
the ACL reconstructed l imbs in relat ion to the uninvolved l imbs
were inconsistent among the group of subjects 6 to 12 months
fo l lowing semitendinosus and grac i l is graf t ACL reconstruct ion.
There was no general ized b i lateral EMG median f requency shi f t
found in these subjects.
The mean isometr ic f lexor st rength of the uninvolved l imb was
higher than that of the ACL reconstructed l imbs. No di f ferences
were shown in the mean extensor st rength between the two l imbs.
When compared to normal age matched values, the mean relat ive
hamstr ings and quadr iceps strength (H:Q rat io) was considered
high, by reference to normal values, both in the ACL
reconstructed l imbs (74.39%) and in the uninvolved l imbs
(77.92%).
vastus medial is of the ACL reconstructed l imbs was higher than
that of the corresponding muscles of the uninvolved l imbs.
However, th is measure was lower in the vastus lateral is of the
ACL reconstructed l imbs.
178
There was no correlat ion be he H:Q rat io of the ACL
uency shi f t of any of
correlated with
the percentage bi lateral d iscrepancy of the EMG median
tween t
reconstructed l imbs and the EMG median freq
the three selected muscles.
The Cincinnat i knee funct ional scores were not
f requency, age and the post-operat ive t ime of the ACL
reconstruct ion subjects.
179
6.4 Recommendation for es
f ts such as the bone pate l lar- tendon bone and the quadr iceps
further studi
A longitudinal investigation of the changes in EMG median
frequency in relation to the nature, frequency and duration of
exercise should be emphasized in future research.
Val idat ion of EMG median frequency against muscle biopsy
techniques using the procedures establ ished in th is invest igat ion
to enhance the rel iabi l i ty of EMG median frequency.
Evaluat ion of the ef f icacy of the hypothet ical model of integrat ing
the f indings of the present research into exis t ing models of ACL
rehabi l i tat ion shown in Figure 6.1 us ing a large populat ion of
homogenous ACL reconstructed subjects.
Comparison of the di f ferences in the EMG median frequency
shi f ts between subjects receiv ing di f ferent ACL reconstruct ion
gra
graf ts.
180
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n
.
202
Appendices
203
A. Raw data for individual s and addit ional graphical
representat ion of group data for Study One
B. Ethical Approvals
C. Subjects recruitment information materials for Studies One
and Three
D. Subject information package and Consent forms for
Studies One, Two and T approved by the UHREC,
QUT
E. The Cincinnati Rati g sheet (Modif ied)
F. Other forms and information
• O the Holy Tr
• Resul ts of the Window pi lot study
G. Publicat ions and presented papers
ubjects
hree
ng System Scorin
• The PAR-Q form ut l ine of ACL rehabi l i tat ions program used by in i ty Hospi ta l
204
Ap di
pen x A
Raw data for individual subjects add al ic
pres ion ou a e
atistic infor tion tu e
and ition graph al
re entat of gr p dat and th
st al ma for S dy On
205
Musc les L VL R VL L VL R VL L VL R VL I Sp d 0 0 6 s 6 s 12 /s 12 /s d . ee ° /s ° /s 0° / 0° / 0° 0°
M1 M 53.75 55.1 56.37 57.4 54.56 57.6 M2 M 47.6 56.6 52 61.4 81 60.8 M3 M 56 55 59 53.6 56.8 57.8 M4 M 54.2 52.25 67.6 71.2 67 74.2 M5 M 56.83 63 64 .1 64 .8 67 .2 72 .2 M6 M 61.5 55.75 60.34 69.55 60.58 66.88 M7 M 50.63 54 62.31 66.42 48.81 50.24 M8 M 61.2 56.4 54.96 52.31 49.72 51.87 M9 M 59.4 56.25 59.03 70.09 54.54 63.77
M10 M 73.75 73.5 8 8 .61 76.09 74.93 69.51 M11 M 46 49.63 62.86 62 52.96 59.82 M12 M 67.75 63.17 75.27 66.14 65.26 54.57 M13 M 85.5 8 5 0 .2 94.44 95.2 91.07 76.8 M14 M 62.4 56.2 54.81 5 2 9 .2 55.5 61 .73 M15 M 61.75 61.75 59.64 62.62 49.07 53.94 M16 M 52 51.5 56.16 53.7 60.39 61.24 M17 M 65.2 62.75 52.79 65.2 50.14 72.6 M18 M 62.75 64 55.29 52.12 58.11 56.75 M19 M 62.75 59 66.27 63.6 65.09 61.2 M20 M 58 55.5 55.74 60.3 53.61 55.38 M21 M 59.68 60.82 60.41 6 7 .97 62.19 66.77 M22 M 74.75 75.75 74.43 78.74 84.88 76.58 M23 M 59 66 7 8 .05 83.99 73.51 76.55 M24 M 60 62 31.65 48.05 43.69 46.9 M25 M 55 62 59.72 56.81 44.82 44.91 M26 M 68.2 67 61.75 57.09 51.68 58.45 M27 M 73.64 71.5 77.89 80.45 6 6 .61 70.75 M28 M 58.65 51.75 73.82 63 .39 53 .5 54 .09 M29 M 55.75 51.5 6 2 .58 65.92 44.32 55.16 M30 M 60.9 62 68.3 68.32 64.66 61.83 M31 M 59.25 61.5 64.35 68.5 61.09 55.13 M32 M 49.75 50.75 69.1 56.24 59.34 56.22 M33 M 57.5 59.75 54.92 6 5 .94 50.37 61.54
Tab le 3A.1
E ian ncy in nd i a l t s S e
MG medtudy On
f reque resu l ts Hz fo r i v idua l m e sub jec of
L=Lef t R=Right VL = Vas tus la tera l i s
MH=Media l hamst r ings VM=Vastus med ia l i s
206
L VL R VL L VL R VL L MH R MH L MH R MH
180°/s 180°/s 240°/s 240°/s 0°/s 0°/s 60°/s 60°/s
82.22 60 51.92 63.4 74 73 71.6 71.8 58.2 59 54.2 60.06 82.8 80.6 64.8 62.6 57.6 77.4 60.6 80.4 77.6 58.25 62.5 74 48.6 69.8 54.8 73.2 65.4 56.75 57.75 70 70.6 70.2 71.8 53.2 65.5 63.56 55.2 64.3
59.87 68.55 50.87 63.96 53.75 51.17 56.52 5 8.3651.83 70.5 55.87 56.94 53.4 54.75 58.05 63.39 51.73 50.94 52.41 51.48 63.6 65.4 45.16 55.83 54.84 63 60.65 63.56 65.25 64.25 63.98 66.79 74.74 55.23 72.88 66.94 68 65.32 78.89 76.25 43.28 66.73 45.54 55.73 57.23 54.44 6 7.65 62.24 65.89 60.6 62.55 64.84 44.5 44.25 74.46 71.07 90.68 72.4 93.72 52 45.5 52.75 72.01 73.55 55.91 68.32 51.81 60.29 54.2 53 60.01 57.19 50.91 82.04 90.2 56.83 76.75 79.2 54.83 66.92 56.92 54.79 54.67 45.62 57.57 58.75 63.24 57.18 37.89 66 68.7 51.4 66.17 67.88 71.86 69.48 62.21 57.39 59.82 76.5 49.17 49 52.27 52.26 58.08 60.4 57.78 62.8 49.17 49 56.51 58.4 60.99 55.46 56.73 53.65 60.75 62 75.25 70.89 58.81 63.28 60.89 69.39 48.25 51.5 60.24 64.42 85.11 55.23 59.88 73.87 58 55.25 60.33 65.66 65.52 74.89 83.63 58.84 72.6 75.8 63.09 56.21 55.34 33.05 55.81 28.57 75.5 77 22.82 21.43 54.85 49.2 57.43 33.33 62.6 63.2 62 60.55 77.16 51.05 61.06 40.27 64.8 63.11 50.49 56.63 51.52 71.84 68.81 52.62 67 67.75 58.94 60.38 47.57 67.45 57.12 55.3 71.75 73.15 87.09 87.94 52.84 60.38 54.82 38.09 46.25 49.6 82.4 81.54 62.87 67.19 70.54 63.57 73.75 71 64.27 66.29 67.09 57.48 48.12 75.6 64.25 62 6 7.14 63.45 68.46 43.63 63.65 65.73 58.25 55.75 58.95 6 3.5650.47 65.91 55.66 61.99 66.75 68.25 82.34 80.31
L=Lef t R t VL Vastus
a l
s
T EMG median frequency resul ts in Hz for ind iv idua l male subjects of Study One
=Righ =
la tera l is MH=Medihamstr ings VM=Vastumedia l is
ab le 3A.1
207
L MH R MH L MH R MH L MH R MH L MV R MV
120°/s 120°/s 180°/s 180°/s 240°/s 240°/s 0°/s 0°/s
72.99 59.8 62.24 6 1.8 57.32 80.4 94.5 91.75 68.4 55.9 75.4 56.4 68.4 83.4 70.6 73.2 69.8 65 52.8 49.5 74.4 54.2 4 4.75 46 69 72 85.4 65.2 57.6 64.6 73 75 56 64.6 5 4.4 64.32 55.5 69.4 66.25 65.75
41.87 53.38 39.04 52.4 36.59 57.51 74.75 78 52.97 67.49 57.89 69.89 88.3 56.82 70.75 72.81 45.59 49.06 54.31 46.36 56.1 67.02 60.4 61.2 76.66 78.39 78.46 71.83 52.67 72.24 73.63 74.93 63.54 64.44 82.54 67.46 92.3 74.59 75.5 77.25 35.56 51.34 66.8 53.19 71.99 50.59 60 56.79 67.7 56.12 80.54 63.68 82.28 60.47 85.25 79.17
56.56 65.53 56.91 55.07 60.2 4 3.86 78.75 79.5 57.56 60.47 60.42 50.92 72.84 58.95 58.8 64.8 55.12 50.68 63.18 51.36 66.63 52.35 92.75 92 48.41 58.36 50.13 66.43 56.7 68.77 55.75 50.5 50.29 27.49 58.4 27.04 59.23 35.62 78.25 73.5 50.02 52.88 44.01 54.48 45.57 54.82 87.89 85.67 51.02 53.8 48.5 5 4.6 50.78 55.8 87.89 85.67 72.51 60.22 68.74 65.55 80.95 63.38 85.5 82.75 48.89 70.65 51.74 63.3 48.18 63.78 68.38 69.75 48.18 59.19 55.49 56.66 54.39 61.64 74.75 70.75 58.53 51.63 59.56 69.48 65.07 61.4 73.25 74 49.55 54.44 46.86 53.16 26.32 52.19 59.59 63.8
64 61.35 46.71 66.77 87.24 68.48 73.8 72.2 49.68 48.24 51.21 55.03 46.61 56.18 60.4 63.91 59.23 59.23 50.09 58.76 43.63 53.08 67.06 64.92 60.97 67.27 65.95 68.64 55.69 67.39 97.4 98.94 68.41 58.62 71.74 60.26 86.31 45.82 77.75 75.25 58.83 63.31 57.36 62.38 45.2 58.15 76 76.5 53.11 56.68 59.41 49.91 58.71 30.68 75 74.73 51.95 50.4 55.89 47.64 56.77 54.44 68.5 72 69.37 72.01 81.76 76.48 83.55 69.72 69.5 72.25 Table 3A.1
EMG median f requency resul ts in Hz for ind iv idua l male subjects of Study One
L=Lef t
R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
208
L MV L R L R LR MV MV MV MV MV MV MV 60°/s 12 12 1 1 2 260°/s 0°/s 0°/s 80°/s 80°/s 40°/s 40°/s
85.67 88 85.38 98 67.28 100.4 87.95 46.8
71 75.2 63.8 79.2 61.8 70.6 90.4 71.6 62.6 65.8 63.4 64.2 67.8 63.3 56.3 83 74.8 68.38 79.8 87.1 66.2 81.6 62.2 88.4 61.4 70.4 566 67.6 66.6 66.8 68.9 9.8
68.07 77.01 75.98 60.34 6 59.37 67.81 70.6 3.4 77.48 72 67 8 6 47.24 .65 58.9 .74 1.25 57 7.04 68.99 68.31 51.9 44.4 69.02 48.79 65.96 59.98 75.01 75.07 71.37 68.27 52.25 74.85 63.99 77.84 86.77 93.52 90.79 70.56 69.14 70.47 84.66 71.41 77.91 74.07 56.31 59.08 72.04 55.33 46.76 59.13 90.18 83.34 78.08 62.18 83.25 59.12 99.81 72.74 75.14 68.8 66.91 96 62.23 84 91.2 70.9 69.11 64.99 38.69 51.47 42.89 59.27 34.01 55.26 96.11 100.51 70.99 68.42 80.66 63.02 72.77 60.51 84.44 77.79 49.51 76.52 56.59 69.32 61.38 74.9 88.49 75.6 5 7 65.6 54 76.6 7.48 69.4 4.15 93.2 83.16 76.42 57.44 79.18 60.63 95.17 75.13
83.26 84.6 79 8 7 7.16 8 8.16 90.2 8.91 85.4 73.47 84.27 56.53 59.82 79.54 61.05 54.33 71.05 91.56 96.62 47.03 56.77 55.54 99.35 56.49 101.15 95.52 97.89 63.16 74.23 59.41 73.61 74.51 92.4 83.9 85.2 75.71 59.42 63.05 79.42 69.27 85.68
46.88 44.63 38.49 49.45 16.82 26.85 30.15 63.57 78.27 78.92 54.97 51.51 68.81 59.87 81.69 65.43 65.91 66.22 66.32 49.52 57.97 28.32 72.5 44.52 86.47 94.96 55.39 50.89 69.51 52.46 64.69 80.03 92.81 101.88 70.25 79.03 73.25 83.79 81.87 47.91 88.65 81.54 50.51 58.52 60.11 91.3 62.68 37.22 81.74 81.54 69.82 75.26 56.6 80.9 73.57 78.81
78 84.12 67. 66. 81. 67. 89. 70. 01 18 48 33 89 3383.45 79.05 73.61 84.72 61.47 81.39 63.38 89.43 71.97 67.59 54.05 79.33 62.82 89.71 66.62 86.57 Table 3A.1
EMG median f requency resul ts in Hz for ind iv idua l male subjects of Study One
L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
209
M uscles L VL R VL L VL R VL L VL R VL
Id. Speed 0°/s 0°/s 60°/s 60°/s 120°/s 120°/s
F1 F 57.5 57.5 70.86 74.6 70.2 58 F2 F 47.33 48.83 55 54.4 58 68.6 F3 F 51.25 52 60.8 58.6 66.4 53 F4 F 70.6 65 67.72 1 64.3 63.83 53.37 F5 F 56.25 59.75 6 69.84 60.1 63.77 65 F6 F 52.75 54.39 4 65.1 63.2 58.64 62.6 F7 F 45.75 52 68.69 61.92 56.53 55.28 F8 F 54.5 60.8 57.07 63.47 45.03 56.2 F9 F 65.5 63 62.58 64.62 65.74 39.44
F10 F 46 47.25 9 53.26 52.5 44.24 34.59 F11 F 47.5 47 54 59.59 51.29 63.46 F12 F 56.64 50 55.77 54.6 50.23 48.9 F13 F 64.75 63.14 4 75.61 81.6 63.5 75.6 F14 F 61.6 60.67 65.77 65.31 48.97 51.73 F15 F 62.67 58.33 62.58 65.92 44.32 55.16 F16 F 57.25 62.75 68.19 70.66 61.1 62.94 F17 F 44.75 49.75 66.62 55.38 56.13 43.6 F18 F 77.5 73.75 72.55 68.35 68.63 61.91 F19 F 64 65 68.43 74.34 57.76 64.34 F20 F 51.25 51.67 67.54 60.99 62.51 45.46 F21 F 65.4 66 87.49 76.85 65.23 64.33 F22 F 54.5 51.5 61.66 68.22 54.49 57.66
Table 3A.1
EMG median f requency resul ts in Hz for ind iv idua l female subjects of Study One
L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
210
L VL R VL L VL R VL L MH R MH L MH R MH
180°/s 180°/s 240°/s 240°/s 0°/s 0°/s 60°/s 60°/s
64.2 61.2 6 8.6 40.2 62.75 63.75 70.6 71.4 57.8 62.8 5 3.8 61.4 70.5 68 55.8 58.2 65.6 56.4 59.6 80.4 50.75 4 9.25 49.6 50.8
65.36 57.18 64.18 54.67 67.2 65 55.36 64.98 64.1 62.03 67.17 65.6 60.25 60 55.39 59.89
53.68 65.2 60.91 57.4 59 56.75 61.05 57.12 53.42 52.05 56.17 67.19 51.25 54.65 53.71 5 9.8151.44 56.4 49.61 79.9 69.5 68.75 52.17 52.75 57.54 23.99 32.03 62.33 61.25 64.5 47.43 44.96 43.64 26.39 21.2 57.4 47.4 48 49.85 44.56 53.62 74.47 53.59 56.27 51.5 56 45.66 50.79 52.64 72.71 56.39 50.44 84.21 82.43 6 9.07 74.31 52.66 71 71.67 54.4 61.17 63 75 70.1 55.92 77.5 81.5 53.47 56.99 41.32 57.17 68.92 42.84 60.38 54.82 58.09 63.5 61.25 82.4 7 1.5464.2 65.54 65.23 46.21 72.75 71.5 6 8.63 64.78
59.59 56.52 57.86 55.81 53.25 57.5 56.6 55.39 62.4 62.07 63.04 78.01 64.75 60.5 7 3.34 75.55
65.41 60.13 87.23 53 80 80.8 77.42 74.7 85.12 45.09 54.9 70.94 58.63 63.5 69.98 73.14 46.88 67.5 41.49 72.16 55.5 51.9 5 9.15 59.56 58.66 60.5 6 68.98 0.36 73.13 60.5 55.5 77.52 Table 3A.1
EMG median f requency resul ts in Hz for ind iv idua l female subjects of Study One
L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
211
L MH R MH L MH R MH L MH R MH L MV R MV
120°/s 120°/s 180°/s 180°/s 240°/s 240°/s 0°/s 0°/s
68.8 68.8 74 70.2 75.4 46.8 72.25 76.75 72.6 61.9 72 67.2 41.8 70.4 69.75 69.5 56.8 61.8 48.2 59.8 50.2 64 58.75 61.75
52.83 61.74 55.45 67.46 56.12 58.87 66.6 64.6 73.51 65.15 50.65 72.79 70.96 64.27 79.67 76.88 39.9 56.55 60.93 49.19 62.97 38.71 89.89 85.75
50.41 66.12 44.42 64.64 60.81 62.61 63.25 67 49.74 53.11 52.87 58.66 53.44 55.97 67.27 73.55 58.42 47.26 50.93 60.75 65.53 31.69 69.25 64.43 46.32 52.75 65.64 48.93 49.87 78.03 76.55 73.3 40.12 38.89 41.04 66.28 45.17 83.32 57 56.21 52.19 48.66 56.61 60.22 47.22 64.5 72 71.8 56.48 68.06 55.21 68.14 70.31 61.93 64 63.25 56.6 60.04 79.81 60.91 56 69.64 65.6 65.8
68.41 58.62 71.74 60.26 76.31 45.82 92.54 95 69.21 60.15 63.32 59.66 74.63 54.34 86 82.75 57.97 60.12 57.65 56.67 55.97 66.38 72.67 71 52.3 59.79 63.83 50.4 67 60.3 82 79.25
73.83 71.57 51.09 70.46 71.33 44.81 80.25 85.17 58.28 61.19 60.58 72.73 62.51 43.73 69.63 69.5 54.41 61.34 45.7 76.28 58.2 60.59 88 86.75 71.44 55.35 77 58.64 72.83 61.83 64.72 67 Table 3A.1
EMG median f requency resul ts in Hz for ind iv idua l female subjects of Study One
L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
212
L MV R MV L MV R MV L MV R MV L MV MV 60°/s 60°/s 120°/s 120°/s 180°/s 180°/s 240°/s 240°/s
84.2 83.4 79.6 87.32 77.6 85.5 75.8 87.6 74 75.2 74 64.2 71.12 65.5 41.85 77.2
62.2 58.4 68 55 63 56.6 84 49.4 80.01 72.41 44.54 57.1 68.03 57.56 55.45 69.25 99.63 115.75 58.02 83.19 68.35 79.6 68.15 98.74
110.99 99.2 75.35 88.4 73.11 90.04 86.58 76.8 67.67 66 72.32 61.47 72.75 67.27 67.22 81.89 74.08 83.07 55.89 47.73 76.03 55.63 85.13 55.01 64.75 66.99 60.67 37.37 73.27 41.51 71.42 27.6 64.53 72.86 82.77 87.95 39.85 99.47 41.56 75.48 62.66 58.76 46.07 51.72 50.4 42.28 77.39 47.52 77.38 67.1 51.99 50.9 60.72 54.54 62.25 54.85 80.49 80.8 51.75 76.6 54.63 68.4 82.07 65.46 80.39 82.7 44.22 52.29 52.5 60.75 67.38 58.66 88.65 81.54 50.51 58.52 60.11 91.3 62.68 37.22 87.67 93.27 67.85 75.34 64.63 69.6 57.26 79.84 80.27 79.18 60.78 56.63 67.9 60.4 71.3 63.76 84.01 74.43 51.87 47.99 72.31 64.93 88.18 62.8 86.51 93.41 37.55 46.39 36.2 66.22 25.34 57.18 79.1 72.6 36.7 43.66 56.49 44.07 86.79 58.85 89.6 91.42 70.4 75.54 73.95 84.21 52.29 88.05
79.18 79.66 40.78 37.06 81.84 51.18 73.12 53.07 Table 3A.1
EMG median f requency resul ts in Hz for ind iv idua l female subjects of Study One
L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
213
Muscles L VL R VL L VL R VL L VL R VL
Id. Speed 0°/s 0°/s 60°/s 60°/s 120°/s 120°/s
M1 M 11.4 6.2 4.32 8.78 4.98 6.38 M2 M 6.02 2.07 6 66.6 72.6 3.3 M3 M 7.05 2.71 4.17 5.59 5.54 8.49 M4 M 6.03 5.52 7.6 7.37 9.94 3.5 M5 M 5.54 5.71 7.39 8.39 10.68 4.51 M6 M 2.86 1.29 5.71 6.53 6.22 3.37 M7 M 7.49 7.21 3.39 5.86 5.59 6.8 M8 M 6.27 4.06 5.56 4.61 8.43 2.22 M9 M 5 6.38 8.84 2.18 8.58 4.64
M10 M 6.82 6.52 8.85 7.47 3.05 1.41 M11 M 9.57 4.02 6.67 1.84 8.93 1.34 M12 M 7.35 11.3 8.67 9.81 7.81 3.4 M13 M 7.89 7.35 9.82 5.81 9.56 6.57 M14 M 4.41 8.36 8.91 10.03 4.33 12.97 M15 M 2.28 3.72 4.97 6.36 9.64 2.52 M16 M 4.36 4.61 12.21 6.89 13.48 3.4 M17 M 2.91 4.34 4.38 4.65 4.46 9.42 M18 M 6.06 8.63 11.09 5.37 9.38 9.42 M19 M 6.25 5.07 4.11 4.6 8.35 5.32 M20 M 3.42 3.49 15.3 5.19 5.68 5.82 M21 M 4.85 8.49 6.66 7.19 11.27 5.11 M22 M 3.59 2.5 7.82 4.71 13.1 4.69 M23 M 1.68 16.63 18.19 18.63 13.32 4.69 M24 M 3.86 9.8 3.99 8.17 4.23 2.45 M25 M 9.03 1.71 4.07 4.58 6.1 2.24 M26 M 3.34 0.89 10.17 8.83 12.84 10.75 M27 M 3.9 5.73 12.03 6.84 19.44 3.5 M28 M 11.64 4.64 7.96 5.04 4.21 8.19 M29 M 5.50 5.73 7.40 8.40 10.50 4.58 M30 M 6.46 8.3 1.98 3.3 9.86 1.41 M31 M 1.26 4.31 5.87 6.1 7.27 1.43 M32 M 2.59 5.15 8.05 6.38 10.95 0.96 M33 M 5.01 8.6 3.21 6.26 5.78 2.36
Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual male subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
214
L VL R VL L VL R VL L MH R MH L MH R MH
180°/s 180°/s 240°/s 240°/s 0°/s 0°/s 60°/s 60°/s
4 .15 3.7 2.94 1.73 10.4 3.9 2.61 5.54 5.95 5.2 5.54 6.96 4.57 4.03 5.79 2.3 2.05 4.55 19.17 3.11 2.59 3.76 5.48 7.8 4.69 7.2 3.32 5.56 2.75 4.08 10.37 7.18 5.68 6.00 6.21 6.21 4.61 5.65 6.14 6.31 6.5 6.69 4.84 2.58 11.45 4.38 6.12 6.75
5.83 6.13 5.12 6.66 7.09 6.36 8.33 11.21 2.27 6.02 4.67 4.77 6.99 3.68 3.6 2.12 8.62 4.17 2.87 12.06 4.26 9.83 7.97 12.54 4.53 13.27 0.82 4.43 1.16 6.41 14.02 7.6 4.5 15.25 9.32 7.44 5.33 4.49 7.82 10.99
6.94 5.17 7.55 13.07 4.2 3.95 4.5 3.2 6.08 8.39 5.98 5.55 5.81 3.8 7.73 5.81 2.14 8.44 11.5 8.68 5.5 4.86 4.19 5.28 3.67 4.12 5.03 3.2 3.78 3.38 4.82 2.37 12.4 8.23 2.04 8.23 3.54 6.87 3.3 5.95 1.87 3.25 2.87 6.29 2.9 4.02 3.94 11.23 5.41 2.77 2.87 6.29 1.9 2.68 2.97 9.66 3.08 3.46 6.16 4.92 7.54 4.43 7.27 2.38 0.96 4.85 2.42 9 1.89 3.86 3.27 6.31
11.19 3.88 9.03 6.4 3.65 5.78 7.42 4.3 9.19 4.74 7.12 9.22 1.82 9.07 11.15 6.5 8.2 7.64 10.17 6.06 2.65 5.02 5.64 4.5
6.56 4.34 3.32 3.19 0.89 1.87 4.69 6.35 9.93 7.3 13.7 14.9 1.1 7.36 5.19 3.56 2.53 6.23 10.22 14.45 3.62 20 7.17 4.16 3.92 6.3 13.3 3.45 1.97 7.77 4.55 1.91 10.1 8.24 4.35 6.61 9.46 5.08 7.33 5.63 6.01 5.90 6.25 6.21 4.82 5.52 6.34 6.92 5.48 4.37 6.31 3.8 5.62 4.87 6.26 9.08 5.85 2.79 7.23 1.29 10.05 9.06 7.58 13.2 3.75 3 2.63 1.29 1.24 2.92 4.23 1.73 3.98 8.74 5.23 3.84 7.8 6.85 2.91 6.98
Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual male subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
215
L MH R MH L MH R MH L MH R MH L MV R MV
120°/s 120°/s 180°/s 180°/s 240°/s 240°/s 0°/s 0°/s
3 .85 13.7 3.72 4.85 6.88 4.55 1.71 2.7 8.14 3.95 4.43 6 8.87 10.16 1.06 5.07 8.32 2.71 5.03 3.71 4.31 4.34 7.41 1.71 8.39 2.64 2.54 5.65 9.3 3.83 2.87 3.77 7.16 4.85 19.89 5.88 6.39 6.42 4.34 6.24 6.02 6.85 4.83 7.92 8.68 3.4 4.27 2.54 6.57 5.68 2.15 2.97 3.26 4.42 7.5 6.19 3.54 1.5 1.3 2.08 4.35 2.25 5.35 6.03
10.31 7.9 5.24 13.64 10.55 6.99 5.45 3.96 3.82 7.11 3.29 10.02 4.97 4.62 8.52 3.02 9.42 4.17 3.47 3.57 3.83 9.04 7.27 10.83 5.97 4.27 5.49 1.05 6.87 4.79 1.5 6.34 2.27 2.74 1.92 3.45 5.09 3.13 3.19 5.69 6.81 2.52 9.66 7.33 4.96 7.01 2.63 2.45 3.27 8.06 4.8 6.24 5.95 9.52 3.5 12.68 4.54 5.11 16.73 2.74 17.97 12.57 4.5 11.11
13.81 1.83 2.21 4.65 0.87 1.78 6.46 3.76 6.22 1.83 3.24 6.06 5.55 4.92 6.46 9.65
12.94 5.61 5.95 9.03 4.01 3.71 5.69 8.44 4.6 1.73 3.19 6.12 6.54 6.98 5.96 11.36
9.07 6.55 4.94 6.01 5.52 1.07 2.36 10.39 5.43 2.28 1.62 9.41 8.69 3.51 2.36 5.1
17.25 10.49 5.32 1.77 10.5 21.52 4.83 7.67 5.49 1.79 2.53 4.69 2.2 5.06 3.83 7.66 5.8 1.12 5.78 2.75 3.27 4.32 1.52 3.6
2.37 1.89 5.03 4.16 5.27 4.71 3.79 2.76 4.77 2.39 13.43 10.84 5.16 6.06 3.05 8.34 6.96 4.33 4.85 6.08 3.43 6.24 4.35 2.82 6.95 4.85 4.70 5.80 6.30 6.45 4.36 6.24 11.3 9.13 4.51 4.5 4.4 7.31 1.14 6.35 6.81 7.44 4.73 12.29 17.65 18.01 4 7.51 4.54 3.86 6.57 6.19 3.69 8.81 7 8.32
13.13 6.95 7.85 8.09 4.21 4.98 3.15 1.89 Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual male subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
216
L MV R MV L MV R MV L MV R MV L MV MV 60°/s 60°/s 120°/s 120°/s 180°/s 180°/s 240°/s 240°/s
5 .7 6.22 11.2 4.24 2.39 4.66 7.76 8.95
5.02 4.92 8.87 5.6 4.21 3.9 6.53 11.5 1.41 8.02 9.2 8.22 3.36 4.76 5.41 9.89 3.02 12.29 13.68 8.12 3.63 10.29 11.08 5.51 8.50 8.78 8.82 4.61 6.32 9.61 9.87 10.01
11.19 8.96 13.33 6.69 7.69 10.01 11.77 3.63 9.86 5.59 7.14 1.86 6.85 9.71 9.37 3.12
17.17 16.38 13.8 4.03 2.01 6.71 7.22 3.84 9.22 5.52 14.5 5.91 5.2 4.8 5.21 22.1
11.44 7.71 10.39 6.66 3.68 8.19 11.13 6.19 7.38 7.78 7.9 1.18 6.09 14.1 10.37 7.79 5.05 12.42 6.8 6.45 3.27 13.82 9.62 15.27 2.99 1.93 4.46 1.36 5.17 9.61 6.94 10.46 6.29 4.11 9.32 1.31 16.87 20.77 21.53 16.29 8.85 14.26 5.15 2.89 8.31 6.68 11.21 10.79 9.16 7.3 4.82 4.87 2.97 5.18 6.88 6.23 9.66 5.45 4.41 2.58 11.51 10.21 9.45 4.68
10.35 9.85 7.73 2.58 7.92 13.06 13.95 10.43 10.18 6.37 7.29 6.99 6.26 8.67 14.3 3.37
8.9 7.68 6.98 4.11 2.11 15.39 19.94 13.57 11.42 5.4 8.33 3.77 13.94 6.82 8.96 9.22 6.84 5.5 4.54 9.76 7.79 8.18 17.65 13.72 5.46 13.04 13.26 1.1 1.11 9.4 19.54 21.19 8.47 12.67 3.16 1.3 8.65 8.52 12.97 9.76
10.38 9.01 22.68 4.47 6.88 2.52 5.12 9.34 16.79 9.02 15.62 5.84 3.22 14.38 11.11 26.59 3.36 5.47 10.62 6.25 16.43 21.58 7.93 7.77 6.93 11.26 11.31 1.5 14.64 17.54 7.26 13.22 8.05 8.36 8.40 5.12 6.41 9.03 9.87 9.89 1.93 10.97 7.03 7.02 10.31 18.27 6.13 10.63 20 12.21 2.47 4.46 3.75 4.09 4.9 5.12
6.21 8.94 4.32 5.66 3.95 12.39 6.2 5.94 11.03 11.57 4.15 2.22 6.12 5.32 10.05 10.69 Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual male subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
217
Muscles L VL R VL L VL R VL L VL R VL
Id. Speed 0°/s 0°/s 60°/s 60°/s 120°/s 120°/s
F1 F 4.65 6.3 6.8 4.32 10.88 2.99 F2 F 4.15 5.7 4.85 5.92 5.07 23.29 F3 F 1.26 7.12 3.85 6.19 3.78 11.38 F4 F 6.84 5.3 10.32 5.26 6.73 2.12 F5 F 2.36 7.22 6.54 7.55 9.08 4.65 F6 F 2.5 3.24 5.36 4.24 4.78 2.85 F7 F 3.95 7.47 7.54 8.37 7.03 0.82 F8 F 7.54 3.44 7.18 6.47 3.84 5.86 F9 F 5.2 3.89 1.35 3.53 19 0.82
F10 F 1.41 5.46 12.52 12.97 13.88 1.26 F11 F 5 5.83 8.82 8.05 3.9 4.24 F12 F 6.81 3.62 5.09 6.36 3.36 3.83 F13 F 2.87 6.84 5.8 12.55 6.15 2.77 F14 F 6.17 4.79 6.61 6.78 9.11 0.52 F15 F 8.52 4.64 7.96 4.21 5.04 2.5 F16 F 3.59 6.31 5.44 10.82 2.41 3.59 F17 F 1.5 2.2 3.55 3.98 12.6 3.59 F18 F 5.2 3.89 4.97 10.5 8.79 7.09 F19 F 1.41 3.56 8.14 6.42 4.73 2.45 F20 F 2.87 5.53 9.14 5.52 4.15 2.82 F21 F 7.57 10.97 13.88 8.26 5.93 1.58 F22 F 4.65 8.87 3.72 9.6 5.11 5.45
Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual female subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
218
L VL R VL L VL R VL L MH R MH L MH R MH
180°/s 180°/s 240°/s 240°/s 0°/s 0°/s 60°/s 60°/s 5 5.9 6.14 2.63 1.13 6 4.72 4.74
2.48 3.87 3.63 3.37 3.87 2.59 7.92 7.35 6.8 4.3 3.65 9.45 3.95 2.51 2.93 5.54
5.55 9.48 3.88 6.86 7.09 4.01 2.04 5.96 1.59 4.53 1.83 1.82 1.71 13.71 5.59 2.57 3.63 4.83 5.54 9.1 3.56 2.53 5.94 5.2 5.23 7.92 4.16 7.9 2.99 4.86 5.21 5.27 3.23 3.7 2.41 5.77 5.45 2.99 5.28 8.83 3.69 14.83 11.95 18.09 2.87 19.63 11.63 12.9 6.29 12.26 14.39 15.53 7.7 6.03 9.16 7 2.5 3.79 8.14 4.98 1.34 4.75 4.33 2.47
1.15 4.9 9.41 2.84 8.06 3.09 5.13 7.09 11.08 4.93 14.63 16.07 1.14 9.68 5.37 9.27
9.9 7.99 5.81 7.7 8.96 3.15 3.51 7.62 10.1 8.24 2.06 11.64 5.26 5.08 7.33 5.63 3.72 6.99 6.53 5.6 4.79 6.79 3.96 5.3 2.51 3.58 3.26 2.71 4.72 2.61 7.12 4.96 7.74 7.72 11.28 12.32 9 7.99 12.14 9.83 2.9 7.12 3.54 5.61 5.23 9.39 8.85 3.56 5.8 11.97 25.09 7.26 2.8 4.55 8.16 4.72
1.41 5.68 5.46 5.14 1.73 5.85 2.07 3.11 5.52 6.11 6.34 8.01 1.91 6.17 6.24 5.43
Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual female subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
219
L MH R MH L MH R MH L MH R MH L MV R MV
120°/s 120°/s 180°/s 180°/s 240°/s 240°/s 0°/s 0°/s
8 .28 2.22 2.87 2.08 4.76 2.16 2.99 6.19 6.44 5.68 6.58 4.39 5.91 9.71 7.63 4.3 8.04 1.5 4.02 12.6 6.42 11.81 5.68 8.47 2.98 6 5.59 6.96 4.57 3.5 1.45 4.74 3.58 5.23 5.52 4.04 5.9 7.38 9.4 9.21 2.6 1.26 2.51 1 4.89 10.54 5.61 17.08
3.55 4.93 3.19 1.88 3.42 1.95 2.63 4.93 2.27 2.7 2.59 4.39 8.43 5.02 6.26 6.27
16.08 4.2 23.55 21.58 10.38 15.04 3.77 3.41 5.3 3.56 4.77 8.5 5.09 2.58 3.28 20.13
3.76 8.6 5.59 3.17 5.62 6.26 4.55 3 13.4 1.47 12 4.83 4.84 6.26 1.58 8.16 6.86 5.48 9.17 4.35 4.16 4.32 2.94 6.75 3.94 2.18 3.84 7.75 3.32 13.96 2.19 4.99 6.96 1.5 4.85 6.08 3.43 6.24 7.41 2.82 4.67 9.47 6.02 3.66 6.85 4.7 5.03 3.54
12.42 1.29 2.08 3.23 12.9 0.57 5.38 10.94 4.69 6.45 4.05 2.98 3.29 2.49 2.31 5.34 6.1 3.29 6.03 6.41 3.66 4.54 5 2.78
2.64 6.35 5.93 5.84 4.1 3.9 2.84 8.97 3.49 7.8 3.26 6.35 9.21 4.85 4.62 7.3
12.43 2.38 8.54 5.52 3.23 3.69 1.21 7.24 Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual female subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
220
L MV R MV L MV R MV L MV R MV L MV MV 60°/s 60°/s 120°/s 120°/s 180°/s 180°/s 240°/s 240°/s
6 .19 7.33 7.1 3.3 1.5 5.86 4.21 1.15 3.39 5.15 4.66 12.73 7.94 6.65 3.51 5.68 3.67 8.69 8 6.7 8.32 11.08 9.29 9.07
16.37 8.46 6.75 6.05 2.05 6.8 19.38 7.55 8.89 5.74 19.19 6.13 8.56 6.81 5.36 12.04
11.99 11.23 12.36 3.58 9.68 11.6 11.82 11.3 5.14 4.64 3.4 2.16 2.92 11.04 5.39 1.89 8.24 4.06 9.46 4.49 8.87 7.28 8.06 9.88 8.75 8.96 2.6 3.03 6.43 13.22 3.96 20.35 1.72 10.39 11.3 4.46 12.88 6.42 7.77 11.58 7.03 11.74 6.99 7.51 8.27 10.62 9.25 7.99
13.11 3.01 5.06 1.18 6.6 10.75 10.66 9.69 14.75 8.96 6.74 1.5 5.72 8.38 11.52 18.31 11.24 14.85 13.84 4.09 13.23 9.88 5.25 12.77 6.93 11.26 11.31 5.1 14.64 17.54 7.26 13.22 6.78 11.55 7.94 5.38 7.37 6.12 11.97 4.34 10.1 2.93 2.95 2.16 11.96 13.03 6.27 2.49 6.94 7.42 7.19 5.85 4.02 9.48 12.96 15.17 1.22 4.49 8.37 1.86 10.76 8.94 9.08 8.96 1.87 9.52 15.66 6.66 5.94 12.43 17.3 10.6
14.53 3.5 3.54 5.12 3.62 3.57 8.22 2.04 2.62 11.9 3.43 1.41 7.24 4.25 12.75 4.12
Table 3A.2
BTSD of EMG MF resul ts in % for ind iv idual female subjects of Study One
BTSD=Between t r ia ls s tandard devia t ion L=Lef t R=Right VL = Vastus la tera l is MH=Media l hamstr ings VM=Vastus media l is
0°/s 60°/s 120°/s 180°/s 240°/s VL 0.98 0.81 0.91 0.63 0.90 MH 0.92 0.78 0.57 0.83 0.33 VM 0.99 0.96 0.40 0.36 0.47
T ab le 3A .3 p va lu es f o r t he b i l a t e ra l d i f f e r enc e o f EM G M F o f t he v as t us l a te ra l i s (VL ) , med i a l ha ms t r i n gs (M H ) , a nd v as t us m e d ia l i s (V M) a t va r i o us s pe eds
221
0
10
20
30
40
50
60
70
80
0°/sec 60°/sec 120°/sec 180°/sec 240°/sec
Med
ian
Freq
uenc
y in
Hz
Left
Right
F ig 3A.1 Vas tus la tera l i s
0
10
20
30
40
50
60
70
80
0°/sec 60°/sec 120°/sec 180°/sec 240°/sec
Med
ian
Freq
uenc
y in
Hz
Left
Right
F ig 3A.2 Med ia l hamst r ings
010
2030
405060
7080
90100
0°/sec 60°/sec 120°/sec 180°/sec 240°/sec
Med
ian
Freq
uenc
y in
Hz
LeftRight
F ig 3A.3 Vas tus med ia l i s
Figures 3A.1 to 3A.3 EMG median frequency of the VL, MH and VM of al l subjects
222
0
10
20
30
40
50
60
70
80
90
VL MH VMMuscles
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right
0
10
20
30
40
50
60
70
80
90
100
VL MH VM
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right
F i g 3A .4 0 ° / s econ d F ig 3A .5 6 0 ° / seco nd
0
10
20
30
40
50
60
70
80
VL MH VM
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right
0
10
20
30
40
50
60
70
80
VL MH VM
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right
F i g 3A .7 180 ° / s eco nd F ig 3A .6 12 0° / seco nd
0
10
20
30
40
50
60
70
80
90
VL MH VM
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right
F i g 3A .8 2 40 ° / sec on d
F igures 3A.4 to 3 .8 EMG median f requency o f VL, MH and VM of ma le and female sub jec ts measured a t 0° , 60° , 120° , 180° and 240° /second
223
0
10
20
30
40
50
60
70
80
0°/sec 60°/sec 120°/sec 180°/sec 240°/sec
Speeds
Med
ian
Freq
uenc
y in
Hz
LeftRight
F ig 3A.9 EMG median f requency o f vas tus la tera l i s in ma le sub jec ts a t d i f fe rent speeds
0
10
20
30
40
50
60
70
80
0°/sec 60°/sec 120°/sec 180°/sec 240°/secSpeeds
Med
ian
Freq
uenc
y in
Hz
LeftRight
F ig 3A.10 EMG median f requency o f vas tus la te ra l i s in female sub jec ts a t d i f fe rent speeds
224
0
10
20
30
40
50
60
70
80
90
0°/sec 60°/sec 120°/sec 180°/sec 240°/secSpeed
Med
ian
Freq
uenc
y in
Hz
LeftRight
F ig 3A.11 EMG median f requency o f med ia l hamst r ings in ma le sub jec ts a t d i f fe rent speeds
0
10
20
30
40
50
60
70
80
0°/sec 60°/sec 120°/sec 180°/sec 240°/secSpeeds
Med
ian
Freq
uenc
y in
Hz
LeftRight
F ig 3A.12 EMG med ian f requency o f media l hamst r ings in fema le sub jec ts a t d i f fe rent speeds
225
0
10
20
30
40
50
60
70
80
90
100
0°/sec 60°/sec 120°/sec 180°/sec 240°/sec
Speeds
Med
ian
Freq
uenc
y in
Hz
LeftRight
F ig 3A.13 EMG median f requency o f vas tus media l is in ma le sub jec ts a t d i f fe rent speeds
0
10
20
30
40
50
60
70
80
90
100
0°/sec 60°/sec 120°/sec 180°/sec 240°/secSpeeds
Med
ian
Freq
uenc
y in
Hz
LeftRight
F ig 3A.14 EMG med ian f requency o f vas tus med ia l i s in female sub jec ts a t
d i f fe rent speeds
226
0
1
2
3
4
5
6
VL MH MV
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right 0
1
2
3
4
5
6
7
8
VL MH MV
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right
F i g 3A .1 5 0 ° / seco nd F ig 3A .1 6 6 0 ° / seco nd
0
1
2
3
4
5
6
7
8
9
10
VL MH MV
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right0
1
2
3
4
5
6
7
8
9
10
VL MH MV
Med
ian
Freq
uenc
y in
Hz
M LeftM RightF LeftF Right
F i g 3A .1 7 1 20 ° / sec on d F ig 3A .1 8 1 80 ° / sec on d
0
2
4
6
8
10
VL MH MV
Med
ian
Freq
uenc
y in
Hz
M Left
M Right
F Left
F Right
F i g 3A . 19 2 40 ° / sec on d
F igures 3A.15 to 3A.19 Between t r ia l s s tandard dev ia t ion o f med ian f requency o f VL, MH and VM of male and fema le sub jec ts measured a t 0° /s , 60° /s , 120° /s , 180° /s and 240° /s respec t ive l y
227
0
2
4
6
8
10
12
A B C D E F G H I J K L
ACL reconstructed subjects
Isom
etric
Str
engt
h
Uninvolved ACLR
Fig 5A.1 I somet r ic s t rength o f the quadr iceps o f the un invo lved and ACL reconst ruc ted l imbs
0
2
4
6
8
10
12
A B C D E F G H I J K LACL reconstruction subjects
Isom
etric
Str
engt
h
Uninvolved ACLR
Fig 5A.2 Isomet r ic s t rength o f the hamst r ings o f the un invo lved and ACL reconst ruc ted l imbs
228
-40
0
40
-40 -30 -20 -10 0 10 20 30 40
EMG Median Frequency Shift
Bila
tera
l ext
ensi
on T
trqu
e in
%
Fig 5A.3 Cor re la t ion be tween med ian f requency sh i f t o f the vas tus la tera l i s and the b i la tera l d i f f e rence o f the extens ion to rque in ACL reconst ruc ted sub jec ts
-45
55
-50 50
EMG Median Frequency Shift
Bila
tera
l fle
xion
torq
ue d
iffer
ence
in %
Fig 5A.4 Cor re la t ion be tween med ian f requency sh i f t o f the vas tus la tera l i s and the b i la tera l d i f f e rence o f the f lex ion to rque in ACL recons t ruc ted sub jec ts
229
-35
-60 40
EMG median frequency shift
% B
ilate
ral e
xten
sion
torq
ue d
iffer
ence
Fig 5A.5 Cor re la t ion between median f requency sh i f t o f the med ia l hamst r ings and the b i la tera l d i f f e rence o f the extens ion to rque in ACL reconst ruc ted sub jec ts
-50
50
-60 -40 -20 0 20 40 60
EMG median frequency shift
Bila
tera
l fle
xion
torq
ue d
iffer
ence
%
Fig 5A.6 Cor re la t ion between med ian f requency sh i f t o f the med ia l hamst r ings and the b i la te ra l d i f f e rence o f the f lex ion to rque in ACL reconst ruc ted sub jec ts
230
-35
-50 0 50
EMG median frequency shift
% B
ilate
ral e
xten
sion
torq
ue d
iffer
ence
F ig 5A.7 Cor re la t ion between med ian f requency sh i f t o f the vas tus media l i s and the b i la tera l d i f f e rence o f the extens ion to rque in ACL reconst ruc ted sub jec ts
-45
-50 50
EMG median frequency shift
Bila
tera
l fle
xion
torq
ue d
iffer
ence
in %
F ig 5A.8 Cor re la t ion be tween median f requency sh i f t o f the vas tus media l i s and the b i la tera l d i f f e rence o f the f lex ion to rque in ACL recons t ruc ted sub jec ts
231
MFBD of VL vs Cincinnati Score (n=12)
50
60
70
80
90
100
0 10 20 30 40 5% Bilateral Discrepancy
Func
tiona
l Sco
re
0
F ig 5A.9
MFBD of MH vs Cincinnati Score (n=12)
50
60
70
80
90
100
110
0 10 20 30 40% Bilateral Discrepancy
Fun
ctio
nal S
core
50
F ig 5A.10
MFBD of VM vs Cincinnati Score (n=12)
50
60
70
80
90
100
110
0 10 20 30 40% Bilateral Discrepancy
Func
tiona
l Sco
re
50
F ig 5A.11
F igures 5A.9-5A.11 show the cor re la t ion between the percentage b i la tera l d i sc repancy o f the med ian f requency (MFBD) o f VL, MH and VM and C inc innat i func t iona l score in ACL reconst ruc ted sub jec ts
232
0
20
40
60
80
100
120
12 17 22 27 32 37 42
Age
Func
tiona
l Sco
re
Fig 5A.12 Cor re la t ion between age and C inc innat i func t iona l score in ACL recons t ruc ted sub jec ts
0
20
40
60
80
100
120
6 8 10 12 14 16
Post operative months
Func
tiona
l Sco
re
F ig 5A.13 Cor re la t ion between pos t opera t ive months and Cinc innat i func t iona l score in ACL reconst ruc ted sub jec ts
233
Statistical Information for Study One
The between trials standard deviation (BTSD) values
Descriptive BTSD
N Mean
Std . Dev ia t i
on Std .
Er ror 95% Conf idence In terva l fo r Mean Min i Max i
Lower Bound
Upper Bound
1 .00 330 5.3109 3 .00962 .16567 4.9850 5.6368 .89 20.132.00 330 7.3287 4 .67567 .25739 6.8224 7.8350 1 .22 66.603.00 330 6.3681 5 .32888 .29335 5.7910 6.9452 .52 72.604.00 330 6.6572 3 .92801 .21623 6.2318 7.0826 .96 23.555.00 330 7.5765 4 .56269 .25117 7.0824 8.0706 .57 26.59Tota l 1650 6.6483 4 .43906 .10928 6.4339 6.8626 .52 72.60
ANOVA BTSD
Sum of Squares d f
Mean Square F S ig .
Between Groups 1053.318 4 263.329 13.778 .000
Wi th in Groups 31440.575 1645 19.113 Tota l 32493.892 1649
Post Hoc Tests Mul t ip le Compar isons
234
Dependent Var iab le : BTSD Tukey HSD
( I ) SPEED
(J ) SPEED
Mean Di f fe renc
e ( I - J ) S td .
Er ror S ig . 95% Conf idence In terva l
Lower Bound
Upper Bound
1 .00 2 .00 -2 .0178( * ) .34035 .000 -2 .9472 -1 .0884 3 .00 -1 .0572( * ) .34035 .016 -1 .9866 - .1278 4 .00 -1 .3463( * ) .34035 .001 -2 .2758 - .4169 5 .00 -2 .2657( * ) .34035 .000 -3 .1951 -1 .33622.00 1 .00 2 .0178( * ) .34035 .000 1.0884 2 .9472 3 .00 .9606( * ) .34035 .039 .0312 1 .8900 4 .00 .6715 .34035 .280 - .2579 1 .6009 5 .00 - .2478 .34035 .950 -1 .1773 .68163.00 1 .00 1 .0572( * ) .34035 .016 .1278 1 .9866 2 .00 - .9606(* ) .34035 .039 -1 .8900 - .0312 4 .00 - .2891 .34035 .915 -1 .2185 .6403 5 .00 -1 .2085( * ) .34035 .004 -2 .1379 - .27904.00 1 .00 1 .3463( * ) .34035 .001 .4169 2 .2758 2 .00 - .6715 .34035 .280 -1 .6009 .2579 3 .00 .2891 .34035 .915 - .6403 1 .2185 5 .00 - .9193 .34035 .054 -1 .8488 .01015.00 1 .00 2 .2657( * ) .34035 .000 1.3362 3 .1951 2 .00 .2478 .34035 .950 - .6816 1 .1773 3 .00 1 .2085( * ) .34035 .004 .2790 2 .1379 4 .00 .9193 .34035 .054 - .0101 1 .8488
* The mean d i f f e rence i s s ign i f i cant a t t he .05 leve l .
Homogeneous Subsets BTSD Tukey HSD
Subset fo r a lpha = .05 SPEED N 1 2 3 1 .00 330 5 .3109 3 .00 330 6 .3681 4 .00 330 6 .6572 6.65722.00 330 7 .32875.00 330 7 .5765Sig . 1 .000 .915 .054
Means for g roups in homogeneous subsets are d isp layed . Uses Harmonic Mean Sample S ize = 330.000.
235
The percentage bilateral discrepancy (%BD) values Descriptive %BD
N Mean Std .
Dev ia t ion Std .
Er ror 95% Conf idence In terva l fo r Mean Min Max
Lower Bound
Upper Bound
1 .00 165 4 .0158 3 .05726 .23801 3.5458 4.4857 .00 15.90
2.00 165 6 .7485 5 .06064 .39397 5.9706 7.5264 .00 34.10
3.00 165
12.6630 9 .06348 .70559 11.2698 14.0562 .00 45.30
4.00 165
19.2000 12.56556 .97823 17.2685 21.1315 .30 59.90
5.00 165
23.8030 13.75987 1.07120 21.6878 25.9181 1 .77 63.07
Tota l 825
13.2860 12.14131 .42271 12.4563 14.1158 .00 63.07
ANOVA %BD
Sum o f
Squares d f Mean
Square F S ig . Between Groups 45316.700 4 11329.175 121.995 .000
Wi th in Groups 76150.278 820 92.866 Tota l 121466.97
8 824
236
Post Hoc Tests Mul t ip le Compar isons Dependent Var iab le : %BD Tukey HSD
( I ) SPEED
(J ) SPEED
Mean Di f fe rence
( I -J ) S td .
Er ror S ig . 95% Conf idence
In terva l
Lower Bound
Upper Bound
1 .00 2 .00 -2 .7327 1.06097 .076 -5 .6333 .1678 3 .00 -8 .6473( * ) 1 .06097 .000 -11.5478 -5 .7467 4 .00 -15 .1842( * ) 1 .06097 .000 -18.0848 -12 .2837 5 .00 -19 .7872( * ) 1 .06097 .000 -22.6877 -16 .88672.00 1 .00 2 .7327 1.06097 .076 - .1678 5 .6333 3 .00 -5 .9145( * ) 1 .06097 .000 -8 .8151 -3 .0140 4 .00 -12 .4515( * ) 1 .06097 .000 -15.3520 -9 .5510 5 .00 -17 .0545( * ) 1 .06097 .000 -19.9550 -14 .15403.00 1 .00 8 .6473( * ) 1 .06097 .000 5.7467 11.5478 2 .00 5 .9145( * ) 1 .06097 .000 3.0140 8 .8151 4 .00 -6 .5370( * ) 1 .06097 .000 -9 .4375 -3 .6364 5 .00 -11 .1399( * ) 1 .06097 .000 -14.0405 -8 .23944.00 1 .00 15.1842( * ) 1 .06097 .000 12.2837 18.0848 2 .00 12.4515( * ) 1 .06097 .000 9.5510 15.3520 3 .00 6 .5370( * ) 1 .06097 .000 3.6364 9 .4375 5 .00 -4 .6030( * ) 1 .06097 .000 -7 .5035 -1 .70245.00 1 .00 19.7872( * ) 1 .06097 .000 16.8867 22.6877 2 .00 17.0545( * ) 1 .06097 .000 14.1540 19.9550 3 .00 11.1399( * ) 1 .06097 .000 8.2394 14.0405 4 .00 4 .6030( * ) 1 .06097 .000 1.7024 7 .5035
* The mean d i f fe rence i s s ign i f i cant a t the .05 leve l .
Homogeneous Subsets %BD Tukey HSD
Subset fo r a lpha = .05 SPEED N 1 2 3 4 1 .00 165 4 .0158 2 .00 165 6 .7485 3 .00 165 12 .6630 4 .00 165 19 .2000 5 .00 165 23 .8030 S ig . .076 1.000 1.000 1.000
Means for g roups in homogeneous subsets are d isp layed . Uses Harmonic Mean Sample S ize = 165.000.
237
Appendix B
Ethical Approvals
238
239
240
QUTMEMORANDUM
To Mr Che T in Raymond L i , S tuden t , Schoo l o f Human Movement S tud ies From Secre ta ry , Un ivers i t y Human Research Eth ics Commi t tee Copy Pro f Tony Parker , Schoo l o f Human Movement S tud ies Date 2 May 2000
Sub jec t Cond i t iona l Approva l -1905H
I wr i te fu r ther to in format ion you prov ided in regard to cond i t iona l approva l awarded to your pro jec t , 'Muscu lar adapt ion in response to rehab i l i t a t ion fo l lowing an ter io r c ruc ia te l i gament in ju ry ' (OUT Ref No: 1905H) .
The Cha i rperson o f the Un ivers i t y Human Research Eth ics Commi t tee (UHREC) has cons idered your response and asked tha t I respond on her beha l f . The Cha i rperson has dec ided, under execut ive powers , tha t your response has addressed the Commi t tee 's reques ts I concerns .
Th is dec is ion i s sub jec t to ra t i f i ca t ion a t the 13 June 2000 meet ing o f the Commi t tee . However , you a re author ised to p roceed wi th your p ro jec t on th is bas is .
P lease do not hes i ta te to contac t me i f you have any fu r ther quer ies in re la t ion to th is mat te r .
l : :n
Secre tar ia t Phone: 2902 Facs im i le : 1818 Emai l : gx .a l len@qut .edu.au ht tp : l lwww .gu t .edu .au /draa/o r /e th ics . h tml
241
Appendix C
Subject recruitment information materials for
Studies One, Two and Three
242
Subject Recruitment Information
(Exper iment one)
We are conduct ing a study to evaluate the muscular adaptat ion in response to rehabi l i tat ion fo l lowing anter ior cruciate l igament in jury. At th is stage, we are recrui t ing pat ients wi th anter ior cruciate l igament (ACL) in jury or reconstruct ion to be involved in th is research project . Your involvement would take up approximately 1.5 hours of your t ime in two vis i ts at the School of Human Movement Studies, QUT, 'A' Wing, 'O' Block, Kelvin Grove. The ul t imate goal of th is study is to develop an ef fect ive rehabi l i tat ion program for ACL in jury or reconstruct ion. Much valuable informat ion wi l l be added to the current body of knowledge in the area of ACL rehabi l i ta t ion, which wi l l be of benef i t to you. The resul ts of the study have the potent ia l to enhance the therapeut ic processes involved in the management of ACL def ic ient knees including more ef fect ive and t imely rehabi l i ta t ion fo l lowing this in jury and ear l ier return to sports , work or act iv i t ies of dai ly l iv ing. You are qual i f ied to part ic ipate in th is s tudy i f you are:
• Male or female • No other previous medical record of other lesions to ei ther
knee, such as surgery, or torn cart i lage; • Not current ly receiving regular weight t ra ining regime to the
lower l imbs • No adverse ef fects for exercise training or test ing; and , • Aged between 15-55
243
Subject Recruitment Information
(Exper iment two)
We are conduct ing a study to evaluate the muscular adaptat ion in response to rehabi l i tat ion fo l lowing anter ior cruciate l igament in jury. At th is stage, we are recrui t ing normal subjects to be involved in th is research project as a control . Your involvement would take up approximately one hour of you t ime in two vis i t and another 15 - 30 minutes of your t ime in 12 vis i ts over a per iod of 4 weeks at the School of Human Movement Studies, QUT, Kelv in Grove. The goal of th is study is to develop an ef fect ive rehabi l i tat ion program for ACL in jury or reconstruct ion. Much valuable informat ion wi l l be added to the current body of knowledge in the area of ACL rehabi l i ta t ion, which wi l l be of benef i t to the ACL in jured pat ient . The resul ts of the study have the potent ia l to enhance the therapeut ic processes involved in the management of ACL def ic ient knees including more ef fect ive and t imely rehabi l i ta t ion fol lowing this in jury and ear l ier return to sports , work or act iv i t ies of dai ly l iv ing. You are qual i f ied to part ic ipate in th is s tudy i f you are:
• Male • No other previous medical record of other lesions to ei ther
knee, such as surgery, or torn cart i lage; • Not current ly receiving regular weight t ra ining regime to the
lower l imbs • No adverse ef fects for exercise training or test ing; and • Aged between 15-55
244
Subject Recruitment Information
(Exper iment three)
We are conduct ing a study to evaluate the muscular adaptat ion in response to rehabi l i tat ion fo l lowing anter ior cruciate l igament in jury. At th is stage, we are recrui t ing pat ients wi th anter ior cruciate l igament (ACL) in jury or reconstruct ion to be involved in th is research project . The goal of th is study is to develop an ef fect ive rehabi l i tat ion program for ACL in jury or reconstruct ion. Much valuable informat ion wi l l be added to the current body of knowledge in the area of ACL rehabi l i ta t ion, which wi l l be of benef i t to you. The resul ts of the study have the potent ia l to enhance the therapeut ic processes involved in the management of ACL def ic ient knees including more ef fect ive and t imely rehabi l i tat ion fo l lowing th is in jury and ear l ier re turn to sports, work or act iv i t ies of dai ly l iv ing. You are qual i f ied to part ic ipate in th is s tudy i f you are:
• Male • Cl in ical ly conf i rmed ruptured of ACL 3 -9 months ear l ier ; or
having an ACL reconstruct ion 6 - 12 months ear l ier • No other previous medical record of other lesions to ei ther
knee, such as surgery, or torn cart i lage; • Not current ly receiving regular weight t ra ining regime to the
lower l imbs • No adverse ef fects for exercise training or test ing; and, • Aged between 15-40
245
Dear Further to our recent te lephone conversat ion, please f ind at tached detai ls of the ACL Rehabi l i tat ion Research in accompanying subject informat ion package. The appointment for your f i rs t v is i t has been made for / /2000 a t : am/pm. For th is v is i t , p lease meet in Room A212, "A" Wing, " O" Block, School of Human Movement Studies, Queensland Universi ty of Technology, Herston Road, Kelvin Grove. (Please see the at tached map). Please use the pay and display car park. (We shal l re imburse to you). "A" Wing is direct ly in f ront of the car park and I shal l be wait ing for you in f ront of the bui ld ing. (Marked X on the at tached map) Dur ing this v is i t , I wi l l explain detai ls of the exper iment, and conduct a basic examinat ion for your sui tabi l i ty of part ic ipat ion. For ease of examinat ion, I would be grateful i f you could br ing a pair of shorts. I f you are happy to part ic ipate fo l lowing the examinat ion, you wi l l need to s ign a consent form for your acceptance into th is project before you leave. There will not be any test ing or exercise for th is v is i t , which wi l l last for 30-40 minutes. Meanwhi le, should you have any quer ies, please do not hesi tate to contact me. I would l ike to take this opportuni ty to thank you for showing interest in th is research. I appreciate very much your assistance, which wi l l certainly contr ibute to the success of th is research. Yours Sincerely, C. T. (Raymond) Li Ph.D. s tudent, Room A 321, A Wing, O Block, School of Human Movement Studies, Queensland Universi ty of Technology (Kelv in Grove) Ph: 3864 5843 (W), 3423 7597(H), 0403 125 882 (Mobi le)
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Dear Further to our recent te lephone conversat ion, please f ind at tached some detai ls of the ACL Rehabi l i tat ion Research. I shal l contact you later to see i f you are interested in part ic ipat ing in th is research project and to arrange the t ime for your f i rst v is i t . Meanwhi le, should you have any quer ies, please do not hesi tate to contact me. I would l ike to take this opportuni ty to thank you for showing interest in th is research. I appreciate very much your assistance, which wi l l certainly contr ibute to the success of th is research. Yours Sincerely, C. T. (Raymond) Li Ph.D. s tudent, Room A 321, A Wing, O Block, School of Human Movement Studies, Queensland Universi ty of Technology (Kelv in Grove) Ph: 3864 5843 (W), 3423 7597(H), 0403 125 882 (Mobi le)
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Appendix D
Consent forms for
Studies One, Two and Three
approved by the UHREC, QUT
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Consent Form
Chief Investigator: Name: Che Tin Raymond Li School Human Movement Studies, QUT Phone: (w) 3864 5843; (h) 3423 7597 Project Tit le: Muscular Adaptation in Response to
Rehabil i tation Following Anterior cruciate Ligament Injury.
The invest igator(s) conduct ing this research project abides by the pr inciples governing the ethical conduct of research and, at a l l t ime, avows to protect the interests, comfort and safety of a l l subjects. This form and the accompanying Subject Informat ion Package have been given to you for your protect ion. They contain an out l ine of the exper imental procedures and possible r isks. Your s ignature below wi l l indicate that : 1. you have received the Subjects Informat ion Package and that you
have read i ts contents; 2. you clear ly understand the procedures and the possible r isks
involved; and that you have been given the opportuni ty to discuss the contents of the Subject Informat ion Package wi th one of the invest igators pr ior to the commencement of the exper iment ;
3. you understand that al l data which you have provided wi l l only be
revealed to the invest igators and yoursel f . When resul ts of th is study are publ ished you wi l l remain anonymous;
4. your part ic ipat ion is voluntary and therefore may be terminated at
any moment by you without comment and penalty, and without jeopardiz ing your involvement wi th the Queensland Universi ty of Technology and /or your Universi ty course assessment;
5. you may direct any inquir ies and further quest ions to Che Tin
Raymond Li at the QUT-School of Human Movement Studies on 3864 5843. You may also direct complaints and concerns regarding the ethical conduct of th is invest igat ion to the Secretary of Queensland Universi ty of Technology Research Commit tee, on 3864 2902;
6. you wi l l receive feedback on your resul ts at the t ime of the study,
and
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7. you agree to part ic ipate in the exper iment procedures set out in the Subject Informat ion Package for the research project ent i t led" Muscular Adaptation in Response to Rehabil i tat ion Following Anterior cruciate Ligament Injury" as a part of a postgraduate thesis for a Doctor of Phi losophy for Che Tin Raymond Li
I voluntar i ly give my consent to part ic ipate in th is research study. I understand I wi l l receive a copy of th is consent form. _______________________ _________________________ Subject Name (please pr int ) Signature ___________________________ _________________________ Invest igator Name (please Pr int) Signature _______________________ Date
Name and Phone no. of person to contact in case of an emergency ___________________________ __________________ Name (please pr int) Phone Number
Appendix E
The Cincinnati Rating System Scoring Sheet
(Modified)
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The Cincinnati Rating System Scoring Sheet Name:_______________________________ Ref. No.:___________ Sex ____ Age: _____ Date of Assessment: _____________________ Diagnosis:_______________________________________________ Contact No: (W)___________(H)____________(Mobi le)___________ Score: Part I Sub-total-- --- - --- --- --- -- - --- --- --- -- - Part I I Sub-total- --- --- --- --- -- - --- --- --- -- - --- Total - - --- --- --- --- -- - --- --- --- -- - --- --- --- -- - --- This quest ionnai re consis ts of two par ts . Par t I (page 1) consis ts o f 3 quest ions which assess the symptoms of your involved knee. Par t I I (page 2) consis ts of 5 quest ions which assess the func t iona l ab i l i ty o f your involved knee. P lease c i rc le the most appropr ia te score. Thank you very much. Raymond C. T. L i Ph.D. Student School o f Human Movement Studies, QUT (w) 3864 5843 (H) 3376 0882 (Mobi le) 0403 125 882
--
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- - -
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The Cincinnati Rating System Scoring Sheet Name:_____________________________ Ref. No.:_____________
Points
Part I : Symptoms 1. Pain
20 No Pa in , no rma l knee , pe r fo rm 100%.
16 Occas iona l pa in w i th s t renuous spor ts , some l im i ta t ions bu t to le rab le .
12 Occas iona l pa in w i th l i gh t rec rea t iona l spor ts , b rough t on by ac t i v i t i es such as runn ing .
8 Pa in , b rough t on b y l i gh t rec rea t iona l ac t i v i t i es . Occas iona l occurs w i th wa lk ing .
4 Pa in i s a s i gn i f i can t p rob lem wi th s imp le ac t i v i t i es such as wa lk ing . Re l ieved by res t .
0 Pa in pe rs i s t a l l t he t ime , occurs w i th s tand ing . No t re l i eved wi th res t .
2 . Swe l l i ng
10 No swe l l i ng , no rma l knee , 100% ac t i v i t y .
8 Occas iona l swe l l i ng w i th s t renuous spor ts , some l im i ta t i ons bu t to le rab le .
6 Occas iona l swe l l i ng w i th l i gh t spo r ts , b rou gh t on by ac t i v i t i es such as runn ing .
4 Swe l l i ng , l im i t s spor ts . Occurs w i th s imp le wa lk ing ac t i v i t i es (abou t 3 t imes /yea r ) .
2 Swe l l i ng b rough t on by s imp le wa lk i ng ac t i v i t i es and l i gh t work . Re l ieved wi th res t .
0 Severe p rob lem a l l o f the t i me , w i th s imp le ac t i v i t i es .
3 . G iv ing way
20 No g iv ing -way, no rma l knee , 100% ac t i v i t y .
16 Occas iona l g i v ing -way wi th s t renuous spo r ts , can pa r t i c ipa te w i th some guard ing .
12 Occas iona l g i v ing -wa y wi th l i gh t rec rea t iona l spor ts , ab le to compensa te , no t ab le to cu t o r tw i s t sudden l y .
8 G iv ing way l im i t s spor ts . Occurs w i th wa lk ing o r l i gh t wo rk (abou t 3 t imes /yea r ) .
4 G iv ing -way wi th s imp le wa lk ing ac t i v i t i es . B rough t on by s imp le wa lk ing ac t i v i t i es Re l ieved wi th res t .
0 Severe p rob lem a l l o f the t ime , w i th s imp le wa lk ing ac t i v i t i es , canno t tu rn o r tw i s t
Part I (Symptom) Sub-total
. . . /2
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The Cincinnati Rating System Scoring Sheet (cont inue) Name:_______________________________ Ref . No. :_________________
Points
Part I I : Funct ion
1 . Overa l l ac t i v i t y l eve l
20 No l im i ta t i on , no rma l knee , ab le to do eve ry th ing i nc lud ing s t renuous spor ts .
16 Per fo rm v igo rous spo r ts , bu t a t a l ower pe r fo rmance leve l and wi th gua rd ing .
12 L igh t rec rea t iona l ac t i v i t i es poss ib le , more s t renuous ac t i v i t i es cause p rob lem.
8 No spor ts ac t i v i t i es poss ib le . Wa lk ing ac t i v i t i es poss ib le w i th ra re symptoms.
4 Wa lk ing , ac t i v i t i es o f da i l y l i v ing cause modera te symptoms , f requen t l im i ta t i on .
0 Wa lk ing , ac t i v i t i es o f da i l y l i v ing c ause severe p rob lem, pe rs i s ten t symp toms. 2 . Wa lk ing
10 Norma l , un l im i ted . 8 S l igh t / m i ld p rob lem. 6 Modera te p rob lem: smoo th su r face up to 800m. 4 Sever p rob lem: on l y 2 -3 b locks . 2 Severe p rob lem: requ i res cane o r c ru tch . 3 . S ta i r s
10 Norma l , un l im i ted . 8 S l igh t / m i ld p rob lem. 6 Modera te p rob lem: on l y 10 -15 s teps . 4 Sever p rob lem: requ i res ban is te r , suppor t . 2 Severe p rob lem: on l y 1 -5 s teps . 4 . Runn ing
5 Norma l , un l im i ted : fu l l y compe t i t i ve , s t renuous . 4 S l igh t / m i ld p rob lem: run ha l f speed .
3 Modera te p rob lem: on l y 2 -4 km. 2 Sever p rob lem: on l y 1 -2 b lock . 1 Severe p rob lem: on l y a few s teps . 5 . Jump ing o r tw i s t i ng ac t i v i t i es
5 Norma l , un l im i ted : fu l l y compe t i t i ve , s t renuous . 4 S l igh t / m i ld p rob lem: some guard ing , bu t spo r ts poss ib le . 3 Modera te p rob lem: rec rea t iona l spor ts poss ib le . 2 Severe p rob lem: a f fec ts a l l spor ts , mus t cons tan t l y gua rd . 1 Severe p rob lem: on l y l i gh t ac t i v i t y poss ib le (go l f , swimming) .
Part I I ( function) Sub-total
- End -
Appendix F
Other information
1. The PAR-Q form
2. Out l ine of ACL rehabi l i tat ion program used by the Holy
Tr in i ty Hospi ta l
3. Resul ts of the Window pi lot study
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ACL REHABILITATION PROGRAMME USED BY THE HOLY TRINITY HOSPITAL
OUTLINE OF PRINCIPLES
Day 1 Surgery Day 2 Home Spl int , can take of f for exercises. Anter ior Cruciate Crutches, touch weight is al lowed. . At 1 week Gent le exercises, cal f movement. L igament Progress weight bear ing . At 2 weeks REVIEW by Dr Myers (wi th physio) Reconstruct ion .Spl int of f , 90° bend, Ful l weight as tolerated. .Co-contract ion, Leg raise wi th no resistance. . I t var ies as to how long i t takes to be able to walk wi thout a l imp. At 3 weeks Aim to be walking independent ly. . At 4 weeks Begin wi th your regular Physio. .Aim for 0 -1000 bending, fu l l weight bear ing .Quads and hamstr ing biofeedback/ s t imulat ion .hangs i f not st raight, 10 cm step ups, Cal f Pat ients of . .Part ia l squats (450) bi lateral . .Bike (no tension), gent le wobble board, At 6 week Add swimming (gent ly) , no f l ick ing. Dr Peter T Myers At 10 weeks Progress exercises & add resistance. Al l quadr iceps exercises must be closed chain, increase al l exercises, . .Add mini - t ramp, wobble board, lunges and sl ide board. l igament At 4 months Begin dynamic act iv i ty. . Increase speed and agi l i ty of some of the exercises. .Graduate al l exercises to develop good strength. . I f a l l e lse is wel l , begin l ight jogging At 5 months Progress running and ear ly act iv i ty .Begin f igure 8, d i rect ion changes, s lopes. "MEDICINE CENTRE .Begin sport speci f ic exercises and indiv idual ski l ls . .Protect A C L for act iv i ty wi th a knee sleeve or taping. At 6 months I f a l l parameters are OK ar id you are Reconstruct ion conf ident of you abi l i ty , return gradual ly to fu l l act iv i ty. Using Level Five REMEMBER: IF IT HURTS OR SWELLS THEN YOU ARE DOING TOO MUCH. SLOW DOWN Holy Spirit Hospital 259 Wickham Terrace BRISBANE 4000 Ph. 07138322181 Fax: (07) 3834 6637 Dr Myers " I advise you of any var iat ions needed.
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Appendix F Window Funct ions for weight ing EMG data in the t ime domain pr ior to apply ing a Four ier t ransform
Comparisons were made between median frequencies estimated from three consecutive sections of the same EMG signal using different window functions. The four different window functions made no signif icant difference to the estimated median frequency and the differences were similar in magnitude to the measurement resolution (0.5 Hz) see tables below.
_ _ _ _ _ _ _ _ _ _ Hamming - - - - - - - - - Hann ing . . . . . . . . . . Dan ie l l
Summary Statistics I
Resolution 0.5 Hz mean SD % diff equiv Hz
Hamming 72.8 3.7 0.56 0.41 Hanning 72.8 3.7 0.56 0.41
Rectangular 72.4 3.9 0.11 0.08 Daniell 71.6 4.1 -1.01 -0.73
mean 72.3 3.9
SD 0 .5 0.2 n 3
Summary Statistics II ANOVA: Single Factor by WINDOW
SUMMARY
Groups Count Sum Average Variance Hamming 3 218.26 72.75 13.59 Hanning 3 218.26 72.75 13.59
Rectangular 3 217.29 72.42 15.58 Daniel l
3
214.84
71.61
16.53
ANOVA
Source of Var iat ion SS df MS F P-value
Between Groups 4.093 5 0.82 0.0544 0.99 Within Groups 182.00 12 15.17
Total
186.09
17
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Appendix G
Publications and presented papers
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Publications
International Journals L i , Raymond Che Tin, Chin, Ming Kai , Chan, Kai Ming, & Leung, John. (1988). Isokinet ic Muscular Test ing of the Hong Kong Nat ional Soccer Team---A Physiological Prof i le, Olympic Scient i f ic Congress Proceedings (pp. 212-217): Internat ional Olympic Commit tee. L i , Raymond Che Tin, Choi , Man Sierra, Chan, Kai Ming, Wu, Yi , & Chin, Ming Kai . (1995). Concentr ic Agonist and Eccentr ic Antagonist Peak Torque Rat ios of the Knee Measured Isokinet ical ly . The Hong Kong Journal of Sports Medicine and Sports Science, 1 , 66-70. L i , Raymond Che Tin, Wu, Yi , Maffu l l i , Nocola, Chan, Kai Ming, & Chan, Jul ie L C. (1996c). Eccentr ic and Concentr ic Isokinet ic Knee Flexion and Extension: A Rel iabi l i ty Study Using the Cybex 6000 Dynamometer. Br J Sports Med, 30 (2) , 156-160. L i , Raymond Che Tin, Mafful l i , Nicola, Chan, Kai Ming, & Hsu, Stephen Y C. (1996a). Isokinet ic Strength of the Quadriceps and Hamstr ings and Funct ional Abi l i ty of Anter ior Cruciate Def ic ient Knees in Recreat ional Athletes. Br J Sports Med, 30 (2), 161-164. Wu, Yi , L i , Raymond Che Tin, Mafful l i , Nicola, Chan, Kai Ming, & Chan Jul ie, L. C. (1997). Relat ionship Between Isokinet ic Concentr ic and Eccentr ic Contract ion Modes in the Knee Flexor and Extensor Muscle Groups. J Orthop Sports Phys Ther, 26(3) , 143-149.
Books Chan, Kai Ming, Mafful l i , Nocola, Korkia, Pirkko, & Li , Raymond Che Tin. (1996). Principles and Pract ice of Isokinet ic in Sports Medicine and Rehabi l i tat ion . Hong Kong: Wi l l iams & Wilk ins Asia-Paci f ic Ltd. L i , Raymond Che Tin, & Chan, Kai Ming. (1990). Rehabi l i tat ion of Anter ior Cruciate Ligament in Sports, Sports, Medicine, and Heal th (pp. 361-365): Elsevier Science Publ ishers B.V. Paper Presented at International Conferences L i , Raymond Che Tin. (1988). Isokinet ic Muscular Test ing of the Hong Kong Nat ional Soccer team--A Physio logical and Cl in ical Prof i le. Paper presented at the Seoul Olympic Scient i f ic Congress, Seoul, Korea 1988.
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Li , Raymond Che Tin. (1996). Rehabi l i tat ion of Anter ior Cruciate Ligament. Paper presented at the Br i t ish Orthopaedics Conference. L i , Raymond Che Tin, Y, Cheng Jack C, Guo, Xai , Chan, Kai Ming, & Parker, Anthony W. (1998). Range of Movement and Muscular Strength Character ist ics of Adolescents wi th Id iopathic Scol iosis , Austral ian Conference of Science and Medicine in Sport , Adelaide Oct 1998. L i , R.C.T. ; Parker, A.W.; Smeathers, J . . (2002) The Rel iabi l i ty and Bi lateral Discrepancy of Median Frequency for the Quadriceps and Hamstr ings as measured Isometr ical ly . Austra l ian Conference of Science and Medicine in Sport . Melbourne, 12-16 Oct 2002.
