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Effects of Soft Tissue Mobilization Techniques on Neuromotor Control and Stiffness in Hamstring Shortness Dohyeon Kim The Graduate School Yonsei University Department of Physical Therapy

Effects of Soft Tissue Mobilization Techniques on ... · Effects of Soft Tissue Mobilization Techniques on Neuromotor Control and Stiffness in Hamstring Shortness Dohyeon Kim Dept

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Page 1: Effects of Soft Tissue Mobilization Techniques on ... · Effects of Soft Tissue Mobilization Techniques on Neuromotor Control and Stiffness in Hamstring Shortness Dohyeon Kim Dept

Effects of Soft Tissue Mobilization

Techniques on Neuromotor Control and

Stiffness in Hamstring Shortness

Dohyeon Kim

The Graduate School

Yonsei University

Department of Physical Therapy

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Effects of Soft Tissue Mobilization

Techniques on Neuromotor Control and

Stiffness in Hamstring Shortness

Dohyeon Kim

The Graduate School

Yonsei University

Department of Physical Therapy

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Effects of Soft Tissue Mobilization

Techniques on Neuromotor Control and

Stiffness in Hamstring Shortness

A Masters Thesis

Submitted to the Department of Physical Therapy

and the Graduate School of Yonsei University

in partial fulfillment of the requirements

for the degree of Master of Science

Dohyeon Kim

December 2013

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This certifies that the masters thesis of Dohyeon Kim is approved.

Thesis Supervisor: Sunghyun You

Chunghwi Yi: Thesis Committee Member #1

Wanhee Lee: Thesis Committee Member #2

The Graduate School

Yonsei University

December 2013

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Acknowledgements

First of all, I would like to thank to God for my fruit. He leads me to the good way

as he planned at all times.

There are many valuable people who have devoted their efforts, time, and love for

this thesis. I would like to express gratitude advising Professor Sunghyun You. He

gave me the great research opportunity for master’s course. His continuous advice

and teaching was a great to expand my academic knowledge, social relationship, and

religious faith. I also sincerely thank to my committee members: Professor Chungwhi

Yi, his warm advice and invaluable feedbacks have encouraged during my master’s

course. I appreciate Professor Wanhee Lee for his good guidance. I warmly thank

Professor Ohyun Kwon, Sanghyun Cho, Hyeseon Jeon, and Heonseock Cynn who

have broadened my horizon and knowledge. I have also expressed appreciation to

Professor Jongman Kim who has guided and supported for a long time as my mentor.

I express sincerely thank members of Movement Healing Laboratory: Dongryul

Lee, Namgi Lee, Dongkoog Noh, Jaejin Lee, Jiwon Yoo, Jeongjae Lee for their

kindness, friendship, support, and intellectual exchange. Specially, my senior,

Dongryul Lee, he delicately took care of me like a brother. I never got his warm-

heartedness.

In particular, I wish to express my appreciation to Boram Choi, Sungdae Choung.

When I had difficulty, they always encouraged and coached how to solve the

problems. They were my emotional anchor. Additionally, I appreciate Sunyoung

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Kang, Joohee Park, Onebin Lim, Incheol Jeon, and Silah Choi. They are nice

colleagues and I will have good memories for them. I would like to thank to all of

members in the Graduate School Department of Physical Therapy. They are always

on my mind.

Finally, I wish to express my deepest gratitude to my father and mother for their

endless love, dedication, and favor. They also trust and pray for me all the time.

“Stagnant water is bound to corrupt.” I will constantly try to develop my personality

and intellect. I believe that this thesis is the first stepping-stone towards better

researcher. Thank you.

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Table of Contents

List of Figures ····································································· iii

List of Tables ······································································ iv

Abstract ············································································· v

Introduction ········································································· 1

Method ·············································································· 6

1. Subjects ······································································ 6

2. Instrumentation ····························································· 8

2.1. Surface Electromyography ·········································· 8

2.2. Isokinetic Torque and Stiffness Assessment ······················ 9

3. Experimental Procedures ················································· 13

3.1 Instrument-Assisted Soft Tissue Mobilization ···················· 13

3.2 Hold Relax ····························································· 15

3.3 Strain-Counterstain ··················································· 16

4. Statistical Analysis ························································ 17

Results ·············································································· 18

1. General Characteristics ··················································· 18

2. Knee Joint Muscle EMG Activity Ratio ······························· 20

3. Knee Joint Muscle Peak Torque Ratio ································· 22

4. Knee Joint Passive Stiffness ············································· 24

5. Knee Joint Range of Motion ············································· 26

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6. Measure of Correlation ··················································· 28

Discussion ········································································· 29

Conclusion ········································································· 33

References ········································································· 34

Abstract in Korean ································································ 43

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List of Figures

Figure 1. Active knee extension test ············································· 7

Figure 2. Biodex system isokinetic dynamometer ···························· 12

Figure 3. Instrument-assisted soft tissue mobilization ························ 14

Figure 4. The quadriceps and hamstring EMG activity ratio during knee

extension ································································ 21

Figure 5. The quadriceps and hamstring peak torque ratio during knee extension

············································································· 23

Figure 6. The passive stiffness during knee extension ························ 25

Figure 7. The knee joint ROM during active knee extension test ··········· 27

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List of Tables

Table 1. General characteristics of the subjects ······························ 19

Table 2. Q:H EMG activity ratio ··············································· 21

Table 3. Q:H peak torque ratio ·················································· 23

Table 4. Knee joint passive stiffness ··········································· 25

Table 5. Knee joint ROM during active knee extension test ················ 27

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ABSTRACT

Effects of Soft Tissue Mobilization Techniques on

Neuromotor Control and Stiffness in Hamstring Shortness

Dohyeon Kim

Dept. of Physical Therapy

The Graduate School

Yonsei University

The purpose of this study was to compare the effects of soft tissue mobilization

(STM) techniques on improving quadriceps and hamstring muscle electromyographic

(EMG) activity ratio, torque ratio, active knee extension range of motion (ROM), and

knee joint passive stiffness. Forty-five subjects (21 males and 24 females) with

hamstring tightness participated in this study. The subjects were assigned randomly to

each of the three soft tissue mobilization technique groups [instrument-assisted soft

tissue mobilization (IASTM), hold-relax (HR), and strain-counterstrain (SCS)].

Subjects with hamstring tightness have limited active knee extension test (more than

20°). Surface EMG was utilized to collect the quadriceps and hamstring muscle

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activity and Biodex System Isokinetic Dynamometer was used to measure muscle

torque and knee joint passive stiffness during knee extension and flexion. One-way

analyses of variance were used to determine the statistical significance of the

quadriceps and hamstring EMG activity and torque ratios, knee joint passive stiffness,

and active knee extension ROM in each technique. The significance level was set at

α=0.05. The quadriceps and hamstring EMG activity and torque ratios were

significantly increased in IASTM compared to HR, and SCS. Whereas knee joint

passive stiffness was significantly reduced in IASTM compared to HR and SCS.

Therefore, the results of this study suggest that IASTM technique may have improved

knee joint neuromuscular imbalance and knee joint passive stiffness by restoring

proper reciprocal inhibition between the quadriceps and hamstring in subjects with

hamstring tightness.

Key words: Hamstring tightness, Neuromuscular imbalance, Passive stiffness,

Reciprocal inhibition, Soft tissue mobilization.

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Introduction

Hamstring (HAM) muscle strain is common muscular system impairment among

sports injuries, which is often associated with neuromuscular imbalance in quadriceps

and hamstring muscles (Askling et al. 2000). This muscle strain occurs during the

end-range hip flexion coupled with knee extension movement (Heiderscheit et al.

2010). There are several factors influencing hamstring strain, which may include

neuromuscular imbalance (Orchard et al. 1997; Wilson, Wood, and Elliott 1991),

mobility or flexibility (Worrell et al. 1991), lumbopelvic core stability, and muscle

fatigue (Mair et al. 1996). Among them, neuromuscular imbalance between the

quadriceps and hamstring has been recognized as an important pathomarker for

muscle strain injury.

Janda has first coined the theoretical concept of neuromuscular imbalance, which

was defined as an impaired relationship between tonic-flexor system and phasic-

extensor system is based on the phylogenetic developmental kinesiology (Jull, and

Janda 1987). The tonic-flexor system is phylogenetically organized dominant, strong,

short, and facilitative (hamstring muscle) whereas the phasic-extensor system is less

dominant, weak, long, and inhibitive (quadriceps muscle) (Page, Frank, and Lardner

2010). This neuromuscular imbalance results in dys-synkinesis (incoordinated

coactivation around the joint) and overtime causes arthrokinematic decentration

(deviated pathway of the instantaneous center of joint rotation) and associated

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instability during movement. On the other hand, arthrokinematic decentration affects

neuromuscular synkinesis in terms of muscle activation time, amplitude, and the

orientation of muscle force vector and eventually influences the sensorimotor

program in central nervous system. If this neuromuscular imbalance or joint

centration is not mitigated, movement impairment occur along with joint degeneration

and pain (Coombs, and Garbutt 2002; Damiano, Kelly, and Vaughn 1995).

Neurophysiologically, muscle imbalance concept was based on Sherrington’s

reciprocal inhibition of agonist quadriceps due to overactivation the antagonist

hamstring muscle (Sherrington 1907). This reciprocal inhibition leads to muscular

tightness or reduction in sarcomere number (Hayat et al. 1978). Hartig, and

Henderson (1999) suggested that prolonged hypertonic activation of hamstring

reciprocally inhibited quadriceps which results in overuse stress fractures,

patellofemoral pain syndrome (PFPS), and hamstring muscle strains.

Neuromuscular imbalance is mainly characterized by altered muscle length-tension

relationship, and muscle recruitment patterns (Janda 1993). For example, hamstring

overactive-induced tightness changes sarcomere and viscoelastic properties and

reciprocally inhibits sufficient quadriceps activation (compromised knee extension

force), thereby limiting kinematic terminal knee extension during sports activity.

Decreased neuromuscular balance or synkinesis was responsible for overuse

hamstring injury (Devan et al. 2004). In a previous study, Rosene, Fogarty, and

Mahaffey (2001) revealed that normal peak torque ratio between quadriceps and

hamstring (Q:H) ratio was 2.0 during concentric knee extension and flexion

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movements in healthy collegiate athletes. In a prospective study, the adequate

neuromuscular balance between quadriceps and hamstring muscles was crucial to

prevent hamstring injury in soccer players (Croisier et al. 2008). EMG amplitude

study showed that normal muscle balance ratio between quadriceps and hamstring

muscles was 3.0 (low resistance, body weight 0%), 2.76 (medium resistance, body

weight 4%), and 2.32 (high resistance, body weight 8%), respectively in healthy

subjects during single-limb squat (Shields et al. 2005). However, Solomonow et al.

(1987) observed that direct stress on the anterior cruciate ligament increased the

hamstring activation, but reciprocally decreased the quadriceps activation during an

open kinematic kicking as commonly seen in soccer kicking or marathon running.

EMG onset time studies demonstrated that vastus medialis oblique (VMO) first

activated, followed by either vastus lateralis (VL) or hamstring in healthy control

whereas VL first activated, followed by either VMO or hamstring in subjects with

PFPS during knee extension (Cowan et al. 2002). In addition, Sole et al. (2012) found

that earlier onsets of the hamstring muscles are likely to occur during a movement

from double- to single limb stance in participants with a history of hamstring injury.

This prolonged overactive hamstring muscle results in soft tissue shortness and

reciprocally inhibited quadriceps muscle during open kinematic chain exercise. To

optimize balanced neuromuscular performance overactive hamstring muscle and

associated shortness should be treated to reduce the risk of hamstring injury as

effective intervention strategies.

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Conventionally, manual therapeutic approaches such as hold-relax (HR), strain-

counterstrain (SCS), and soft tissue mobilization (STM) have been commonly used to

improve hamstring hypertonicity and associated flexibility (Feland, Myrer, and

Merrill 2001; Hopper et al. 2005; Lewis, and Flynn 2001), but outcome results were

variable. Moreover, the manual mobilization techniques are often physically

demanding and overtime a combination of overuse and improper biomechanics can

cause DeQuervain’s tenosynovitis or other musculoskeletal impairments among the

therapists (Cromie, Robertson, and Best 2000).

Feland, Myrer, and Merrill (2001) suggested that both static stretching group and

contract-relax proprioceptive neuromuscular facilitation (PNF) stretching group

increased in post test result than pre test in athletic population with hamstring

tightness and median difference was significantly greater in PNF stretching group.

Lewis, and Flynn (2001) revealed that pain and disability reduced following SCS

treatments in two weeks in patients with low back pain. Moreover, McGill Pain

Questionnaire and the Oswestry Low Back Pain Disability Questionnaire score was

significantlly reduced (Lewis, and Flynn 2001). Furthermore, Collins (2007) reported

reduction of 2 points in overallpain as measured with a numeric pain rating scale after

2 months. In addition, increase in function was noted such as gait ability (cadence)

and single limb stance (time). Nevertheless, these may be labor demanding and time

consuming approach and also therapist’s manual assistance or resistance.

To enhance such musculoskeletal impairment condition, instrument-assisted soft

tissue mobilization (IASTM) technique has recently gained a widespread application

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among many manual therapists to improve soft tissue extensibility because it has

superior advantages and promising evidence to specifically target the hypertonic

muscle and related muscle fiber shortness with specialized instruments (Fowler,

Wilson, and Sevier 2000; Sevier et al. 2000). Howitt, Wong, and Zabukovec (2006)

suggested that flexion or extension of thumb ROM was restored full range after

application of Graston instrument-assisted soft tissue mobilization during 4-week

period. Similarly, Davey et al. (2004) reported that 27° of active dorsiflexion was

recovered in subjects with myofascial pain and range of motion (ROM) deficit

because of improved functional biomechanics and soft tissue structures. In

microscopic study, Loghmani, and Warden (2009) suggested that medial collateral

ligament (MCL) were stiffer (39.7%), and stronger (43.1%) after 3 sessions per week

for 4 weeks treatment.

However, the therapeutic mechanisms underpinning these techniques are unknown.

Therefore, the purpose of this study was to compare the effects of STM techniques

(HR, SCS, and IASTM) on neuromuscular imbalance [EMG activity ratio, peak

torque ratio, passive stiffness, and ROM during active knee extension test (AKET)] in

individuals with hamstring shortness. We hypothesized that there will be difference in

Q:H EMG activity ratio, Q:H peak torque ratio, knee joint passive stiffness, and ROM

during AKET among the three manual techniques: HR, SCS, and IASTM.

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Methods

1. Subjects

For this study, a convenience sample of forty-five adults with hamstring tightness

volunteered for this study. HR group 15 (7 males and 8 females; mean age ± standard

deviation = 23.1 ± 2.5 years), SCS group 15 (7 males and 8 females; mean age ±

standard deviation = 21.3 ± 1.6 years), and IASTM group 15 (7 males and 8 females;

mean age ± standard deviation = 21.5 ± 2.5 years) was recruited from local

community in Wonju City, Republic of Korea. This experimental protocol was

approved by Yonsei University Wonju Campus Human Studies Committee (2013-13).

Informed consent was obtained from all participants prior to the study. Inclusion

criteria for adults with hamstring tightness included (1) free from any current medical

conditions, (2) more than 20 years of age, (3) limited active knee extension ROM

(more than 20°) (Magee 2007; Spernoga et al. 2001). Exclusion criteria included (1)

neuromotor or musculoskeletal impairments or previous surgical history in knee joint,

(2) pregnant female, (3) hypertension, (4) Body mass index (BMI) is greater than or

equal to 25 kg/m2.

The demographic and anthropometric data of the subjects are presented in Table 1.

Prior to data acquisition, all participants also completed a demographic and health

questionnaire, and routine clinical tests including cutaneous (touch and pressure) and

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kinesthetic senses (position sense), and ROM of the knee during AKET. Especially,

AKET was used to measure length of hamstring muscle: For AKET assessment, test

leg was fixed in 90° hip and knee flexion with ankle neutral position while the other

leg was maintained with neutral position in supine. A cloth strap was placed over the

thigh and another cloth strap across the both anterior superior iliac spine. A pipe

frame cross-bar was used to ensure 90° hip flexion. The subjects were then asked

extend the knee until examiner felt myoclonus in the subject’s hamstring muscle.

When examiner felt myoclonus on the knee, subjects were required to stop extending.

The knee angle was measured between two arms of universal goniometer. A stable

arm was positioned lateral epicondyle of the femur and moving arm is over the line

that was drawn from fibular head to the lateral malleolus (Norkin, and White 2003).

Figure 1. Active knee extension test.

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2. Instrumentation

2.1 Surface Electromyography

Neuromotor control is defined as sensorimotor processes that are involved in

controlling Q:H EMG activity and imbalance ratio. Surface EMG data were collected

using a Noraxon TeleMyo 2400T system (Noraxon Inc., Scottsdale, AZ, USA).

Before the electrode attachment, skin preparation was performed on the body site

involving shaving, cleaning with alcohol prep pad, and sanding. A bipolar Ag/AgCl

surface electrode (Blue Sensor, Olyystyke, Denmark) with a diameter of 1.8 cm and

an interelectrode distance of 2 cm were placed on the five muscles on the dominant

leg: Rectus femoris (RF), VMO, VL, and lateral and medial HAM. The electrode for

RF was attached approximately half the distance between the knee and the iliac spine.

The VMO electrode was placed on the center of muscle belly, approximately 2 cm

medial and oblique side above the superior rim of patella and was placed at a 55°

oblique angle. The VL electrode was positioned at 3 cm lateral and oblique side

above the patella. The lateral HAM active electrode was attached parallel to the

muscle fiber on the lateral aspect of the thigh. For medial HAM, active electrode was

placed on the medial aspect of the center of back of thigh, 3 to 4 cm apart between

medial and lateral side (Criswell 2010). The EMG signals were collected at sampling

rate of 1500 Hz, band-pass filtered between 20 and 450 Hz, and notch filtered at 60

Hz. The digital signals were full-wave rectified and the EMG activity was calculated

by root mean square (RMS) moving window of 100 ms epoch. The EMG activity was

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normalized as maximal voluntary isometric contraction (MVIC) for each muscle. For

MVIC of the RF, VMO, and VL muscles, participants were seated on a backless chair

with 90° hip flexion and 60° knee flexion. For MVIC of the HAM muscles,

participants positioned prone with the hip and knee in 0° and 30° flexion respectively.

Then they conducted 5 seconds isometric knee extensions and flexion against the

manual resistance. The EMG signals collected during knee extension and flexion

were represented as a RMS processed percentage of MVIC (%MVIC). EMG data

were used to analyze quadriceps and hamstring muscle activity using MyoResearch

1.08 XP software (Noraxon, Inc., Scottsdale, AZ, USA). The collected signal within

the first and last one second of each isokinetic contraction was not used for analysis.

Therefore, the signal was analyzed in the middle 3 seconds.

2.2 Isokinetic Torque and Passive Stiffness Assessment

Isokinetic torque and passive stiffness were assessed on the calibrated Biodex

System Isokinetic Dynamometer (Biodex Medical, Shirley, NY, USA). For isokinetic

torque, repetitive and reciprocal concentric isokinetic knee extension and flexion was

measured in the concentric and concentric (CON/CON) mode at an angular velocity

of 60°/sec. For stiffness, passive knee extension and flexion were performed in the

passive mode at an angular velocity of 5°/sec. Before the testing procedure, all

participants were familiarized with the experimental procedure by practicing at

submaximal level and then performed 5 maximal-effort concentric contractions with

their dominant leg. Dominant leg was determined by requesting the participants

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which leg they would familiar kicks a ball. Subjects sat on the Biodex Dynamometer

chair and were fixed using torso, pelvic, and thigh velcro straps to allow minimized

body movements. Axis of the dynamometer was aligned with the both knee axis and

the cushion setting for reducing the effect of movement deceleration at end-range.

Gravity correction was gained by determining the torque on the dynamometer

resistance attachment with relaxed and knee full extension. During the tests, loud

verbal comment was used by the estimator so that experimental subjects were

encouraged to kick out and pull back. Each subject was instructed to fold both arms

across their chest and provided visual feedback from the Biodex computer monitor to

assist maximal-effort contractions (Kim, and Kramer 1997; Pincivero, Gandaio, and

Ito 2003).

In order to estimate knee joint passive stiffness, The Biodex dynamometer was set

up in the passive mode for extension and flexion. Five cyclic passive repetitions were

performed automatically to full ROM at angular velocity of 5°/sec. Surface EMG was

used to ensure muscle contraction during passive extension and flexion.

Stiffness is well-defined as the resistance of body to deformation by an applied

force along a given degree of freedom. In our study, the slope of these force-angle

displacement ratios represents knee joint stiffness during knee passive extension

(Granata, Padua, and Wilson 2002). Stiffness was computed with the following

equation (Granata, Padua, and Wilson 2002; Padua et al. 2006):

Kknee= ∆T / ∆θ

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where ∆T represents the known perturbation torque, ∆θ (degrees) is the impact-

dependent angular displacement. The T (muscle torque) equation is then expressed as:

T = Q · r

where Q represent the value of the weight hung on the lever, and r is the lever arm of

force Q, measured as the distance between its point of application and the rotation

axis of the lever.

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Figure 2. Biodex system isokinetic dynamometer.

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3. Experimental Procedures

All tests were standardized and consistently performed according the experimental

checklist. All subjects performed a pre-test with maximum effort and then

participants are treated with manual physical therapy intervention including HR, SCS,

and IASTM. Lastly, all subjects performed a post-test.

3.1 Instrument-Assisted Soft Tissue Mobilization (IASTM)

Participants received IASTM with Dr. YOU STM instrument (Y1) by using stroke

both cranial and caudal direction. The participants were positioned in prone position

with knee flexion between 30° and 60°. Then a therapist who has been certified Dr.

YOU STM courses performed stroking to the hamstrings of participants with soft

tissue mobilization cream. The force was provided when participants felt a pain (VAS

level 3) and avoids too much pressure for effective treatment. The participants were

applied to the stroke of the tool on his or her hamstring muscle for 2 minutes

(Hammer, and Pfefer 2005).

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Figure3. Instrument-assisted soft tissue mobilization (A. Dr. YOU STM, B. IASTM technique).

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3.2 Hold Relax (HR)

The HR stretching was performed with no hip and trunk rotation. Programmed time

for contracting, relaxing, and stretching were used to regulate or standardize methods.

First, the investigator passively stretched the subject’s hamstring muscle until the

subject told a stretch feeling and held this position for 7 seconds. Second, the subject

contracted the hamstring muscle maximally and isometrically for 7 seconds by trying

to push his or her leg backwardly toward the resistance of the investigator’s shoulder.

After the hamstring contraction, the subject calmed down for 5 seconds for non-

fatigue. Finally, the investigator stretched the subject’s hamstring muscle for 7

seconds until a mild stretch feeling was told. All stretching procedure was completed

on the dominant lower extremity (Spernoga et al. 2001).

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3.3 Strain-Counterstrain (SCS)

SCS is a passive mobilization technique in which the subject’s body (shank) is

positioned into the greatest comfort position for muscle relaxation. For treatment,

subjects were naturally positioned prone for the SCS intervention. And then the

investigator found the subject’s tender point during knee extension by palpation.

After detection of tender point, the therapist applied a mild pressure until subjects felt

pain from pressure sensation. Subject’s lower limb was passively flexed to reduce the

pain under the palpating finger. This specific position is kept throughout the 90

seconds treatment period. Finally, their lower limb was then passively moved to

neutral position. It has been recommended that keeping contact with the tender point

during the treatment period for a therapeutic effect (Chaitow 1998; 2002).

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4. Statistical Analysis

All statistical analyses were performed using PASW Statistics 20 (Norusis/SPSS

Inc., Chicago, IL, USA). One-way analysis of variance (ANOVA) was used to

estimate difference of general characteristics between groups, Q:H EMG activity ratio,

Q:H torque ratio, knee joint passive stiffness, and ROM during AKET including HR,

SCS, and IASTM. If a significant difference between conditions was observed, the

Bonferroni comparison was used as a post hoc test. The results are expressed as mean

standard deviation (SD), and all statistical significance level was set at α=0.05.

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Results

1. General Characteristics

The general clinical characteristics of the subjects are shown in Table 1. There was

no significant difference in age, height, weight, BMI, and hamstring length among

three groups.

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Table 1. General characteristics of the subjects (N=45)

Parameter HR a SCS b IASTM c

Age (yr) 23.1 ± 2.5 e 21.3 ± 1.6 21.5 ± 2.4

Height (cm) 167.5 ± 8.3 167.8 ± 8.8 167.5 ± 7.5

Weight (kg) 58.7 ± 11.1 58.4 ± 8.7 59.1 ± 11.6

BMId (kg/m2) 20.7 ± 2.1 20.7 ± 2.0 20.9 ± 2.7

Muscle length (°) 140.0 ± 12.0 143.7 ± 9.0 146.7 ± 11.9 aHR: Hold-relax. bSCS: Strain-counterstain. cIASTM: Instrument-assisted soft tissue mobilization. dBMI: Body mass index. dMean ± standard deviation.

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2. Knee Joint Muscle EMG Activity Ratio

The Q:H EMG activity ratio of subjects in three groups was shown in Table 2 and

Figure 4. The Q:H EMG activity ratio was significantly changed in IASTM compared

to HR and SCS (p < 0.05).

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Table 2. Q:H EMG activity ratio

HR a SCS b IASTM c F p

Pre-test 3.11 ± 1.53d 3.12 ± 1.72 3.09 ± 1.29 0.012 0.988

Post-test 3.20 ± 1.71 3.17 ± 1.74 4.7 ± 1.59* 5.481 0.008*

aHR: Hold-relax. bSCS: Strain-counterstain. cIASTM: Instrument-assisted soft tissue mobilization. dMean ± standard deviation.

Figure 4. The quadriceps and hamstring EMG activity ratio during knee extension. *p < 0.05.

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3. Knee Joint Muscle Peak Torque Ratio

The Q:H peak torque ratio of subjects in three groups was shown in Table 3 and

Figure 5. The Q:H peak torque ratio was significantly changed in IASTM compared

to HR and SCS (p < 0.05).

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Table 3. Q:H peak torque ratio

HR a SCS b IASTM c F p

Pre-test 1.77 ± 0.45d 1.78 ± 0.50 1.75 ± 0.45 0.013 0.987

Post-test 2.18 ± 0.44 2.16 ± 0.48 2.34 ± 0.47* 6.267 0.004*

aHR: Hold-relax. bSCS: Strain-counterstain. cIASTM: Instrument-assisted soft tissue mobilization. dMean ± standard deviation.

Figure 5.The quadriceps and hamstring peak torque ratio during knee extension. *p < 0.05.

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4. Knee Joint Passive Stiffness

Knee joint passive stiffness data collected in the sagittal (extension and flexion)

plane presented in Table 4 and Figure 6. Knee joint passive stiffness was

significantly changed in IASTM compared to HR and SCS (p < 0.05).

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Table 4. Knee joint passive stiffness

HR a SCS b IASTM c F p

Pre-test 0.2701 ± 0.06 d 0.2707 ± 0.07 0.2696 ± 0.07 0.001 0.891

Post-test 0.2368 ± 0.06 0.2420 ± 0.07 0.2108 ± 0.06* 9.571 p < 0.001*

aHR: Hold-relax. bSCS: Strain-counterstain. cIASTM: Instrument-assisted soft tissue mobilization. dMean ± standard deviation.

Figure 6. The passive stiffness during knee extension. *p < 0.05.

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5. Knee Joint Range of Motion

AKET data of subjects in three groups was shown in Table 5 and Figure 7. There

was no significant difference in AKET in IASTM compared to HR and SCS (p >

0.05).

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Table 5. Knee joint ROM during active knee extension test

HR a SCS b IASTM c F p

Pre-test 140 ± 11.97 d 143.67 ± 9.03 146.61 ± 11.93 1.366 0.267

Post-test 150.33 ± 8.84 150.33 ± 9.03 160 ± 11.55* 3.001 0.061

aHR: Hold-relax. bSCS: Strain-counterstain. cIASTM: Instrument-assisted soft tissue mobilization. dMean ± standard deviation.

Figure 7.The knee joint ROM during active knee extension test.

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6. Measure of Correlation

Negative correlations were found between knee joint passive stiffness and knee

extension ROM (r = -0.73, p < 0.05) and between hamstring EMG activity and knee

extensor torque (r = -0.75, p < 0.05).

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Discussion

The present study compared the immediate therapeutic effects on neuromuscular

imbalance and associated motor control mechanism of IASTM, HR, and SCS. As

anticipated, IASTM technique more increased in Q:H EMG activity and torque ratios,

active knee terminal extension ROM and decreased knee joint passive stiffness than

HR and SCS. To the best of our knowledge, this is the first clinical trial highlighting

the superior effects of IASTM on restoring neuromuscular imbalance in individuals

with hamstring tightness.

Neuromuscular imbalance as defined Q:H EMG amplitude ratio demonstrated

greatest improvement in IASTM (1.61) than HR (0.09), and SCS (0.04) conditions.

This finding was consistent with Aagaard et al. (1998) who reported 1.85-5.66 during

open isokinetic knee extension (30°/sec) in healthy young adults without hamstring

shortness. Shields et al (2005) showed 2.32-3.0 in normal healthy adults during close

kinetic single limb squat. The current finding suggests that IASTM technique was

most effective to restore muscle imbalance by reciprocally inhibiting inherently

overactive and short hamstring and facilitating the less active quadriceps (Page, Frank,

and Lardner 2010; Sherrington 1907). Additionally, in the present study, the HR

technique decreased hamstring activity. Osternig et al. (1986) demonstrated a more

significant reduction in hamstring EMG activity during the 80 seconds passive static

stretch technique than agonist contract-relax in younger adults, indicating effective

inhibition effect of the overactive and short hamstring.

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Isokinetic strength imbalance was evaluated by computing the Q:H peak torque

ratio. IASTM revealed a more increase in the Q:H ratio (0.58) than HR (0.41) and

SCS (0.37). This result was in line with previous data which showed increased Q:H

peak knee extension torque ratio (0.24) after static hamstring stretching in healthy

women (Costa et al. 2013). The static hamstring stretching resulted in stretching-

induced force inhibition of the hamstring muscle in healthy men but quadriceps

torque was not measured (Herda et al. 2008).

Passive stiffness demonstrated greatest improvement in IASTM (22%) than HR

(12%), and SCS (10%) conditions. Recent studies (Marshall, Cashman, and Cheema

2011; Nordez, Cornu, and McNair 2006; Witvrouw et al. 2004) showed decreased

passive knee extension stiffness following hamstring stretching. Specifically, passive

stiffness was decreased (27.6%) after five 30 seconds static stretching in healthy

participants (Nordez, Cornu, and McNair 2006). Marshall, Cashman, and Cheema

(2011) reported that passive stiffness was reduced by 31% after 4 weeks of passive

hamstring stretching exercise in healthy individuals.

Active knee extension ROM data showed a significant within-group main effect,

but IASTM (14°) tends to be more effective than other HR and SCS techniques (10°

and 7°) although statistical significance failed to reach its significance level (p < 0.06).

Wiemann and Hanhn (1997) demonstrated that knee ROM was increased both static

(7°) and dynamic (7°) after 15 min hamstring stretching in healthy male adults. Chan,

Hong, and Robinson (2001) showed that passive knee extension ROM was increased

11.2° after 8 weeks hamstring stretching training in healthy young adults. Reid, and

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McNair (2004) demonstrated that knee extension ROM was improved to 6.0 ± 6.8°

after once a day on the fifth consecutive days of the week for 6 weeks hamstring

stretching in healthy male subjects.

Moreover, correlational statistics showed a close inverse relationship between knee

joint passive stiffness and knee extension ROM (r = -0.73, p < 0.05), suggesting that

soft-tissue mobilization techniques were beneficial for hamstring viscoelasticity.

Kubo et al. (2001) reported that soft-tissue mobilization or stretching increased

viscoelasticity and associated tissue extensibility in animal or human. A significant

inverse correlation between hamstring EMG activity and knee extensor torque was

observed (r = -0.75, p < 0.05), indicating that hamstring inhibition resulted in

increased quadriceps activation, thereby improving overall knee extension strength.

Hamstring inhibition was obtained from STM or stretching, which helped enhancing

quadriceps activation.

Taken together, our novel results showed that IASTM was most effective to

enhance neuromuscular imbalance, passive stiffness, and ROM in hamstring

shortness when compared to the conventional STM techniques. Most importantly, the

present study has a clinical implication that IASTM technique may be effective

clinical technique for individual with muscle tightness and hypo-mobility. Eventually,

this innovative rehabilitation technique could be less labor intensive and cost effective

for IASTM trained clinicians.

Our study has two main limitations. First, this study established a short term

clinical effect of IASTM. Hence, further long-term follow-up study should be

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fulfilled to proof comprehensive IASTM effect. Second, future studies are needed to

identify the contraction type (i.e., eccentric contraction) to provide more meaningful

clinical implication because most hamstring injury occurs during eccentric

contraction or loading. Further investigations and clinical trials are necessary to

determine whether the improvements in muscle and torque ratio, and passive stiffness

can be maintained to recover neuromuscular imbalance in people with hamstring

shortness.

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Conclusion

As a first clinical trial in developing an effective neurorehabilitation technique,

our present study demonstrated the effectiveness of IASTM technique which is

made for restoring knee joint muscle imbalance associated with lack of reciprocal

inhibition during knee extension in subjects with hamstring tightness. Our results

provide promising evidence that IASTM improved neuromuscular imbalance and

peak terminal knee extension angle and moment, while decreasing hamstring

stiffness and overactivation. Clinically, this present finding suggests that IASTM

may be an effective alternative to enhance knee joint extension extensibility in

patients with hamstring shortness or tightness.

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국문 요약

연부조직 가동술이 넙다리뒤근 활성도 및 스티프니스에

미치는 영향

연세대학교 대학원

물리치료학과

김 도 현

본 연구의 목적은 넙다리뒤근 단축이 있는 대상자에게 세 가지 서로 다

른 연부조직 가동술(유지-이완, 긴장-반긴장, 도구-도움 연부조직 가동

술)을 적용하였을 때 근육의 유연성, 근활성도, 신경역학적 스티프니스의

변화를 비교함으로써 무릎관절 근육 불균형 개선에 효과적인 치료방법을

찾고자 하는 것이다. 45명의 넙다리뒤근 단축이 있는 대상자가 본 연구에

참여하였으며 각 치료 기술마다 15명씩 무작위 할당하여 배정하였다. 넙

다리뒤근 단축은 능동슬관절신전 검사를 하여 20도 이상인 성인을 대상으

로 하였다. 넙다리네갈래근과 넙다리뒤근 활성비를 비교하기 위해 표면 근

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전도를 사용하였으며 무릎관절 토크와 신경역학적 스티프니스를 비교하기

위해 등속성 장비를 사용하였다. 넙다리네갈래근과 넙다리뒤근 활성비, 토

크비, 신경역학적 스티프니스 개선 효과를 알아보기 위해 통계학적 검정으

로 일 방향 분산분석을 사용하였다. 통계검정을 위한 유의수준은 α=0.05

로 설정하였다. 넙다리네갈래근과 넙다리뒤근 활성비와 토크비가 유지-이

완군과 긴장-반긴장군과 비교했을 때 도구-도움 연부조직 가동술군에서

유의하게 증가하였다. 반면에 신경역학적 스티프니스는 유지-이완 군과

긴장-반긴장군과 비교했을 때 도구-도움 연부조직 가동술군에서 유의하

게 감소하였다. 따라서, 본 연구의 결과는 도구-도움 연부조직 가동술이

넙다리뒤근 단축이 있는 성인의 넙다리뒤근의 교대적 억제를 회복시키고

신경근육적 불균형을 개선시킨 것으로 생각한다.

핵심 되는 말: 교대적 억제, 넙다리뒤근 단축, 신경근육적 불균형,

신경역학적 스티프니스, 연부조직 가동술.