EFFECT OF MANIPULATED VISUAL FEEDBACK ON THE FORCE OUTPUT OF ISOKINETIC ELBOW FLEXION AND

EXTENSION PERFORMED BY UNIVERSITY MALE STUDENTS

BY

GE LI

07050593

AN HONOURS PROJECT SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF

BACHELOR OF ARTS

IN

PHYSICAL EDUCATION AND RECREATION MANAGEMENT (HONOURS)

HONG KONG BAPTIST UNIVERSITY

APRIL 2010

HONG KONG BAPTIST UNIVERSITY

23th APRIL, 2010

We hereby recommend that the Honours Project by Mr. Ge Li entitled “Effect of

Manipulated Visual Feedback on the Force Output of Isokinetic Elbow Flexion and

Extension Performed by University Male Students”

be accepted in partial fulfillment of the requirements for the Bachelor of Arts Honours

Degree in Physical Education And Recreation Management.

_______________________________ _______________________________

Prof. Chow Bik Chu Dr. Tong Kwok Keung

Chief Adviser Second Reader

DECLARATION

I hereby declare that this honours project “Effect of Manipulated Visual Feedback on

the Force Output of Isokinetic Elbow Flexion and Extension Performed by University

Male Students” represents my own work and had not been previously submitted to this or

other institution for a degree, diploma or other qualification. Citations from the other

authors were listed in the references.

________________________ Student Name

Date

ACKNOWLEDGEMENTS

I would like to express my deepest gratitude to my chief supervisor Prof. Chow Bik

Chu for her generous guidance and unfailing support throughout the whole project period.

I am truly grateful to her helpful suggestions and comments on the initial drafts.

In addition, sincere thanks go to Mr. Fung Ying Ki, the graduate stundent of Hong

Kong Baptist University, Department of Physical Education for his kindly instruction on

my project.

_____________________________

Student’s signature

Department of Physical Education

Hong Kong Baptist University

Date: ________________________

ABSTRACT

Manipulated visual feedback was not well studied about its efficacy on strength training.

A total of 30 university male students aged from 19 to 25 participated in the study and

assigned into one Control Group (CG), Experimental Group of Underrated Report (EGU)

and Experimental Group of Overrated Report (EGO). The subject performed eight

repetition-maximums (RMs) elbow flexion and extension on isokinetic dynamometer. The

video of real-time work value bar chart was captured in the first test and further edited

according to subject’s group. The video was played to subjects when performing eight

RMs elbow flexion and extension in the third test. Video played to CG was not

manipulated. The dynamic bar chart of video played to EGU was manipulated into

irrationally low and fading bar. That of EGO was into high and increasing one. The result

of Contrast test for ANOVA indicated no significant difference between the average peak

torque of CG and EG (p < 0.05). But the different manipulation aroused different

physiological response on the working muscles.

TABLE OF CONTENTS

CHAPTER Page

1. INTRODUCTION……………………………………………….…..……1 Statement of the Problem………………………………………....….2 Hypothesis ………………………………………………...…..….….2 Definition of Terms ………………………………………..….….….2 Delimitations……………………………………………….…...........4 Limitations………………………………………………..…….……5 Significance of the Study..………………………………..…….……6

2. REVIEW OF LITERATURE…………………………………..……….…7

Concurrent studies on the Effect of Visual Stimulation on Sport Performance…………………………………………..…….…7 Biofeedback Applications in Exercise Science and Physical Education ……………………………………………….…11 Application of Isokinetic Dynamometer in Exercise Science…….…13 Summary…………………………………………………….......…..15

3. METHOD………………………………………………………..….........17

Subjects……………………………………………….......................17 Testing Apparatus………………………………..………...…….….18 Pilot Testing……………………………………………….…..…….21 Procedures………………………………………………….…….....21 Method of Analysis…………………………………………………33

4. ANALYSIS OF DATA……………………………….…………….….....34

Results………………………………………………………….…...34

CHAPTER Page Discussions…………………………………………………..………..48

5. SUMMARY AND CONCLUSIONS……………………………..………..57

Summary of Results……………………………………………….….57 Conclusion………………………………………………………….…58 Recommendations of Further Study…………………………….…….58

REFERENCES………………………………………………………………..............60 APPENDIX…................................................................................................................65

A. Consent Form to Students (Chinese Version)………………………………65

B. Consent Form to Students (English Version)………………………… ……66

C. Physical Activity Readiness Questionnaire………………………………...68

D. Post-test Illustrations……………………………………………………….69

E. Two-Tailed Independent T-Test (Reference Only)…………………………70

LIST OF TABLES

TABLE Page

1. The Average Peak Torque of Eight-RM Elbow Flexion and

Extension during Pre-test by Descending Order in Reference

to Sum and the Result of Grouping…………………………………..……37

2. Descriptive Statistic for Pre-test Average Peak Torque ……………..…….39

3. The Average Peak Torque of Eight-RM Elbow Flexion and

Extension during Post-test by Descending Order in Reference

to Sum and the Result of Grouping………………………………..……….41

4. Descriptive Statistic for Post-test Average Peak Torque……………..…….43

5. Comparison between Pre-test Sum and Post-test Sum of

Average Peak Torques…………………………………………….…..……44

6. Result of One-Way ANOVA on the PreSUM, PostSUM,

and % Change among Three Groups (N=29)………………………………46

7. Result of the Contrast test for One-Way ANOVA (N=29)…….............…...47

LIST OF FIGURES

FIGURE Page

1. Sample of Work Report ……………………………………………………20

2. Sample Line-Chart………………………………………………………….20

3. Ergonomic Setting…………………………………………………………..23

4. CSMi Humac Norm Testing and Rehabilitation System……………………25

5. Flow Chart of Entire Experiment……………………………………..…….25

6. Edited Video for Experimental Group (Overrated Report)…………………28

7. Edited Video for Experimental Group (Underrated Report)………………..28

8. The Subject’s Posture during Post-test……………………………..………30

9. Sample Uutput Work Report Produced by Dynamometer………………….35

1

Chapter 1

INTRODUCTION

Do what people see during physical exercise influence the efficacy of training? Does

manipulated visual feedback affect the sport performance more significantly than without

manipulation? Although previous investigators have observed that knowledge of

performance via visual feedback tends to enhance performance during an isokinetic test

(Kim and Kramer, 1997), few researches related to the manipulated visual feedback in

exercise and training was conducted.

Among the limited studies in manipulated visual feedback, most researches were

related to motor learning. Manipulation was usually achieved by physical method e.g.

varying the illumination on both sides of a one way mirror. In this study, the visual

feedback was well manipulated by computer graphic editing.

On the other hand, the development of biofeedback technology also provided a lot of

evidences that visual feedbacks, as a broader concept, can enhance the force output

produced by muscle. Many visual biofeedback therapies also provided feasible ideas in

exercise science and physical education. Although not counted as biofeedback according to

the definition listed in later section, the experiment process in this study adopted the

common idea of biofeedback therapy, which is to interact with real-time feedback

information produced by instruments to achieve certain physiology alteration.

The purpose of this study was to assess the effect of manipulated visual feedback

2

aroused by real-time report on arm muscles’ force output in university male students by

using isokinetic dynamometer. The manipulated real-time report was dynamic bar-chart

work report in which the last four bars were edited into irrationally high (low) and kept

increasing (fading).

Statement of Problems

The effect of visual feedback on physical education or physical exercise was not

well studied. The visual feedback is not well adopted in athletes’ training currently.

Furthermore, few researches were conducted on the effect of manipulated real-time visual

feedback.

Hypothesis

The following hypothesis and questions were set in the study:

1. The average peak torque value of eight repetition-maximums elbow flexions and

extensions would not be enhanced by the visual feedback produced by underrated

and fading work report in the university male students.

2. The average peak torque value of eight repetition-maximums elbow flexions and

extensions would not be inhibited by the visual feedback produced by overrated

and increasing work report in the university male students.

Definition of Terms

The following terms were operationally defined especially for this study:

Visual Feedback

Visual feedback in this study described the situation when output report of the elbow

3

flexion and extension produced by the dynamometer influenced the same event (elbow

flexion and extension).

Biofeedback

Biofeedback is a process that enables an individual to learn how to change

physiological activity for the purposes of improving health and performance. Precise

instruments measure physiological activity such as brainwaves, heart function, breathing,

muscle activity, and skin temperature. These instruments rapidly and accurately "feed

back" information to the user. The presentation of this information — often in conjunction

with changes in thinking, emotions, and behavior — supports desired physiological

changes. Over time, these changes can endure without continued use of an instrument (The

Association for Applied Psychophysiology and Biofeedback [AAPB], 2008). The

experiment of this study is not counted as biofeedback according to the entire procedure

listed in Chapter 3.

Isokinetic

The action in which the rate of movement is constantly maintained through a

specific range of motion even though maximal force is exerted (Powers & Howley, 2007).

Powers and Howley added isokinetic means movement at a constant rate of speed. A

variable-resistance isokinetic dynamometer is an electronic-mechanical instrument that

maintains a constant speed of movement while varying the resistance during a particular

movement. The resistance offered by the instrument is an accommodating resistance,

which is designed to match the force generated by the muscle (p.436). Elbow flexion and

4

extension were performed on the CSMi Humac Norm Testing and Rehabilitation System

with right side elbow

Torque

Torque is the tendency of a force to rotate an object about an axis. Torque reported in

this study is a parameter reflects the tendency of a force produced by subject’s arm muscles

when performing elbow flexion and extension to rotate the crank. Since the length of lever

arm keeps constant and the magnitude of torque equals to the value that magnitude of force

applied times magnitude of length of lever arm. So the magnitude (value) of torque can

indirectly reflect the magnitude (value) of force output produced by the arm muscles.

Work

Work is defined as the amount of energy transferred by a force in physics. The work

report in this study reflects the amount of energy transferred by the force the subject

produced to the dynamometer. Since the work value keeps increasing during one repetition

in elbow flexion or extension, it is easier for subjects to understand so that the work report

was captured to produce visual feedback after edited.

University Male Students

University in this study is defined as the students in institutions of tertiary education

such as universities. These student sample subjects were all undergraduate male students in

Hong Kong Baptist University (aged 19 to 25).

Delimitations

The study was delimited to the following:

5

1. The participants of the study were delimited to university male undergraduate

students aged between 19 to 25 years old who major in Physical Education and

Recreation Management.

2. 30 students were selected as sample subjects. All the subjects were from Hong

Kong Baptist University.

3. The tests were conducted in the laboratory (Dr. Stephen Hui Research Center for

Physical Recreation and Wellness in Hong Kong Baptist University) in three

separate days.

Limitations

The study was limited by the following factors:

1. Due to the small sample size (N=30), the result of this study could not produce a

good generalization.

2. The participants’ attitude toward the test might affect the result of the study.

3. Although the three testing days were separated with minimum of three days, the

learning effect may exist.

4. The manipulated irrationally underrated and fading real-time work report may not

be vivid enough to effectively alter the physiology condition of the subject.

5. The manipulated irrationally overrated and increasing real-time work report may

not be vivid enough to effectively alter the physiology condition of the subject.

6. There were eight repetitions of elbow flexion and extension (trial set) functioned as

warming-up assigned before the maximum-effort set. The fatigue and energy loss

6

due to the trial set were uncontrollable.

7. The physical training and the life style of the subjects among the testing days were

uncontrollable.

Significance of Study

Few studies on the current topic were conducted before. So the efficacy of visual

feedback was usually ignored by general population when exercise. For example, it is

common in resistance weight training that the athletes fail to exert maximum strength due

to various reasons. This may reduce the stimulation to the target muscle and therefore

reduce the effect of weight training. Especially for low-repetition-rate and

high-peak-intensity weight training, whether the muscles contract then reach maximum

peak strength directly correlates to the muscular strength gaining and muscle hypertrophy.

A vivid manipulated visual arousal may help athletes to exert maximally themselves to

achieve better training result. Thus this study not only evaluated how significant the effect

of a visual feedback could be, but also provided an alternative training method for both

trainer and athletes as the virtual reality technology develops. Besides regular training, a

visual feedback may be further applied to sport game or competition especially in

non-confrontational sports such as weight lifting.

7

Chapter 2

REVIEW OF LITERATURE

The review of literature was mainly divided into four sections: (a) concurrent studies

on the effect of visual feedback on sport performance; (b) biofeedback applications in

exercise science and physical education; (c) application of isokinetic dynamometer in

exercise science; and (d) summary.

Concurrent Studies on the Efficacy of Visual Feedback on Sport Performance

Jung and Hallbeck (2004) conducted a research to quantify the magnitude of the

influence of the effects of instruction type, verbal encouragement, and visual feedback on

static strength and to verify the applicability of the Caldwell Regimen to grip strength

measurement. Twenty-one male students participated in the study that employed an

isokinetic wrist dynamometer to measure handgrip strength. The results revealed that these

three factors had significant positive effects on static grip strength, peak grip strength and

time to reach the maximal strength.

Campenella, Mattacola, and Kimura (2000) indicated that the use of visual and

combined visual and verbal feedback increased quadriceps and hamstrings force

production when compared to the control condition where no feedback was provided. In

their study, fifteen males and 15 females (age = 25.4 \pm 2.4 yrs, wt = 76.6 \pm 16.5 kg, ht

= 173.61 \pm 9.5 cm) subjects were performed on the Biodex B-2000 isokinetic

dynamometer in three sessions, separated by 7 to 14 days. Subjects tested under the

8

following conditions: (a) visual feedback, (b) verbal encouragement, (c) combined visual

feedback and verbal encouragement, and (d) no feedback (control). The authors found that

examination of quadriceps force production revealed that subjects generated greater peak

torque when visual feedback was provided than when verbal encouragement or no

feedback were provided. Similarly, quadriceps force production was greater when

combined visual feedback and verbal encouragement was provided than when verbal

encouragement or no feedback were provided (p<0.05). Examination of hamstrings force

production revealed that subjects generated greater peak torque when combined visual

feedback and verbal encouragement was provided than when verbal encouragement and no

feedback were provided. Additionally, hamstrings force production was greater when

visual feedback was provided than when no feedback was provided (p<0.05).

In another study conducted by Gallagher, McClure, McGuigan, Crothers, and

Browning (1999), virtual reality was indicated to effectively enhance hand-eye

coordination of novice endoscopic surgeons. Virtual reality is a kind of visual feedback

because the virtual reality interacts with people and gives feedbacks. In the study, sixteen

participants with no experience of endoscopy were required to make multiple defined

incisions under laparoscopic laboratory conditions within 2-minute periods. Half of the

subjects were randomized to receive initial training on the Minimally Invasive Surgical

Trainer, Virtual Reality (MIST VR) computer program. The result was participants with

MIST VR traing made significantly more correct incisions (P = 0.0001) than the control

group on test trial 1, and even after extended practice by both groups (P = 0.0001). They

9

were also significantly more likely to actively use both hands to perform the endoscopic

evaluation task (P = 0.01). Although this study was about medical science, eye-hand

coordination was also a critical characteristic in some sports.

Sihvonen, Sipilä, and Era (2004) indicated that balance training based on visual

feedback improves the balance control in frail elderly women living in residential care,

also enhancing the performance of functional balancing tasks relevant to daily living. They

studied on elderly women of two residential care facilities who were randomized to an

exercise group (EG, n = 20) and to a control group (CG, n = 7). The EG participated in

training sessions three times/week for 4 weeks. The exercises were carried out with a

computerized force platform with visual feedback screen. The dimensions of balance

function studied were standing body sway, dynamic weight shifting, and Berg Balance

Scale performance. The result was the EG showed significant improvement in balance

functions. The performance time in dynamic balance tests improved on average by 35.9%

compared with a 0.6% increase in the CG (p = 0.025–0.193). The performance distance in

these tests decreased on average by 28.2% in the EG as compared with a 9.8% decrease

seen in the CG. The Berg Balance Scale performance improved by 6.9% compared with a

0.7% increase in the CG (p = 0.003). The standing balance tests in the more demanding

standing positions showed improvements in the EG, whereas similar changes in the CG

were not found.

Besides the well studied performance enhancement achieved by visual feedback

tends to during an isokinetic test, the time frame over which visual feedback remains

10

advantageous has been studied by Kim and Kramer (1997). They found that the

effectiveness of visual feedback tended to decrease over the first three occasions,

suggesting that visual feedback may not be as advantageous once a skill is well learned.

Manipulated visual feedback is well applied in motor learning. Elliott and Allard

(2006) conducted three experiments which were target-pointing task. In Experiment One,

subjects moved a stylus to a target 20 cm away with movement times of approximately 225

msec. Visual feedback was manipulated by leaving the room lights on over the whole

course of the movement or extinguishing the lights upon movement initiation, while prior

knowledge about feedback availability was manipulated by blocking or randomizing

feedback. Subjects exhibited less radial error in the lights-on/blocked condition than in the

other three conditions. In Experiment Two, when subjects were forced to use vision by a

laterally displacing prism, it was found that they benefited from the presence of visual

feedback regardless of feedback uncertainty even when moving very rapidly (e.g. less than

190 msec). In Experiment Three, subjects pointed with and without a prism over a wide

variety of movement times. Subjects benefited from vision much earlier in the prism

condition. Subjects seem able to use vision rapidly to modify aiming movements but may

do so only when the visual information is predictably available and/or yields an error large

enough to detect early enough to correct. Their major finding is subjects seem able to use

vision rapidly to modify aiming movements but may do so only when the visual

information is predictably available and/or yields an error large enough to detect early

enough to correct.

11

Another research in motor learning, several "peg-in-hole"-type telemanipulation tasks

were conducted Massimino and Sheridan (1994), each of six human test subjects used a

master/slave manipulator during two experimental sessions. In one session the subjects

performed the tasks with direct vision, where sub tended visual angle, force feedback, task

difficulty, and the interaction of subtended visual angle and force feedback made

significant differences in task completion times. During the other session the tasks were

performed using a video monitor for visual feedback, and video frame rate, force feedback,

task difficulty, and the interaction of frame rate and force feedback were found to make

significant differences in task times. An analysis between the direct and video viewing

environments showed that apart from subtended visual angle and reduced frame rate, the

video medium itself did not significantly affect task times relative to direct viewing.

Biofeedback Applications in Exercise Science and Physical Education

Collins (2002) concluded that biofeedback is an increasingly common and extremely

useful tool for applied sport psychologists. A major application for biofeedback is detecting

and helping in the management of psychophysiological arousal, especially overarousal. He

added that there were a wide variety of indices that can be examined in sport

psychophysiology, and almost all of these can be effectively employed in biofeedback

settings. Collins also concluded that the main physiological processes commonly

associated with overarousal within the field of biofeedback include skeletal muscle tension,

peripheral vasoconstriction (smooth muscle activity), and electrodermal activity. These

three (especially the first two) are the most common biofeedback modalities. “Biofeedback

12

modalities” refers to the various types of instrumentation used for physiological signal

recording and for feedback. Several biofeedback ,modalities have been used in sport, such

as the measurement of muscle tension by electromyography (muscle feedback, EMG), the

measurement of peripheral skin temperature as an index of peripheral blood flow (thermal

feedback, often referred to as “temperature,” Temp), the measurement of electrodermal or

sweat gland activity (electrodermal feedback, EDA), the measurement of the brain’s

electrical activity (electroencephalographic feedback, EEG), the measurement of heart

activity by electrocardiography, including heart rate. Among these modalities, biofeedback

training with EMG, EDA, and HR (recently with EEG) has been used more intensively to

improve athletes’ performance via psychoregulation in various sports disciplines… While

the interest of biofeedback researchers in sport has recently shifted somewhat towards the

identification of psychological conditions associated with better performance, particularly

in closed skill sports, the modification of athletes’ arousal states via biofeedback is still of

great interest to coaches, athletes, and applied sport psychologists (Blumenstein, 2002)

Schwartz and Montgomery (2003) introduced that biofeedback and applied

psychophysiology constitute a multidisciplinary and heterogeneous field of many

professional disciplines and types of applications. Educational and training opportunities in

the field range from courses at university and individual workshops to comprehensive

biofeedback training programs.

Vernon (2005) reported that there have been many claims regarding the possibilities

of performance enhancement training. The aim of such training is for an individual to

13

complete a specific function or task with fewer errors and greater efficiency, resulting in a

more positive outcome. The present review examined evidence from neurofeedback

training studies to enhance performance in a particular area.

Besides fewer errors and greater efficiency, biofeedback is used to reduce the

psychological stress, so that the performance is enhanced. Blumenstein (2002) concluded

that research findings in the field of sport behavior and psychophysiology of exercise

indicate that psychological stress during training and competition can be reduced by

biofeedback training, and thus performance in different sport disciplines can be enhanced.

A very similar study was conducted by Cohen, Richardson, Klebez, Febbo, and

Tucker (2001). They studied on the effects of schedules of reinforcement on an EMG

response maintained by biofeedback. The biofeedback in this study was aiming to enhance

the forearm muscle tension. Because the study was the first attempt to compare the five

basic schedules of reinforcement (i.e., continuous reinforcement (CRF), variable interval

(VI), fixed interval (FI), variable ratio (VR), and fixed ratio (FR)) using the same

experimental procedures, only small values of each schedule were studied in order to

provide fairly comparable rates of reinforcement (feedback) under each of the four

intermittent schedules. But still, some of the data are consistent with the

partial-reinforcement-extinction effect.

Application of Isokinetic Dynamometer in Exercise Science

Isokinetic dynamometer is widely used in exercise science especially musle training

and rehabilitation. Wrigley and Strauss (2000) stated that isokinetic dynamometer can be

14

performed under a range of conditions - of angular velocity, positioning, range of motion,

contraction mode, movement sequence, and so on - from which a wide range of

measurement parameters can be derived.

CSMi Humac Norm Testing and Rehabilitation System, the dynamometer used in

this study, adopted proven mechanical design of the CYBEX NORM (CSMi Medical

Solution, 2005).

Bircan et al. (2002) conducted a study to investigate whether electrical stimulation is

effective in improving quadriceps strength in healthy subjects and to compare interferential

and low-frequency current in terms of the effects on quadriceps strength and perceived

discomfort by using an isokinetic dynamometer. Thirty medical faculty students, divided

into three groups, participated in the study. Group A received electrical stimulation with

bipolar interferential current while group B received electrical stimulation with

low-frequency current (symmetrical biphasic). Group C served as the control group.

Electrical stimulation was given for 15 minutes, five days a week for three weeks, at a

maximally tolerated intensity with the knee fully extended in the sitting position. Before

and after the study, quadriceps strength was measured with a Cybex dynamometer

isokinetically at the angular velocities of 60°/s and 120°/s. The perceived discomfort

experienced with each type of electrical stimulation was quantified by the use of a visual

analogue scale (VAS). Statistically signicant increase in isokinetic strength was observed

after training in group A and group B. Increase in strength did not differ between the

stimulation groups. No signicant change in strength occurred in group C. Perceived

15

discomfort by the stimulation groups was not signicantly different. The study indicated

both interferential and low-frequency currents can be used in strength training with the

parameters used in this study.

In another study conducted by Larivière, Gagnon, Arsenault, Gravel, and Loisel

(2005), the isokinetic dynamometer was used to assess the electromyographic activity

imbalances between contralateral back muscles. Healthy controls (n = 34) and chronic low

back pain subjects (n = 55) stood in a dynamometer measuring the principal (extension)

and coupled (lateral bending, axial rotation) L5/S1 moments during isometric trunk

extension efforts. The results showed that back pain subjects did not produce higher

coupled moments than controls. Providing feedback of the axial rotation moment to correct

asymmetric efforts during the task did not reduce EMG contralateral imbalances, except

for some extreme cases. Normalized EMG imbalance parameters remain relatively

constant between 40% and 80% of the maximal voluntary contraction. The reliability of

EMG imbalance parameters was moderate, at best. Finally, neither low back status nor pain

location had an effect on EMG contralateral imbalances. We conclude that the clinical

relevance of EMG contralateral imbalances of back muscles remains to be established.

Summary

The above review of literature introduced various studies on the effect of visual

feedback on sport performance, different biofeedback applications in exercise science and

physical education and some applications of isokinetic dynamometer in exercise science.

The visual feedback which enhances sport performance in concurrent study was usually

16

without manipulation. For those studies about visual biofeedback conducted in both

athletic and clinical realms, most of those studies were intervened by apparatus such as

EMG or EEG. Various research designs of visual biofeedback studies influenced this study

greatly. The idea, overarousal is somewhat a kind of manipulated feedback. However the

visualized synchronous visualized reports produced by isokinetic dynamometer were

seldom adopted. Thanks to its computer-based operating system, CSMi dynamometer

provides computer-based graph report which is easy for further treatment. Last but not

least, it may involve some ethical problems and the problems will be discussed in chapter

5.

17

Chapter 3

METHOD

This study was to assess the effect of visual feedback aroused by manipulated

real-time report on muscle force output in university male students. The data was obtained

from subjects’ performing elbow flexions and extensions. The experiment of the study

consisted of three testing sessions: (a) VCS, (b) Pre-test, and (c) Post-test. In each testing

session, there was a Trial set followed by resting period and Maximum-Effort set for the

subject to perform. Random sampling and video editing was conducted after Pre-test. The

method comprised in this study was presented in the following sections: (a) subjects, (b)

testing apparatus, (c) pilot testing, (f) procedure, and (g) method of analysis.

Subjects

Thirty male university students aged between 19 and 25 from the Hong Kong Baptist

University were invited to take part in this study. All subjects were free of any

cardiopulmonary or respiratory dysfunction. The health status of subjects was ascertained

by the Physical Activity Readiness Questionnaire (PAR-Q) (see Appendix A). Each of the

subjects was provided informed written consent prior to the test (see Appendix B). The

subjects were assigned into three groups evenly: Control Group (CG), Experimental Group

of Overrated Report (EGO) and Experimental Group of Underrated Report (EGU). There

were 10 subjects in each group. The group assignment was conducted after Pre-test period.

18

Testing Apparatus

The Apparatus adopted in this study included an isokinetic dynamometer with its

computer system and three computer software.

The isokinetic dynamometer, CSMi Humac Norm Testing and Rehabilitation System

(CSMi, Stoughton, MA, USA) was utilized in this study. The system includes the

dynamometer, the computer, and the Humac software. Subjects performed right-side elbow

flexion and extension on the seat of the dynamometer. Eight repetitions of moderate-to-low

intensity elbow flexion and extension was assigned in Trial set which was assigned for

warming up before the Maximum-Effort set in VCS. However only four repetitions were

assigned in Pre-test and Post-test Trial sets. The reason was eight repetitions may probably

limit the performance of Maximum-Effort set in which eight Repetition Maximums (RMs)

were assigned. Since eight RMs exercise was related to both absolute muscle strength and

muscle endurance, prolonged warm-up may consume energy though only a little was used

up during eight repetitions. A beep was given when Trial set had been done. The computer

recorded data when Maximum-Effort sets and displayed the report during both Trial and

Maximum-Effort sets. Besides used as warming-up the target muscles, Trial set was used

to check the ergonomic setting of the machine before the maximum-effort test.

The computer was set to Exercise mode in Video Capturing Session (VCS) rather

than Test mode because the default format of Exercise report is a bar chart while that of

Test mode is a line chart. In the bar chart, the bar of each repetition is isolated (see Figure 1)

rather than overlapped graph which produced by line chart (see Figure 2). What’s more, the

19

bar chart keeps increasing until the rotating arm reached full range in each repetition,

which is suitable to produce the visual feedback, and therefore it was applied and captured

in VCS. By contrast, the line of Test mode (line chart) vibrates and unstable (see Figure 2).

However Test mode can provide a more detailed report so that it was used in Pre-test and

Post-test.

20

Figure 1. Sample of Work Report*

* The height of bars kept relatively stable. The computer program adjusts the unit on Y

axis into appropriate scale timely, and therefore the first bar in Extension was filtered

Figure 2. Sample Line-Chart

21

The three computer software used in the study is: (a) Snagit 9 (TechSmith, Okemos,

MI, USA), (b) Windows Movie Maker (Microsoft, Redmond, WA, USA), (c) Nero Media

Player (Nero, Karlsbad, Germany). Snagit 9 was used to capture the video of dynamic

work value report displayed by computer in VCS. This report was a bar chart which

represented the work value of elbow flexion and extension. Some of the captured movie

will be further edited into manipulated but vivid video by using Windows Movie Maker.

During Post-test, the manipulated video was played with Nero Media Player. The detail of

video editing is described in Procedure section.

Pilot Testing

There were ten university students (other than the subjects described above)

involved in the pilot testing. Several problems were observed during this testing, such as

the conflict between computer software which resulted in the failure to output report when

capturing the video simultaneously. Thus the video capture and report producing were

separated into two isolated test sessions. Other problems emerged were all solved before

the later experiment.

Procedure

The subjects were told to avoid high-intensity strength training two days prior to first

testing as well as during the whole testing period. The entire experiment including VCS,

Pre-test, and Post-test were conducted in the Dr. Stephen Hui Research Center for Physical

Recreation and Wellness in Hong Kong Baptist University, with the temperature and

relative humidity at 22 degree Celsius and 70% respectively.

22

As mentioned above, the experiment included three sessions: VCS, Pre-test, and

Post-test. A minimum of three days were required between two tests to minimize the

learning effect. The three tests were the same in the following procedure:

Common Procedure

Firstly, the subject was required to complete a written consent form and Par-Q

(Appendix B) form to ensure his suitability and readiness for the testing. Furthermore the

subjects were given a brief introduction about the test and instruction about its procedure.

Secondly, the machine had to be set. The isokinetic dynamometer was set into the

elbow flexion/extension mode with Elbow/Shoulder Adapter parts (see Figure 3). The

subject kept to a supine position on the seat of the dynamometer. Seatbelts for trunk and

legs which attached to the machine were fastened around the subject so that the subject can

hold his body and minimize unnecessary trunk rotation when performing maximum-effort

elbow flexion and extension. Once the optimal ergonomic setting (e.g. seat position and

rotation head position) and the setting of the adjustable crank for each subject’s arm action

was achieved, all settings were recorded, individualized and pre-set for each subsequent

test.

23

Figure 3. Ergonomic Setting

Photo retrieved from http://www.csmisolutions.com

24

Thirdly, the subject then initiated exercise. Each subject was assigned to perform

eight repetitions of moderate-to-low intensity trial (warming-up) elbow flexions and

extensions on the machine (only four repetitions in Pre-test and Post-test, the reason was

elaborated in previous section). They were provided eight-second rest right after this trial.

After the rest, the technician checked the ergonomic setting again and asked the subject for

any problem. Afterwards subject performed one set (eight RMs) of maximum-effort elbow

flexion and extension. The flexion and extension must be performed with full range of

motion, which means the subject must drag the handle until hitting both sides’ Range of

Motion Stop (see Figure4, “Adjustable Range of Motion Stops”). No information about the

real-time report or video capturing was presented during VCS and Pre-test. During this

high-intensity exercise, the subject was advised to grab the handgrip attached to the seat

using his left hand. Screaming when exerting force was allowed.

25

Figure 4. CSMi Humac Norm Testing and Rehabilitation System

Figure 5. Flow Chart of Entire Experiment

26

Figure 5 shows the flow of the entire experiment. The following content of this

section is about the differences among VCSs, Pre-test and Post-test as well as the detailed

operation to edit video as well as grouping and random sampling.

Video Capturing Session

There was no special operation during trial and rest. During the subject was resting,

the technician ran the Snagit 9 software to prepare video capturing. Once the technician

initiated the video capturing, the subject was given the signal to begin elbow movement.

There was no verbal feedback or encouragement given during the entire eight RMs. Once

the repetitions completed, a beep was given. The technician then stopped the video

capturing and unfastened the seat belt for trunk to let subject cool-down and relax. Subject

can loosen the belt for legs by himself. As followed, technician provided positive verbal

feedback to the subject about his performance, ask him if any problems, and appoint the

time slot for the next test. The captured video was saved in the computer for further

procedure.

Pre-test

The test procedure was the same as Common Procedure except that the trial was set

to four repetitions and the dynamometer was set to Test mode for obtaining a more detailed

report. The report contains the data of maximum-effort elbow flexion and extension peak

torque graphs and average peak torque value.

Grouping and Random Sampling

With their peak torque data obtained in Pre-test, subjects were sorted by a

27

descending order of their sum up value of average peak torque (flexion) and average peak

torque (extension), which was named as Pre:SUM in later data analysis. Then they were

stratified into ten strata in which three subjects were stratified in each stratum and they

were further random sampled into CG, EGO, and EGU within their own stratum.

Video Editing

The captured video was edit by Windows Media Maker. Useless head and tail part of

this video were precisely cut up so that once strike the keyboard, the work bar on the

screen initiated rising immediately. This can promise an optimal synchronization

theoretically. Then these treated videos were further edited in different ways by group.

There was no manipulation on the video of CG.

The video of the subjects in EGO was manipulated into a video where the last four

bars representing the maximum-effort flexions and extensions work value were edit into

irrationally high and increasing bars (see Figure 6). This was achieved by using Windows

Movie Maker. The method was to substitute the manipulated video (a video in which last

four intentionally increasing bars were produced by the technician himself) for the last part

of original video at the moment the fourth bar stopped rising and the fifth bar initiated its

rising. The first four bars were kept original because they functioned for convincing the

subject that the “fake” video was a true one.

28

Figure 6. Edited Video for EGO

Figure 7. Edited Video for EGU

29

The video of the subjects in EGU was manipulated into a video where the last four

bars representing the maximum-effort flexions and extensions work value were edit into

irrationally low and fading bars (see Figure 7). The first four bars were kept original

because they functioned for convincing the subject that the “fake” video was a true one.

All these videos would be played in Post-test Session.

Post-test

Minimum of three days after the Pre-test, subjects participated in the last test, the

Post-test Session. Before testing, the technician told the subject that he was required to

perform four repetition trial elbow flexions and extensions, and at the same time, he must

watch the screen (see Figure 8) which displayed torque report in line chart. The technician

explained that the line chart displayed during trial set was a torque report and used for

subject being familiar with the both ergonomic setting and body posture with head rotated

when flexing and extending elbow. After the trial, eight-second rest was provided.

30

Figure 8. Subject’s Posture during Post-test

31

The technician then told the subject that he was going to perform maximum-effort

elbow flexions and extensions (eight RMs) with watching the screen. The subject was told

that the screen would display his real-time work report which was in the bar chart form,

but in fact what the technician would play was a manipulated video mentioned above.

Then the technician explained to the subject that the bar represented the work value of his

elbow movement. The higher the bar rises, the more work done by the subject’s arm

muscles. The technician specially emphasized that the subject was wished to produce as

high bar as possible because the set was a maximum-effort one. Furthermore, the

mechanism, the computer would automatically adjust the unit on Y axis for optimal display

as well as the consequence that all bars may be squeezed or elongated together after

adjusted, were explained. This was important because at the very beginning of the

manipulated part in Experimental Groups’ video, the ratio of Y-axis would alter and all the

bars may be elongated or squeezed. However it should be noted that the unit

auto-adjustment actually was not the reason why the bars transformed at the fifth

repetition.

After instruction, the trial began. During the following eight-second rest, the

technician rotated the computer screen to the direction that the subject can not see what

was going on the screen. Then the technician prepared for playing the manipulated video

by using Nero Media Player with full screen. The instruction about the maximum-effort set

mentioned in Video Captured Session was repeated to the subject. The only extra

instruction was that the subject had to watch the screen from start to the end and the

32

technician would rotate the screen to the direction subject can watch clearly a short

moment after he started the video playing. After ensured no problems existed, the

technician gave a signal to the subject to initiate the elbow flexion. At the moment the

machine arm hit the stop, the technician strike the keyboard gently to play the video and

then rotate to the subject. Similarly, no verbal feedback or encouragement was presented.

After finishing the entire eight RMs, the subject was released from the belt and advised to

cool-down himself. The data of Post-test maximum-effort elbow flexions and extensions

average peak torques were soon obtained and printed out. At last, the subject was told the

truth and the whole experimental design. Some first-step analysis after quick glance at the

raw data was also provided. The summed-up value of average peak torque in extension and

flexion was named as Post:SUM. Another variance, %Change was defined as Post:SUM

divided by Pre:SUM then minus 1. These variances will be analyzed in Chapter 4.

The tested movement (elbow flexion and extension) was set as an isokinetic

contraction in the system with the range of motion fixed both in Pre-tests and Post-test, the

pace of bicep curl were almost the same in Post-test compared with in Pre-test. This

synchronization between Post-test physical elbow movement and the manipulated bar

vibration rhythm was based on the condition when both initiated simultaneously (i.e. the

technician click the button just at the moment the machine arm hit the Range of Motion

Stop while the subject performing the first elbow flexion). This technique need to be

practiced but is not very hard to handle.

33

Method of Analysis

Statistical Package for Social Science (SPSS) for window14.0 version computer

program was used for all the statistical calculations. The mean values of average peak

torque such as Pre: SUM and Post: SUM in each group during Pre-test and Post-test

computed. Contrast test for One-Way ANOVA between CG and two Experimental Groups’

%Change was conducted to compare the mean peak torque change differences, with

significance level set at 0.05. To promise the reliability and validity of the study, Contrast

tests for One-Way ANOVA between different groups’ Pre:SUM and Post:SUM were also

conducted.

34

Chapter 4

ANALYSIS OF DATA

Results

Twenty-nine subjects completed the entire experiment (i.e. VCS, Pre-test, and

Post-test). The test on twenty-nine subjects generated their reports about average peak

torques and % change from Pre-test to Post-test, in which eight repetitions of

maximum-effort elbow flexions and extensions were measured. These subjects did not

know what they watched on the monitor during Post-test maximum-effort session was

manipulated. One subject in the EGU was able to complete all sessions of the experiment,

but the system failed to output its Post-test report. Since this subject was told about the

experiment design right after Post-test, it was not suitable for him to repeat the Post-test in

order to obtain a report, so his data was not included in this study. One of the subject in

EGO, who achieved a significant increase (increased by 40.4% of the number of Pre-test)

in extension average peak torque but a slight decrease in flexion, reported that he did

several sets of high intensity push-up trainings a few days before Post-test. Another subject

in EGO who achieved significant increase in both flexion and extension average peak

torques (increased by 39.7% of the sum of flexion and extension average peak torques)

during Posttest reported that the ergonomic setting of dynamometer machine in Pre-test

was not as comfortable as in Post-test. These cases may be considered as threats to the

experimental result but their data was still analyzed together. No other adverse effect from

35

the experiment sessions was observed or reported by the subjects.

Figure 9 is a sample of peak torque report. A peak consisting series of tiny crests

represents the torque of one full-range extension or flexion over time. The study compares

different groups’ average peak torque shown in the cell “Peak Torque (Newton-Meters

Average Value)” below the graph. Body weight was not involved in this study.

Figure 9. Sample Output Work Report Produced by Dynamometer

36

Table 1 shows the result of Pre-test. This result represents all subjects’ performance

and the result of grouping. The subjects were listed in descending order in reference of

their Sum value. Extension (Flexion) is the average peak torque value of eight

maximum-effort elbow extensions (flexions) during the Pre-test maximum-effort set. Sum

is the sum-up value of Extension with Flexion.

37

Table 1

The average peak torque of eight-RM elbow flexion and extension during Pre-test by

descending order in reference to Sum and the result of grouping

(N=30)

Pre-test Subject ID Group (a)

Extension Flexion Sum (b) 2b Under 61 49 110 4e Over 58 49 107 1d Control 52 54 106 5b Control 50 54 104 5g Under 60 43 103 6c Over 49 45 94 6e Over 47 47 94 2a Control 45 46 91 6f Under 41 49 90 6d Over 43 46 89 5d Control 47 41 88 2d Under 49 38 87 3b Under 45 41 86 3a Over 43 41 84 4b Control 39 45 84 5f Control 45 37 82 2c Under 43 38 81 6a Over 40 40 80 5a Under 39 39 78 1e Control 41 35 76 5c Over 39 37 76 2e Over 34 38 72 1b Under 35 35 70 1c Control 35 34 69 4d Over 35 34 69 1a Under 33 35 68 4a Control 34 34 68 6b Control 28 34 62

38

5e Over 26 28 54 4c Under 23 30 53

a Control = CG; Over = EGO; Under = EGU.

b Sum = Extension + Flexion

39

Table 2 shows the descriptive statistic for Pre-test average peak torques and their

maximum, minimum, mean and standard deviation values were included. This result

represents all subjects’ performance without grouping. Similar to what mentioned above,

value of Pre-test: Extension (Flexion) is the average peak torque values of eight

maximum-effort elbow extensions (flexions). Value of Pre-test: Sum is the sum-up values

of Pre-test: Extension and Pre-test: Flexion.

Table 2

Descriptive statistic for Pre-test average peak torque

(N=30)

N Minimum Maximum Mean Std. Deviation

Pre-test: Extension 30 23.00 61.00 41.7667 9.36495

Pre-test: Flexion 30 28.00 54.00 40.5000 6.70949

Pre-test: Sum 30 53.00 110.00 82.2667 15.13601

Valid N (listwise) 30

40

Table 3 shows the result of Post-test. The result of one subject was failed to produce

after Post-test’s testing, so there were only 29 subjects’ result listed in the table. The

subjects were also listed in descending order in reference to Sum value.

41

Table 3

The average peak torque of eight-RM elbow flexion and extension during Post-test by

descending order in reference to Sum and the result of grouping

(N=29)

Post-test Subject

ID Group (a)

Extension Flexion Sum(b)

1d Control 58 65 123

2d Under 69 53 122

2b Under 62 49 111

6e Over 66 45 111

2a Control 58 50 108

4e Over 61 47 108

5g Under 60 47 107

5b Control 50 56 106

2c Under 56 46 102

6a Over 52 50 102

3a Over 52 47 99

6f Under 46 53 99

5f Control 54 43 97

6c Over 54 43 97

5d Control 46 49 95

2e Over 52 39 91

6d Over 43 46 89

1c Control 42 45 87

1e Control 43 42 85

4b Control 39 45 84

3b Under 43 39 82

5c Over 43 39 82

4a Control 47 34 81

5e Over 39 38 77

1b Under 35 38 73

6b Control 31 39 70

1a Under 30 39 69

4d Over 33 35 68

42

4c Under 34 30 64

a Control = CG; Over = EGO; Under = EGU.

b Sum = Extension + Flexion

43

Table 4 shows the descriptive statistic for Post-test average peak torques and their

maximum, minimum, mean and standard deviation values were included. This result

represents all subjects’ performance after grouping under different type of visual feedback.

Table 4

Descriptive statistic for Post-test average peak torque

(N=29)

N Minimum Maximum Mean Std. Deviation

Post-test: Extension 29 30.00 69.00 48.2069 10.64149

Post-test: Flexion 29 30.00 65.00 44.5172 7.26843

Post-test: Sum 29 64.00 123.00 92.7241 16.13093

Valid N (listwise) 29

44

Table 5 shows the descriptive statistic for Pre-test: Sum and Post-test: Sum. This

comparison represents all subjects’ performance without grouping. Improvement is the

value of subtract Pre-test: Sum from Post-test: Sum. % Change is the value of Post-test:

Sum divided by Pre-test: Sum, then minus 1. Although being not the purpose of the study,

this table indicated that the mean value of Post-test average peak torques were obviously

higher than mean value of Pre-test average peak torque. Only a few subjects (n=2 out of

total N=29) were reported lower value of Post-test average peak torque of summed-up

extension and flexion than that of Pre-test.

Table 5

Comparison between Pre-test Sum and Post-test Sum of Average Peak Torques

(N=29)

N Minimum Maximum Mean Std. Deviation

Pre-test: Sum 29 53.00 110.00 82.4138 15.38208

Post-test: Sum 29 64.00 123.00 92.7241 16.13093

Improvement 29 -4.00 35.00 10.3103 9.66253

% Change 29 95.30 142.60 113.4793 13.06630

Valid N (listwise) 29

45

Table 6 shows the result of One-Way ANOVA comparing the mean values of %

change (the value of Post-test: Sum divided by Pre-test: Sum, then minus 1) among CG

(labeled as “control”) and two Experimental Groups (Overrated Report labeled as “over”

and Underrated Report labeled as “under”). Table 7 is the result of the Contrast test for

One-Way ANOVA. The result of analysis indicated no significant difference in average

peak torque value between CG and EGO as well as CG and EGU at the significant level of

0.05. Thus the hypothesis, the value of average peak torque of elbow flexion and extension

would not be enhanced by the visual feedback produced by overrated report in the

university male students, was accepted.

46

Table 6

Result of One-Way ANOVA on the Pre-test: Sum, Post-test: Sum, and % Change among

three groups

(N=29)

Category SS df MS F Sig. Between Groups 22.55 2.00 11.27 0.04 0.96*Within Groups 6602.49 26.00 253.94

Pre-test: Sum (a)

Total 6625.03 28.00 Between Groups 12.10 2.00 6.05 0.02 0.98*Within Groups 7273.69 26.00 279.76

Post-test: Sum (b)

Total 7285.79 28.00 Between Groups 80.54 2.00 40.27 0.22 0.80*Within Groups 4699.85 26.00 180.76

% Change (c)

Total 4780.39 28.00

a Pre-test: Sum is the summed-up value of Pre-test’s maximum-effort elbow flexion and

extension average peak torque.

B Post-test: Sum is the summed-up value of Post-test’s maximum-effort elbow flexion

and extension average peak torque.

* p<0.05.

47

48

Another statistic, one-tailed independent t-test comparing the mean values of %

Change between CG and Experimental Groups (p < 0.05) were conducted just as a

reference in Appendix E, though t-test is not suitable to apply in this case. In this statistic,

the % Change of EGO is significantly higher than that of CG. Contrarily, there is no

significant different of % Change between EGU and CG. This somewhat obeys the

psychology theory (i.e. reinforcement is more power than punishment in altering humans

behavior).

Discussion

This section contains three issues: (a) discussion about experiment design, reliability,

and validity; (b) discussion on psychophysiological domain; (c) discussion on ethical

issues.

Discussion about Experiment Design and Reliability

The objective of this study was to assess the effect of manipulated visual feedback

on the force output of elbow flexion and extension by observing peak torque. Although

several potential risks may threat the reliability, the experiment was successful in

convincing subjects that the manipulated fake or original torque report video was a

real-time report. The factors threatening the reliability and validity of the study are listed

below:

Individual Differences

Subjects’ individual differences in learning efficiency may affect the reliability of the

experiment. Some subjects were able to handle the technique so as to effectively perform

49

elbow flexion and extension on the isokinetic dynamometer after Pre-test, and then achieve

a much greater work peak output in Post-test than others. In addition, the fact that some

subjects have known isokinetic dynamometer before but some not, may also affected the

reliability. On the other hand, the psychology activity process and the consequent

psychophysiological response during the test, especially Post-test, varies among the

subjects. Although it may affect the reliability, these personal differences did neither

specifically assemble in certain groups nor increase or decrease the significant level jointly.

Further psychophysiology issue is discussed in (b) Discussion on psychophysiological

domain part.

Ergonomic Setting

A suboptimal ergonomic setting of isokinetic dynamometer for certain subject would

hinder his elbow movement and therefore suppress the peak torque. Several subjects

reported after the test that the ergonomic setting was not optimal, but the problem was

minor. Only one subject reported the ergonomic problem was significant and it may

contribute to the significant enhancement of EGO peak torque, which was mentioned in

Result part.

Muscle Training between the Tests

Although subjects were required to cease “overloading or high-intensity” weight

training of arms during the study period to prevent unwanted muscular strength gaining,

there was no precise definition for “overloading or high-intensity” training. Simultaneously,

moderate- to low-intensity regular training of arms may also result in muscular strength

50

gaining in arm muscles and then enhance peak torque value in Post-test more significantly

than those without arm training. One subject in EGO reported that he had worked out

intensively (i.e. push-up) days before the Post-test day, which mentioned in previous

paragraph. This extra training may also contribute to the significant enhancement of peak

torque value.

Overkill in Statistics

CSMi Humac Norm Testing and Rehabilitation System gives the report of average

peak torque value within the entire set (one set contains several repetition). This means the

average peak torque value actually reported the mean value of total eight flexions and eight

extensions in this experiment, in which first four flexions and extensions were not

manipulated and therefore no effect caused by manipulation existed. Although the system

can work out a report with the graph of each single flexion or extension, the statistic

numeric result only contains average peak torque value still for total eight repetitions rather

than for the last four. Thus the result of average peak torque value does not purely imply

the effect of manipulation.

Concentration towards the Monitor

Another risk affecting reliability was the different concentration levels among the

subjects towards the monitor that displayed the report. Some subjects were too

concentrated on elbow movement to miss the process of the bars on the screen. Neglecting

the crucial 5th, 6th or 7th bar would alter the subject’s psychophysiological process since the

visual information was delayed and discounted. Fortunately, after given a briefing about

51

the test, most of the subjects kept watching the screen from begin to the end.

Losing of Synchronization

Although the elbow flexions and extensions were set as isokinetic work out, the

speed of machine arm rotation was not completely stable. The error may amplify over the

repetitions so that last several bars may have presented with quite poor synchronization.

However most of the subjects were not familiar with the reporting system and the duration

was too short to deliberate these minor problems. As a result, no subjects have expressed

doubt of the facticity of the report displayed.

Arm Muscle Strength Gaining due to Pre-test

The arm muscle may probably gain muscular strength even only eight repetitions

were performed during Pre-test since the test required maximum-effort work out. Although

the Pre-test and Post-test day of a subject were separated by some days, potential muscular

gaining was still inevitable, but this problem is minor.

Hawthone Effect

Most of the subjects thought they were attending a training program although they

did not know what training they actually received. As a result, many of the subjects work

harder during Post-test as they knew they were being observed. This factor may not bias

the result but decrease the tendency of achieving a significant difference among groups

since the force output of subjects was supposed to increase regardless of their group under

Hawthone effect.

52

Discussion on Psychophysiological Domain

Although the % Change between groups does not indicate any significant differences,

the result shows that the overrated visual feedback, in which the reported work value was

irrationally high and kept increasing, did enhance the peak torque compared to CG, but the

underrated report inhibited the peak torque. The result of Contrast test for One-Way

ANOVA which involves EGU indicates that irrationally low and fading bars somewhat

inhibit the force produced by the relevant muscles. So the effect of overrated report’s

enhancement is more notable than that of underrated report’s inhibition, by contrast. This

result was completely opposite to what was expected before the testing. Originally subjects

in EGU were expected to have a significantly higher % Change in average peak torque

ratio, because the irrational fading of bar chart was supposed to enrage the subject and then

result in an ultra-level performance in work output. Contrary, subjects in EGO were

expected to have a significantly lower % Change in average peak torque ratio, and the

explanation was that the unexpected increasing of the value of elbow flexion and extension

work would relax the subject from performing outdoing himself. However, the result of

this study among university male students indicated that irrationally high and increasing

bars enhanced the force produced by the relevant muscles though not that significant.

One of the subjects in EGU said that, in fact, they felt strange and were then soon

frustrated, instead of anger during the last several repetitions in Post-test. Probably,

frustration rather than anger was the common emotion when the feedback was underrated.

After the entire experiment, some interviews were conducted to subjects. Most of the

53

subjects in Experimental Group expressed their confusion about the irrational fluctuation

of the last several bars representing the work value in the report displayed. The only

subject in EGU, whose Post-test’s average peak torque was even lower than that of Pre-test,

said that he felt very strange when he saw first several irrational low bars since he had tried

his best, and then he felt frustrated soon during last several repetitions. By contrast, the

subject in EGO said that he felt a little bit confused at the very beginning of manipulated

video was played. After the confusion, he soon attempted to produce an even higher bar.

These explanations are far away from the expectation but are quite reasonable. However

the fact that subjects have not enough time to doubt the facticity of the video is expected.

Interestingly, this research finding actually obeys the psychology theory. In

Skinner’s definition of reinforcement, if the effect of the stimulus is to increase the rate of

emission of the preceding response, by definition the stimulus is a reinforcer, and the

process is called reinforcement. By contrast, the definition of a punishment, if the effect of

the stimulus is to decrease the rate of emission of the preceding response, by definition the

stimulus is a punisher, and the process is called punishment (Barker, 2001).

Smith (2006) introduced the definition of positive reinforcement that presentation of

a positive stimulus increased the likelihood of the behavior will occur in the future under

the same conditions. In this study, the increasing of the bar in representing work value in

the report for subjects in EGO can be regarded as a positive stimulus. Thus the

maximum-effort test process for EGO in fact was a positive reinforcement model. G.

Zimbardo, R. J. Zimbardo, and P. G. Zimbardo (2002) defined that negative punishment is

54

a behavior that followed by the removal of an appetitive stimulus, decreasing the

probability of that behavior. In this study the relatively stable height of bar (see Figure 1)

for subjects in EGU can be classified as appetitive stimulus since a maximum effort output

throughout the entire maximum-effort session was required and the subject would like to

see the last several bars remain a stable height. Similarly the maximum-effort test process

for EGU was a negative punishment model.

Reinforcement is long believed to be more powerful in altering behavior than

punishment in education. Tingstrom, McPhail, and Bolton (2001) summarized that several

studies have investigated the acceptability ratings of different types of alternative

interventions and have generally found that positive intervention is rated more acceptable

than reductive intervention. That is, intervention based primarily on reinforcement is

typically rated more acceptable than intervention based on punishment. (In their study, the

acceptability was assessed as “a function of reported effectiveness of the procedure and the

age of the target child.)

Current study is probably a practical application of above theories, although the

amount or magnitude of the positive reinforcement model and negative punishment model

(how much the video increased or faded) were neither measurable nor equal. Regardless of

the amount or magnitude, the result may indicate reinforcement has more notable effect on

altering muscle physiological condition than punishment. As a study on manipulated visual

feedback, this conclusion may not have optimal generalization. Besides the small sample

size mentioned in Chapter 1, the parameter of manipulated visual feedback varies. This

55

study is mainly about one parameter, the height of bars in the real-time work report, and

therefore the efficacy of manipulated visual feedback needs further studied in various

dimension such as psychophysiology, on its different parameters.

In exercise science and physical education, reinforcement and punishment have also

been widely studied. Smith (2006) mentioned that there is clear evidence that punishment

and criticism can decrease unwanted behaviors. Unfortunately, the evidence is equally

compelling that punishment has certain undesirable side effects that can actually interfere

with what a coach is trying to accomplish. First and foremost is the fact that punishment

works by arousing fear.

Barker and Cliff (2003) concluded that fear of the negative stimulus may initially

inhibit or prevent the athlete from achieving peak performance. But once the player is put

into a relaxed and confident frame of mind and exposed repeatedly to the negative stimulus

in the form of game competition, he can ultimately have a breakthrough game in which he

will overcome his performance anxiety and lock the powerful positive reinforcements

associated with successful play into the desired behavior.

Previous researches in sport psychology successfully analyzed the effect of emotion

on sports performance. Extra research finding of this study (i.e. the psychophysiology

finding) probably implies that the psychological activity can affect the force output of

working muscles instead of a very broad idea such as sports performance.

Discussion on Ethical Issues

During Post-test maximum-effort sets, the subjects were told at first that the video

56

played at mean time was his real-time torque report, but actually not. This design was

aimed to optimize the experiment validity. After explaining the study during debriefing, no

subjects have complained about being deceived.

57

Chapter 5

SUMMARY AND CONCLUSION

Summary of Results

This study was to assess the effect of visual feedback aroused by manipulated

real-time report on muscle force output in university male students. Thirty university male

students participated in the study as subjects and 29 data was obtained at last. The subjects

were asked to perform maximum-effort elbow flexions and extensions on isokinetic

dynamometer after several seconds break behind the trial. There were three test sessions in

the study after several pilot tests. The first test was used to capture the video of real time

report. The second one was a Pre-test which used to obtain the raw data before

manipulation. The last test, Post-test was used to obtain data during manipulation. Subjects

were divided into three groups: CG, EGU, and EGO. Three groups were interfered with

different manipulations in Post-test. CG subjects were given the original report captured in

the first test. EGU was given a manipulated video, where the last four bars which reflect

work value of elbow flexions and extensions in the dynamic report being edited into

irrationally low and fading bars. Contrary, the video played to EGO were edited into

irrationally high and increasing ones. The system recorded the average peak torque of eight

flexions and that of eight extensions. Then the ratio Post-test value over Pre-test value in

different Experimental Groups were compared to that in CG by Contrast test for One-way

ANOVA at a significant level of 0.05. The means of % change in average peak torque were

58

additionally compared by independent t-test just as a reference.

Conclusion

The result indicated that the improvement in average torque value from Pre-test to

Post-test neither in EGO nor in EGU were significantly different from CG. However, the %

Change of EGO was higher than EGU though not significant. Due to various threats to

reliability and validity, the manipulated visual feedback is not significant in altering force

output of target muscle, although the result of t-test implies the overrated visual feedback

can significantly enhance the force output, it is not suitable to use t-test here. In

psychology concepts, the situation in EGO can be identified as positive reinforcement

model; the situation in EGU can be identified as negative punishment model.

Reinforcement is widely accepted to have a stronger ability to alter human behavior than

punishment in education, and the result of this conclusion obeys this theory even in

physiological performance such as muscle contraction. In addition, this study potentially

implied that psychological activity can affect the force output produced by working muscle

in university male students.

Recommendation for Further Studies

Besides prevention of various risks listed in Chapter 4 which would threat the

reliability of the study, several extra recommendations are listed below.

First, more Pre-tests are highly recommended if time allows. With repeated practices,

subjects can learn the technique of how to perform optimal work output inside the

ergonomic environment on isokinetic dynamometer and finally discover their individual

59

optimal ergonomic setting, which may promise the real maximum output during Post-test.

Second, the magnitude of edited irrationally high or low bars should be standardized

and taken into statistic. Current study has no control upon the qualitative parameters of

manipulation on the feedback but only the quantitative parameters. With the magnitude of

manipulation taken into consideration, the result would be more precise and persuasive.

Last but not least, if the computer of the isokinetic dynamometer can calculate only

the mean torque value in manipulated period (i.e. last four repetitions of elbow flexions

and extensions), the result would be more accurate and valid.

60

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65

APPENDIX A

Consent Form to Students (Chinese Version)*

敬啟者:

生理回饋對於力量訓練作用的測試 本人葛力，現就讀於香港浸會大學康樂及體育系三年級，正預備完成上述測試。 本測試存在一定的危險性，但是在我們的嚴密監控下，多數情況下是安全的。本

測試需要採集受試者在 CSMi HUMAC Norm Testing and Rehabilitation System 上做八

次肘屈曲熱身及八次全力的肘屈曲，本測試的後測試（post-test）將于約兩周後進行，

測試內容相同。如有必要，受試者可以隨時揚聲要求終止測試。 如對本問卷有任何諮詢或欲得本研究結果，歡迎聯絡本人葛力，電話 98144997，

獲取有關資料 ◦ 謝謝

日期: 2010 年 2 月 11 日

_________________________________________________________________ 本人______________願意參與這次問卷調查，並得知本人之姓名將被保密 和有

權諮詢研究結果。 _________________ ________________ 簽署 日期

* Since this form was produced before the first testing, it does not reflect the updated

features in later tests or includes wrong information. However all subjects were informed

of the latest and correct information before testing. This note is also applicable to

Appendix B.

66

APPENDIX B

Consent Form to Students (English Version)

Dear fellow students,

The Effect of Biofeedback on Strength Training

I am GE Li, a year 3 student in the Hong Kong Baptist University majoring in

Physical Education and Recreation Management, is now going to complete my course

work on the able mentioned topic.

The test consist certain potential risk, however, under our careful monitoring, it is

safe most of the time. The subject will perform eight repetitions of trial elbow flexion and

extension and eight repetition-maximums of elbow flexion and extension which need

maximum effort. The subject will finish the testing on CSMi HUMAC Norm Testing and

Rehabilitation System. There will be three test sessions in all and two weeks between two

test sessions are required. The subject can require ceasing the test at any time if necessary.

67

Should there be any queries or if you want to get a copy of this research report,

please contact GE Li, telephone: 98144997.

Thank you.

Yours sincerely,

__________________

Date: Feb 11, 2010

_____________________________________________________________________

I, ___________________ understand my involvement of doing this questionnaire is

voluntary, and I have been told that my name will be kept confidential. I have the right to

ask for the completed report.

____________ ____________

Signature Date

68

APPENDIX C

Physical Activity Readiness Questionnaire (Par-Q)

69

APPENDIX D

Post-test Illustrations

Rotate the monitor to the direction the

subject can not see and prepare for

the video playing

Strike the keyboard (Play button)

when the machine arm hit the ROM

stopper during first elbow flexion

Rotate the screen for the subject to

watch during elbow movement

70

APPENDIX E

Two-Tailed Independent T-Test (Reference Only)

Two-Tailed Independent T-Test between CG and EGU

Category F Sig.*

% Change Equal variances assumed 3.450 0.081

Equal variances not assumed

* p < 0.05

Two-Tailed Independent T-Test between CG and EGO

Category F Sig.*

% Change Equal variances assumed 5.641 0.029

Equal variances not assumed

* p<0.05