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
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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.
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
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
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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
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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.
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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
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5e Over 26 28 54 4c Under 23 30 53
a Control = CG; Over = EGO; Under = EGU.
b Sum = Extension + Flexion
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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