THE UNIVERSITY OF HONG KONG LIBRARIES
Hong Kong Collection gift from Hong Kong Sports Development Board
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Preface Taekwondo is a free-fighting, combat sport that is popular in Hong Kong, it is an international sport, with over 18 million participants worldwide, and is one of the new Olympic sports in the Sydney 2000 Games. Taekwondo is well-known for its fast, high and spinning kicks, and good kicking technique is an essential part of the sport. Using biomechanical analysis, Dr Hong and his team studied athletes' kicking technique and then designed a training programme that strengthened the leg muscles used during high-speed kicks. The study was carried out in association with Lok Wah Taekwondo Club and SDB acknowledges the Club's contribution to the study. The Hong Kong Sports Development Board (SDB) commissioned this study as part of its sports science and medicine research programme, and it provides another example of how scientific study can help Hong Kong's athletes improve their training and competitive performance.
Biomechanical Analysis of Taekwondo Kicking Technique, Performance & Training Effects
The study was carried out for SDB by: Dr Youiian Hong (Principal Investigator), Associate Professor, Department of Sports Science and Physical Education, The Chinese University of Hong Kong Leung Hing Kam, Chief Coach and Chairperson of Lok Wah Taekwondo Club Luk Tze Chung, Jim, Department of Sports Science and Physical Education, The Chinese University of Hong Kong SDB Research Report - No. 2 ©SDB, August 2000
FINAL REPORT
For the Project Biomechanical Analysis of Taekwondo Kicking Technique, Performance and Training Effects Submitted to Hong Kong Sports Development Board
By
Youlian Hong, Ph.D., Associate Professor Department of Sports Science and Physical Education The Chinese University of Hong Kong . Leung King Kam, Chief Coach and Chairperson of Lok Wah Taekwondo Club Luk Tze Chung, Jim Department of Sports Science and Physical Education The Chinese University of Hong Kong
Abstract The purpose of this study was to investigate the kicking technique of Hong Kong Taekwondo athletes and to develop a well-designed training protocol to improve the performance of Taekwondo athletes in Hong Kong, A pre- and post-test design was employed in this study to examine the effectiveness of a training protocol that was based on the outcome of the pre-test. For each test session, the Taekwondo frontal attack kicking technique, such as sidekick, pushing kick, slap kick and back kick, was investigated. Kicking performance was video filmed and the muscle activities were recorded by an electromyography (EMG) system. Based on the recorded EMG signals and the EMG signals obtained from measuring the maximum voluntary contraction (MVC) before the test trial, the 4>efcSafege !MVC (%MVC) was derived. The ' /', —
kinematics of each kicking movement ^ece^obj^ined by digitising and analysing the *'*8:i$&' recorded video tapes on a motion analysis system. The results showed that there were significant differences in kicking time among different styles of kicking (p<.001) and different heights of kicking (p<.001). However, there was no significant difference in kicking time between different preparation forms. The front turning kick to the waist level with standing preparation form was significantly faster (0.70 ± .098s) than the other styles of kicking.
However, the one-step sidekick to the head level with
standing preparation form was significantly slower (1.09 ± ,119s) than other styles of kicking. The muscle activity during kicking was significantly different among selected muscles (p<.001). The vastus lateralis and tensor fasciae latae showed significantly higher average activity when compared with other selected muscles. The average muscle activity for the tensor fasciae latae and the vastus lateralis was 133.12 ± 77.55%MVC and 250.44 ± 182.28%MVC, respectively. This value for sartorius, rectus femoris and vastus medialis was 42.33 ± 14.98%MVC, 66.84 ± 31.31%MVC
and 75.98 ± 41.19%MVC, respectively. Muscle activity of hamstrings can be represented by semitendinosus and biceps femoris. The activity level of these two muscles was 43.53 ± 15.43%MVC and 47.14 ± 28.29%MVC, respectively. The isokinetic training protocol was designed with knee concentric extension/flexion at 240deg/s, 20 repetitions in each set, 5 sets for each session, 3 sessions weekly. The isokinetic concentric knee extension peak torque at 240 deg/s showed significant increase from pre- (108.83 ± 16.95 Nm) to post-test (117.83 ± 18.99 Nm) for the training group. It was concluded that isokinetic training at 240 deg/s angular velocity can increase the muscle peak torque of concentric knee extension at that velocity.
Objectives The objective of this study was to investigate the available methods for analysing kicking technique and performance of Taekwondo athletes. By using biomechanical analysis, a systematic measurement of Taekwondo
kicking technique
and
performance could be developed. The results obtained from this study could be used to develop an advanced protocol to improve the kicking technique and performance of Taekwondo athletes in Hong Kong. The ultimate target is to increase the competitive ability of Hong Kong Taekwondo athletes.
Background Taekwondo is one of the popular sports in Hong Kong. Moreover, it will become a formal event in the Sydney 2000 Olympic Games. Therefore, there is a need to place considerable attention on this sport. Taekwondo was originally developed as a fighting art in Korea and has been distributed all over the world. With over 18 million practitioners worldwide, today Taekwondo is generally regarded as the most popular
event of the martial arts. When reviewing the development of Taekwondo in various countries, Mainland China would be a good example, as it has forcibly promoted Taekwondo in the last three years. The aim being to raise the level of Taekwondo in Mainland China to world standard.
Biomechanics methods have been successfully used to improve traditional training methods and athletic performance. Traditional training methods for Taekwondo have been developed for a decade in Hong Kong. However, the scientific study of Taekwondo was lacking. To improve the competitive ability of Hong Kong Taekwondo athletes in world level competition, it is necessary to develop applicable scientific training methods. The systematic and scientific methods that were developed in this study will be useful in evaluating the performance and technique of Taekwondo athletes in Hong Kong.
In this study, a biomechanical method for evaluating Taekwondo kicking technique and performance was developed. The kicking speed, reaction time, and muscle group recruitment for kicking was measured. Taekwondo is a sport that focuses on using appropriate kicking technique. The proper use of the lower limb muscles when kicking is an important factor affecting the overall performance of Taekwondo athletes. Based on the results of the evaluation, a scientific training protocol was developed. The training protocol focused on the kicking speed, force produced and strengthening exercise for the prime muscles. A pre- and post-test experiment was performed, with an eight-month training period in between, to evaluate whether or not the athletes' kicking technique and performance had been improved.
The results of the present study are described in two parts. The first part is the biomechanical analysis of Taekwondo kicking technique and performance. The analysis of technique and performance included kicking speed, kicking time duration, and muscle group recruitment. The second part is the development of a scientific training protocol. The design of the training protocol was based on the information obtained from the technique and performance evaluation in the pre-test. The protocol aimed to provide a specialised training technique for increasing muscle strength and reaction time during kicking.
Methodology Twelve subjects were recruited in Lok Wah Taekwondo Club. The Taekwondo practising history of the athletes was recorded in terms of length and frequency of training. General anthropometric parameters (height, weight), and physical fitness level of all subjects were measured (Table 1). Each subject gave informed consent and the study was explained to them before they participated in the experiment.
Table 1 Subjects Information Mean
SD
Age (year)
25.25
8.34
Weight (kg)
62.56
5.17
Height (cm)
170.78
6.42
Shoulder width (cm)
33.88
1.73
Years of training (year)
7.50
2.50
Frequency of training (hr/week)
2.67
1.87
Percentage of body fat (% fat)
11.28
4.29
Flexibility (cm)
40.13
5.97
Handgrip strength (kgf)
40.50
5.95
Note, The percentage of body fat was calculated by using the 7-skinfold sites with ACSM provided equation. Takei handgrip dynamometer was employed to measure the handgrip strength. ACUFLEX sit-and-reach box was employed in flexibility measurement.
In order to find out the prime muscles used in kicking, a pilot test was done before the beginning of the testing sessions. The results of the pilot test were then used to
investigate the activities of eight muscle groups. The muscle activity was expressed as a percentage of Maximum Voluntary Contraction (%MVC).
A pre- and post-test design was used in this project to examine the effectiveness of the training protocols. For each (pre- and post-) test session, the maximum voluntary isometric contraction test was conducted before the kicking trial started. Afterwards, each subject was asked to perform several kicking skills, including sidekick, pushing kick, slap kick and back kick. The performed skills were recorded by video filming and EMG measurement simultaneously. The recorded videotapes were then digitised on a motion analysis system.
The data collected from the pre-test were used as a baseline to design the training protocol, which focused on an exercise to strengthen the major muscles used during kicking and technique training.
The subjects were divided into two groups, training group and control group. After the pre-test, the training group underwent the training programme, whereas the control group was only asked to conduct the post-test without any special training.
Motion analysis.
Two Peak high-speed video cameras with 120 Hz in filming rate
and SOOHz in shutter speed were positioned at a distance of 5 metres from the subject to record the subject's movements (Figure 1). An 800W lamp was used to increase the light intensity during the filming. The recorded video tapes were then digitised and analysed on the 3-D module of the motion analysis system (BAS), To facilitate the transformation of image data from 2-D to 3-D, a 3-D calibration frame, two metres high, was used (Figure 3). A 21-point biomechanical model of an athlete's body was 7
used to perform the motion analysis. The output data from the motion analysis included time characteristics during kicking.
i:
Figure 1. The Peak high-speed video camera was placed at a distance of 5 metres from the subject.
Figure 2. The 800W lamp was used to increase the light intensity during the video filming.
Figure 3. A two-metre high frame was employed for 3-D motion analysis calibration.
EMG analysis.
The EMG activity of the muscles involved in kicking was
recorded with surface electrodes (silver / silver chloride, T-OO-S, Medicotest, 01stykke, Denmark) attached to the skin in a standardised manner: in the direction of the muscle fibres, with an inter-electrode distance of 3 cm. Before attaching the electrodes, the skin was shaved and rubbed with alcohol in order to lower the skin resistance. EMG electrodes were attached to several sites on the dominant leg (Figure 4).
The muscle groups included: •
Sartorius (Ch. 1)
•
Rectus femoris (Ch. 2)
•
Tensor fasciae latae (Ch. 4)
•
Vastus lateralis (Ch. 5)
•
Vastus medialis (Ch. 3)
•
Semitendinosus (hamstrings) (Ch. 6)
•
Biceps femoris (hamstrings) (Ch. 7)
•
Gastrocnemius (Ch. 8)
•
Shoulder (ground)
10
Figure 4. The EMG electrodes were placed on the selected muscles of the lower extremity.
After attaching the electrodes, the electrode cables were connected to the electrodes at one end and to the pre-amplifier at the other end. The pre-amplifier was close to the pads, eliminating the artifacts caused by subjects' movements. The pre-amplifier was fixed on the skin with paper, adhesive, tearable tape (3M, Transpore) to prevent any vibration of the amplifier.
11
In order to express the muscular activity of a muscle as the percentage of the MVC of that muscle, the measurement of EMG signals associated with the MVC EMG was conducted before the kicking trial began (Figure 5 and 6).
The MVC EMG was
employed in the later calculation of %MVC, which represented the muscular activities of the selected muscles.
Figure 5. The figure shows the test of isometric maximum voluntary contraction with knee flexion. re
Im
••!_.. * * y>
Figure 6. The figure shows the test of isometric maximum voluntary contraction with knee extension.
During the collection of EMG signals, the signals from the electrodes were preamplified, and transmitted through telemetric radio transmitters (915 Transmitter Unit, TELEMG, Italy). These signals were received by the receiving unit (920 Diversity Data Receiver, TELEMG, Italy), and passed through the optical fibre to the main unit. The main unit then amplified the signal by 1000 times. The quantitative analysis of the EMG signals was performed by an IBM-compatible computer. The raw EMG signals were low-pass (600 Hz) and high-pass (10 Hz) filtered and simultaneously A/D-converted (PCI-6071E, National Instruments, USA) at a sample rate of 2000 Hz for each channel. The rectification of EMG signal and 12
integration of EMG signal were calculated by data acquisition and analysis software (LabView, USA), with simultaneous visual control of the signals on the computer display.
Figure 7. The figure shows the connection box between the A/D converted card and signal from the instruments.
The information provided by EMG signal analysis included the degree of contraction of the selected muscles and the priority of muscle recruitment during kicking. This important information was then used in the design of the training protocol.
13
Kicking Test.
After conducting the MVC test, the subject was asked to perform
several sets of kicking in randomised order. The kicking style included the preparation form of kicking, kicking to the head level and kicking to the waist level in different styles of kicking (Table 2 and Figure 8, 9).
Table 2 The Kicking Stvle Preformed i n the Kicking Test Kicking style 1
Turning kick
2
Front turning kick
3
Reverse kick
4
One step side kick
5
Front side kick
6
Back kick
7
Pushing kick
8
Slap kick
Figure 8. The figure shows the standing preparation of kicking. The subject will use his back leg for kicking.
14
f!
Figure 9f The figure shows the pushing kick at the waist level. The number "1" means the first trial of this style of kicking and the letter "D" indicates the kicking sequence belongs to D series.
Training prQtocol
The design of the training protocol focused on two areas. The first
one was muscle strength. The results obtained from EMG analysis provided the information about the muscle activity during kicking. According to the degree of contraction, a muscle strengthening exercise was designed by using the Cybex NORM (isokinetic machine). The second focus was the techniques of kicking. The results obtained from motion analysis provided kinematics information on kicking. Such data were useful in improving the kicking technique and kicking effectiveness.
15
I*-*-'
Figure 10. The figure shows the condition of training with isokinetic concentric knee extension/flexion at 240 deg/s.
The training protocol was executed for a period of eight months. The experimental group added the new protocol to their usual training regime, while the control group kept to their usual training regime. The post-test session was arranged immediately after this period to examine the
16
Results Parti Biomechanical analysis of kicking Kicking analysis ANOVA was employed to examine the difference in the timing of kicks of different styles and heights. The results showed that there were significant differences in kicking time for different styles of kicking (p<.001) and different kicking heights (p<.001).
However, there were no
significant differences in kicking time between different preparation forms (Table 3). Table 4 shows the descriptive statistics of the kicking time for different preparation forms and styles. The graphical presentation of the kicking time for different preparation forms and styles is demonstrated in Figure 11.
One step
o
5
1—'—•
r
Kicking Styles with Standing Form before Kicking Figure 11, The graphical presentation of kicking time (±SD) for different kicking styles.
17
Table 3 *v>-junj ui ni-iv-f T j-f. 111 i».i»-i^jii5 j m»v *v* t
Height Levels and Preparation Forms Source
Type III
df
Mean
Sum of
F
Sig.
Square
Squares 0.133
14.665
0.000
136.743 15105.941
0.000
2.390
18
136.743
1
FORM
0.000
1
0.000
LEG_FORM
1.031
2
0.516
56.967
0.000
KICKING
0.249
5
0.050
5.493
0.000
KICK_LEV
0.350
1
0.350
38.710
0.000
FORM * LEG_FORM
0.007
2
0.004
0.404
0.668
FORM * KICKING
0.002
4
0.000
0.047
0.996
LEG_FORM * KICKING
0.000
0.
FORM * LEG_FORM * KICKING
0.000
0.
FORM * KICKJLEV
0.000
0.
LEG_FORM * KICK_LEV
0.002
2
FORM * LEG_FORM * KICK_LEV
0.000
0.
KICKING * KICKJLEV
0.000
1
FORM * KICKING * KICKJLEV
0.000
0.
LEG_FORM * KICKING * KICK_LEV
0.000
0.
FORM * LEG_FORM * KICKING *
0.000
0.
Corrected Model Intercept
0.005 0.941
. 0.001
0.117 0.890
0.000
0.004
0.953
.
KICKJLEV Error
1.892
209
Total
167.216
228
4.282
227
Corrected Total
0.009
Note. Df = degree of freedom; F = F value; FORM = the preparation form of kicking that consists of jumping and standing; LEGJFORM = the position of kicking leg before kicking that consists of front and back; KICKING = the styles of kicking that is shown in Table 2; KICKJLEV = the height level of kicking that consists of subject's head height and waist height.
18
Table 4
Kicking Styles
Height level
Mean (sec)
S.D.
N=12 Jumping Back leg Back kick
Low
0.870
0.065
Turning kick
Low
0.770
0.070
Pushing kick
Low
0.830
0.076
Slap kick
Low
0.780
0.084
Turning kick
Low
0.740
0.073
Side kick
Low
0.730
0.091
Low
0.960
0.114
Back kick
Low
0.890
0.074
Turning kick
Low
0.800
0.087
High
0.900
0.085
Pushing kick
Low
0.840
0.100
Slap kick
Low
0.790
0.076
Reverse kick
High
1.020
0.125
Low
0.720
0.099
High
0.850
0.107
Low
0.700
0.098
High
0.840
0.115
Low
0.960
0.116
High
1.090
0.119
Front leg
One step Side kick
Standing Back leg
Front leg Turning kick Side kick One step Side kick
19
The front turning kick to the waist level with standing preparation form was significantly faster (0.70 ± .098s) than the other styles of kicking. The one-step side kick to the head level with standing preparation form was significantly slower (1.09 ± .119s) than the other styles of kicking. Moreover, the use of the front leg was significantly faster than the use of the back leg for kicking (p<.001). The kicking time, when kicking to the subject's waist level, was significantly shorter than a kick to the subject's head level (p<.001). The kicking height showed significant effects on kicking time. The kicking time to a higher level was significantly longer than that to a low level (p<.001).
EMG analysis Table 5 shows the descriptive statistics of muscle activity in terms of %MVC for each selected muscle during kicking.
Table 5 Descriptive Statistics of Each Selected Muscle Activity (%IVIVC) During Kicking Mean (%MVC)
S. D.
N = 228
CHI
42.33
14.98
CH2
66.84
31.31
CHS
75.98
41.19
CH4
133.12
77.55
CHS
250.44
182.28
CH6
43.53
15.43
CH7
47.14
28.29
CHS
77.50
52.46
Note. CHI = Sartorius; CH2 = Rectus femoris; CHS = Vastus medialis; CH4 = Tensor fasciae latae; CHS = Vastus lateralis; CH6 = Semitendinosus; CH7 = Biceps femoris; CHS = Gastrocnemius.
ANOVA was employed to examine the difference in muscle activity during kicking (Table 6).
20
The statistical analysis showed that there was a significant difference in muscle activity among the selected muscles during kicking (p<.001).
The vastus lateralis and tensor fasciae latae showed significantly higher muscle activity during kicking when compared with other selected muscles. The muscle activity of the tensor fasciae latae was 133.12 ± 77.55%MVC and the muscle activity of the vastus lateralis was 250.44 ± 182.28%MVC during kicking.
The muscle activity of sartorius, rectus femoris and vastus medialis was 42.33 ± 14.98%MVC, 66.84 ± 31.31%MVC and 75.98 ± 41.19%MVC, respectively, during kicking.
Muscle activity of the hamstrings during kicking can be represented by the semitendinosus muscle and the biceps femoris, with the activity level of these muscles 43.53 ± 15.43%MVC and 47.14 ± 28.29%MVC, respectively.
Figure 12 is the graphical presentation of muscle activity among selected muscles during kicking. Note. Channel numbers are: 1 = Sartorius 2 = Rectus femoris 3 = Vastus medialis 4 = Tensor fasciae latae 5 = Vastus lateralis 6 = Semitendinosus
500; 450; 6* 400; 35q | £ soq | 250; "o cd 200; "o i5tr 1 ioq C/3
5(T
1
2
3
4
5
6
7
Channel number Figure 12. The graphical presentation of muscle activity %MVC (±SD) during kicking.
21
Table 6
Source
FACTOR1
Type III Sum
df
Mean Square
F
Sig.
of Squares FACTOR1
38164.95
1
38164.95
23.14
0.000
2377499.31
1
2377499.31
240.69
0.000
41730.89
1
41730.89
28.89
0.000
Order 4
2222649.56
1
2222649.56
267.33
0.000
Order 5
379819.04
1
379819.04
128.09
0.000
Order 6
1442389.26
1
1442389.26
237.22
0.000
Order 7
1414565.28
1
1414565.28
212.97
0.000
374399.21
227
1649.34
2242314.66
227
9878.04
327906.05
227
1444.52
Order 4
1887336.09
227
8314.26
Order 5
673115.69
227
2965.27
Order 6
1380244.64
227
6080.37
Order 7
1507788.46
227
6642.24
Linear Quadratic Cubic
Error(FACTORl) Linear Quadratic Cubic
Note. FACTOR1 represents the different activity level among different selected muscles during kicking.
Training programme According to the results of the analysis of kicking, relatively low muscle activity was found in the quadriceps and hamstrings. It is likely that the lower muscle activity of the quadriceps is due to the rapid movement of knee extension during kicking that, in turn, results in less muscle fibres being recruited. On the other hand, the quadriceps seems to be the prime mover in knee extension during kicking. According to this finding, we designed a training protocol that contains special training of knee extension and flexion under high-speed condition, in order to increase the muscle activity of the quadriceps during kicking.
The isokinetic training protocol contained knee concentric extension/flexion contraction at 240%, 20 repetitions in each set, 5 sets for each session, 3 sessions weekly.
22
Part II Training effect Table 7 shows the descriptive statistics of the isokinetic concentric contraction peak torque at 240 deg/s of knee extension before and after training for the control and training groups. The isokinetic concentric knee extension peak torque at 240 deg/s changed from 108.00 ± 14.93 Nm in the pre-test to 103.50 ± 11.43 Nm in the post-test for the control group. The isokinetic concentric knee extension peak torque at 240 deg/s showed significant increase, from 108.83 ± 16.95 Nm in the pre-test to 117.83 ± 18.99 Nm in the post-test for the training group.
Table 7 Descriptive Statistics of Isokinetic Concentric Contraction Peak Torque at 240 deg/s of Knee Extension Before and After Training for the Control and Training Groups GROUP
Mean (Nm)
S.D.
N=6 PRE
Control
108.00
14.93
Training
108.83
16.95
Control
103.50
11.43
Training
117.83
18.99
POST
Note, PRE = result from the pre-test; POST = result from the post-test; Nm = Newton meter. ANOVA was employed to examine the effect of the training programme on the isokinetic strength of knee extension at 240 deg/s. The results of the statistical analysis showed that there was a significant increase in the peak torque of the isokinetic concentric contraction at 240 deg/s at knee extension (p<.05).
23
Figure 13 shows the graphical presentation of isokinetic concentric contraction peak torque at 240 deg/s of knee extension before and after training for the control and training groups.
| |
| Control group | Training group
140-
ICU
o
120-
'i> I
10O Post-test
Pre-test
Figure 13. Graphical presentation of isokinetic concentric contraction peak torque at 240 deg/s of knee extension before and after training for the control and training groups. Table 8 shows the results of ANOVA in isokinetic concentric contraction peak torque at 240 deg/s of knee extension with significant change (p< .05).
Table 8 Extension Source
PREPOST
Type HI Sum df
Mean
of Squares
Square
F
Sig.
PREPOST
Linear
30.375
1
30.375
0.879
0.371
PREPOST * GROUP1
Linear
273.375
1
273.375
7.907
0.018
Error(PREPOST)
Linear
345.75
10
34.575
24
Discussion and Conclusion The results of this study were divided into two parts. The first part was the biomechanical analysis of Taekwondo kicking and the second part was the evaluation of the isokinetic training..
In the biomechanical analysis of Taekwondo kicking, the kicking time and the muscle activity were measured and ANOVA was employed to examine the difference among different kicking styles, The kicking time between different preparation forms showed no significant difference, indicating that, to perform a kick, different preparation movements will not result in different kicking times.
In the real Taekwondo competition, athletes always keep their body moving during the game. If the kicking time was the same for different preparation forms, then why do athletes move their body before attacking? Can they perform the same kicking performance with standing or jumping preparation form before kicking? It is common knowledge that in order to keep moving before kicking, the athletes spend a considerable amount of energy. If there was no any benefit from keeping the body moving before attacking, then the standing form would be a good choice, because it can save energy during the competition,
During kicking the muscle activity of the quadriceps was relatively low when comparing the tensor fasciae latae muscle with the vastus lateralis muscle. This phenomenon may be explained by the speed of the kicking motion. Since kicking involves a fast knee extension movement, the recruitment of the quadriceps muscle fibre may reduce. In such case, the ability to recruit muscle fibre under rapid movement becomes the most important factor affecting the exercise performance. To increase the exercise performance, the ability to recruit muscle fibre when moving rapidly should be enhanced. In order to enhance the ability to recruit muscle fibre during high speed contraction, a high speed isokinetic exercise programme was designed. The training protocol contained knee concentric extension/flexion at 240deg/s? 20 repetitions in each set, 5 sets for each session, 3 sessions weekly.
25
The constant preselected velocity during isokinetic movements allows the training to improve the muscular performance in dynamic conditions (Baltzopoulos and Brodie, 1989). Isokinetic training at a specific angular velocity increases the maximum torque of the muscle groups involved at that velocity (Lesmes et al. 1978). Numerous studies have also proved the training effects of isokinetic exercise (Baltzopoulos, 1989; Perrin, 1989; Perrin, 1993; Ewing, 1990; Johnson, 1976; Lesmes, 1978; Perrine, 1981 and Coyle, 1981). In our study, the speed of 240 deg/s was chosen as the training velocity. To increase the muscle strength under high angular velocity, isokinetic exercise training with a pre-selected speed for the dynamometer seems to be an effective way. In this study, the isokinetic concentric knee extension peak torque at 240deg/s was significantly increased after the isokinetic training at that angular velocity. The results show that, in order to increase the muscle strength in high-speed movement such as Taekwondo kicking, a relatively high angular velocity in isokinetic training should be selected.
In future, different training programmes could be designed for different muscle groups. The training exercise may contain isokinetic concentric, eccentric contraction, or isotonic contraction on specific muscle groups. Feedback from the subjects indicates that hip flexor and hip adductor seem to be important in Taekwondo kicking. Research work could focus on these muscle groups to see the possible changes in kicking performance. Moreover, information about the force applied to the kicking target is very useful for both researchers and coaches. Finally, a more reliable system should be developed to measure the actual force during the impact time.
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References Baltzopoulos, V, & Brodie, D. A. (1989). Isokinetic dynamometer: applications and limitations. Sports Medicine, 5(2), 101-116. Chan, K. M., & Maffulli, N. (Eds.). (1996). Principles and practice of isokinetics in sports medicine and rehabilitation: Williams & Wilkins. Cho, H. (1994). Analysis kicking. Australasian taekwondo, 3(3), 69-71. Cho, J. W., & Choe, M. A. (1988). A study on the effect of taekwondo training on the physical performance in preschool children- longitudinal studies. WTF taekwondo, 5(4), 3439.
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1 fl JAfi ,25,34
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HKP 796.815 H77 Hong, Youlian, 1946Biomechanical analysis of taekwondo kicking technique, performance & training effects Hong Kong : Research Dept,, Hong Kong Sports Development DateDue
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