Taekwondo

ISBS 2005 / Beijing, China

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THE BIOMECHANICAL ANALYSIS OF THE TAEKWONDO FRONT-LEG AXE-KICK
Yeh.Jung Tsai1, Guo-Hong Gu 2, Chia.Jung Lee 2, Chen-Fu Huang 2 and Chien-Lu Tsai 2
'National Taipei Teachers College, Taipei, Chinese Taipei
2National Taiwan Normal University, Taipei, Chinese Taipei

The purpose of the study was to analyze the biomechanics of taekwondo front-leg axe­kick. One force plates, two synchronized high-speed cameras were used to measure biomechanical parameters in each phase of the front-leg axe-kick. The results included: 1. The average reaction time and movement time were 0.423 sand 0.327 s, which respectively occupied about 56% and 44% of attack time. 2. The maximum velocity of hip, knee and ankle were 1.74 m/s, 5.25 m/s and 7.43 m/s respectively.When the kicking leg touched the target, the velocity of knee and ankle were 0.78m/s, 1.72m1s, and 4.64m1s respectively. 3. The peak vertical GRF and impulse were 0.96 SW and 77.57N-s. For decreasing the movement time, it's suggested that an athlete should increase the power and flexibility of lower extremities during the training section. KEY WORDS: taekwondo, axe-kick, biomechanic

INTRODUCTION:Taekwondo is a competitive sport in martial arts. The kicking leg, the unique feature to Taekwondo, is the major attack weapon in Ihe competition (Hon, 1997). Previous studies (Kim, 1'988; Chein, 1991; Tsai, 1998) showed that axe-kick was one of the main offensive actions with high percentage of offense, scoring and success during competition. Axe-kick is the main method of face kick, and whichcan be divided into front-leg axe-kick and back-leg axe-kick. The purpose of the kick is to attack opponent's head and genetrate a powerful and downward force. Recently study (Chen, Chin & Shiang, 2004) showed that front-leg axe-kick was the critical attack action for the percentage of success during competition. Generally, the faster and the more powerful the front-leg axe-kick is the moreadvantages can be gained. However, there was little study to discuss the biomechanics about front-leg axe-kick. The purpose of this study was to analyze the attack time and ground reaction force (GRF) of kicking leg of front-leg axe-kick. METHODS: Eight skilled college male Taekwondo athletes (mean age, weight, height and trained experience were 21.12 ± 2.13 years, 66.75 ± 6.52 kg, 173.63 ± 3.74 cm and11.38 ± 2.62 years respectively) served as subjects for this study. A:II subjects were standing on a force plate (AMTII, 1250 Hz) by their front leg, and then to kick the target after the signal of light appeared. Two high-speed cameras (Redlake, 125 Hz) were used to determine the three-dimensional kinematics data during action. The reaction time (RT) and movement time (MT) were collected by Bio-pacSystems which was used to synchronize the trigger of force plate and the signal of light. The attack time (AT) was defined as the summation of RT and MT. The motion of front-leg axe-kick (Figure 1) was divided into leg-lifting phrase (from the moment of leg taking off till the moment of minimum joint angles of knee) and leg-downing phrase. The impulse was integrated from the appearing of signalof light to taking off of leg.

Figure 1 The free body diagram of Taekwondo front-leg. axe-kick.

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ISBS 2005 / Beijing, China

Table 1 The variables of reaction time, motion time and attack time. Variables (N=8) RT (s) MT (s) AT (s) Mean 0.423 0.327 0.750 S.o. 0.049 0.026 0.069 Ratio 0.5& 0.44 1.00

The attack time consisted of reaction time and movement time. Table 1 indicated thatthe averaged time of reaction time (RT) and movement time (MT) were 0.423 ± 0.049 sand 0.327 ± 0.026 s, which were about 44% and 56% of attack time (AT). Based on previous study (Tsai, 1999), the RT, MT and AT of back-leg axe-kick were 0.531 s, 0.355 sand 0.886 s, respectively. The reason that the back leg was used to support body during front-leg axe­ kick. Therefore, it was benefit to reduce...