Biomechanical Analyses of Jumping-Back Kick of two Preparatory Standing Postures in Taekwondo

[[abstract]]Taekwondo is a national sport in Taiwan which can win medals in Asian Games and Olympic Games. Jumping-back kick is used in competition to counterattack round-kick. The purpose of this study was to describe the movement characteristics of jumping-back kick at different height from two preparatory standing postures (jump and squat) in order to provide information for teaching and training of jumping-back kick. The participants included 10 elite Taekwondo athletes whose mean age, height, and weight were 19.7±0.8 yrs, 178.6±3.5 cm, and 66.0±6.4 kg respectively. The kinematics and kinetics data of jumping-back kick were collected simultaneously by two AMTI force plate (1000Hz), ten motion system cameras (200Hz), and Bio-Pac MP35 pressure measuring system. The angular kinematics and kinetics data were calculated by program written in Matlab 7.01 software. Nonparametric statistic test was used to test the difference of parameters among two preparatory standing postures and two kicking heights （jump preparatory standing posture-middle height kicking [JK1], jump preparatory standing posture -top height kicking [JK2], squat preparatory standing posture- middle height kicking [SK1], squat preparatory standing posture-top height kicking [SK2]）. Pearson product-moment correlation was conducted to determine the relations of each parameter of kinematics and kinetics to kicking performance. The results were showed as below: 1. JK2 had faster movement speed than did SK2. There was no difference between JK1 SK1 and regarding movement speed. 2. JK2 had greater impulse force than did SK2. There was no difference between JK1 and SK1 in impulse force. 3. Regarding the angular velocity of trunk, the maximum angular velocities of shoulder axes at JK2 was greater than that at SK2. Besides, the maximum angular velocity of shoulder axis at JK1 was greater than that at SK1. 4. JK1’s and JK2’s offensive foot have the greater peak vertical ground reaction force (GRF) and peak anterior-posterior force and impulse than were SK1’s and SK2’s offensive foot. Conclusion: In terms of the results, jump preparatory standing posture will facilitate the better kicking performance when perform jumping-back kick at top height target. Therefore, jump preparatory standing posture is recommended for taekwondo athletes and coaches in skills training for kicking at top height targets.