| Summary: | 博士 === 國立臺灣師範大學 === 體育學系 === 103 === Split step is a critical basis of badminton footwork. However, scientific studies on the timing and lower extremities kinetics of badminton split step remain insufficient. Therefore, the purpose of this study was to compare, for six direction movements, the players’ split timing, reaction time, and lower extremities kinetics during push-offs. Method：Eight collegiate elite male badminton players participated in this study (height: 173 ± 3.6 cm; weight: 68.1 ± 4.67 kg; age: 21 ± 3 years). Motion images were record by 10 Vicon MX-13+ (300 Hz) infrared cameras, Nexus 1.8 software for data collection, 2 force plates (Kistler 9287, AMTI 5507) to collect ground reaction forces, and Visual 3D software for calculating kinematic and kinetic data. The data obtained were assessed using the nonparametric Wilcoxon signed-rank test or Friedman’s 2-way analysis of variance by ranks in which the level of significance was set as α = .05. Result：There were no significant difference in the variables of COM, GRF and hop timing among six start direction before propulsion phase, and hop timing occurred in 14~37 ms after the opponent struck the shuttlecocks. During the propulsion phase, the leg which was opposite the movement direction have significantly greater lower extremity push-off force and total impulse than that in the homolateral leg. There were greater lower extremity stiffness and significantly greater horizontal push-off force of pushing leg in the midcourt start. In the left of front court start, there was greater peak horizontal push off force of pushing leg , but slower horizontal COM velocity. In the front court and midcourt, the energies generated by the hip and knee joints were significantly greater than that of the ankle joint in pushing leg ; in the rear court, the ankle joint showed significantly greater energy generation than the hip and knee joints did. The reaction time of each start direction occurred about 0.3 sec after the players struck the shuttlecocks. The total reaction time of midcourt was faster than the front court and rear court. Conclusion : The prepare movement before the propulsion phase must be consistent and hop simultaneously with the opponent struck the shuttlecocks. The leg opposite the movement direction was the main pushing leg. Greater lower extremity stiffness, horizontal push-off force and shorter total reaction time were needed in midcourt start. In the left of front court, it needed greater horizontal push off force to start. The main pushing joint of lower extremity was hip and knee in the front court and the midcourt start, but the main pushing joint in the rear court was ankle. When lower extremity have correct pushing direction and peak pushing off force within 0.3 sec, the players will have a better hit back in badminton competition.
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