模拟高空跳伞着陆状态下踝关节动态角速度与垂直反作用力的测定

 目的 通过模拟高空跳伞着陆训练环境测定不同高度半蹲式跳伞着陆状态下的踝关节角速度、地面垂直反作用力，为预防跳伞着陆踝部损伤提供生物力学依据。方法 募集18名健康志愿者，包括空军地勤人员9名、职业跳伞人员9名。两组受试者身高、体重的差异无统计学意义。受试者分别从30 cm和60 cm高的跳台以半蹲式跳伞着陆并腿姿势跳落到测力台上。高速摄像机记录着陆过程，测定踝关节跖屈角位移及时间、地面垂直反作用力，计算角速度，分析踝关节动态角位移、角速度、垂直作用力与不同高度的相关性。结果 30 cm高度：地勤人员组与跳伞运动员组踝关节角位移分别为25.73°±8.13°、20.05°±12.27°，垂直反作用力分别为（3 372.4±748.6） N、（5 181.5±1 726.2） N，受力时间分别为（0.049±0.015） s、（0.012±0.004） s，缓冲时间分别为（1.397±0.746） s、（1.737±0.451） s，差异均有统计学意义。60 cm高度：地勤人员组与跳伞运动员组踝关节角速度分别为（25.45±15.01） °/s、（16.51±4.18） °/s，垂直反作用力分别为（4 616.0±1124.7） N、（7 119.5±2 307.4） N，受力时间分别为（0.048±0.013） s、（0.015±0.006） s，缓冲时间分别为（0.922±0.347） s、（1.617±0.547） s，差异均有统计学意义。结论 从不同的测试高度跳下，跳伞运动员组的地面垂直反作用力大于地勤人员组，但角速度及角位移小于地勤人员组。对比地勤人员组，跳伞运动员组的受力时间短而缓冲时间更长。

Measurement of the angular velocity and perpendicular ground reaction force of the ankle joint in parachute landing simulation

Objective To measure the angular velocity and perpendicular ground reaction force of the ankle joint under different heights with half-squat jumping in parachute training simulation, providing a reliable experiment basis for the preventing of ankle injury. Methods A total of 18 volunteers participated in this study. The experimental group included 9 male with experience of parachute landing, while the other 9 male without experience of parachute landing were assigned to the control group. Each subject was instructed to jump off a platform with a height of 30 cm and 60 cm and land on a hard surface in a half-squat posture. The dynamic landing process was recorded with a high speed camera and the biomechanical data was collected and analyzed, including perpendicular ground reaction force, angular displacement, velocity and acting time. Results From 30 cm's height, the ankle angular displacement of the control group was significantly larger than the experimental group (25.73°±8.13° vs 20.05°±12.27°, P＜0.05）. The perpendicular ground reaction force of the control group was significantly smaller than the experimental group (3 372.4±748.6 N vs 5 181.5±1 726.2 N, P＜0.05). The acting time of the control group was significantly longer than the experimental group (0.049±0.015 s vs 0.012±0.004 s, P＜0.05). The buffer time of the control group was significantly shorter than the experimental group (1.397±0.746 s vs 1.737±0.451 s, P＜0.05). From 60 cm's height, the ankle angular velocity of the control group was significantly higher than the experimental group (25.45±15.01 °/s vs 16.51±4.18 °/s, P＜0.05）. The perpendicular ground reaction force of the control group was significantly smaller than the experimental group (4 616.0±1 124.7 N vs 7 119.5±2 307.4 N, P＜0.05). The acting time of the control group was significantly longer than the experimental group (0.048±0.013 s vs 0.015±0.006 s, P＜0.05). The buffer time of the control group was significantly shorter than the experimental group (0.922±0.347 s vs 1.617±0.547 s, P＜0.05). Conclusion Jumping from different heights, the experimental group was larger in perpendicular ground reaction force but smaller in the angular velocity and displacement than the control group. There was a shorter acting time and a longer buffer time in the experimental group than the control group.