Drop jump (DJ) is often used as a plyometric exercise to improve jumping performance. Training from improper drop heights and for improper durations lead to unfavorable biomechanical changes in the lower extremities when landing, which result in reduced training effects and even lower extremity injuries. Purpose. To study the effects of repeated DJ training at drop heights of 30 cm, 40 cm, and 50 cm (drop jump height (DJH) 30, DJH40, and DJH50) on lower extremity kinematics and kinetics. The 1st, 50th, 100th, 150th, and 200th DJs (DJ1, DJs50, DJs100, DJs150, and DJs200) were recorded by using a BTS motion capture system and force platform. The MATLAB software was used to compare the kinematic and stiffness data of DJ1, DJs50, DJs100, DJs150, and DJs200 with one-way ANOVA repeated measure. If there were significant differences, the LSD method was used for post hoc comparisons. Methods. Twenty healthy male Division III athlete volunteers were selected as subjects, and 200 drop jumps (DJs200) were performed from DJH30, DJH40, and DJH50. Results. The jumping height (JH), contact time (CT), and GRF increased with drop height, and the stiffness of the legs and ankle at DJH30 was higher than that at DJH40 and DJH50 (). Conclusion. Within DJs200, training at DJH50 yield the high impact easily leads to lower extremity injury; training at DJH30 can increase the stiffnesses of the legs and ankle joints, thus effectively utilizing the SSC benefits to store and release elastic energy, reducing the risk of lower extremity musculoskeletal injury. Therefore, coaches can choose different drop heights and training quantities for each person to better prevent lower extremity injury.

中文翻译：

---

不同的跌落高度训练对重复跌落跳跃过程中下肢运动学和刚度的影响

跳投（DJ）通常用作增强体力的锻炼。从不正确的跌落高度和不适当的持续时间进行训练会导致降落时下肢的生物力学发生不利变化，从而导致训练效果降低甚至下肢受伤。目的。研究重复的DJ训练在30 cm，40 cm和50 cm的跌落高度（跌落跳跃高度（DJH）30，DJH40和DJH50）对下肢运动学和动力学的影响。使用BTS运动捕获系统和测力平台记录了第1个，第50个，第100个，第150个和第200个DJ（DJ1，DJs50，DJs100，DJs150和DJs200）。使用MATLAB软件将DJ1，DJs50，DJs100，DJs150和DJs200的运动学和刚度数据与单向ANOVA重复测量进行比较。如果存在显着差异，则将LSD方法用于事后比较。方法。选择20名健康的男性III级运动员志愿者作为研究对象，并从DJH30，DJH40和DJH50进行了200次跳水（DJs200）。结果。跳高（JH），接触时间（CT）和GRF随着下落高度的增加而增加，DJH30的腿部和脚踝的刚度高于DJH40和DJH50的（）。 结论。在DJs200中，以DJH50进行训练可产生高冲击力，很容易导致下肢受伤；在DJH30进行的训练可以增加腿部和踝关节的刚度，从而有效地利用SSC的好处来存储和释放弹性能量，从而降低下肢肌肉骨骼损伤的风险。因此，教练可以为每个人选择不同的跌落高度和训练量，以更好地防止下肢受伤。