McNitt-Gray J L
Department of Exercise Sciences, University of Southern California, Los Angeles 90089-0652.
J Biomech. 1993 Sep;26(9):1037-46. doi: 10.1016/s0021-9290(05)80003-x.
In this study, the landing preferences of gymnasts (n = 6) and recreational athletes (n = 6) were determined by comparing the changes in lower extremity kinetics of drop landings performed from three heights (0.32-1.28 m). Net joint moments and work done on the extensor muscles of the ankle, knee, and hip were selected as variables representative of the demand placed on the muscles responsible for controlling flexion and dissipating the load. Kinematic and kinetic two-dimensional data were acquired simultaneously using high-speed film (202.4 fps) and a force plate (1000 Hz). Reaction forces and lower extremity joint motions were used to calculate net joint forces, net joint moments powers, and work done on the extensor muscles of the ankle, knee, and hip. Results indicated that the extensor joint moments tended to peak earlier after contact with increases in velocity, but the temporal sequence of events was maintained independently of velocity or group. As impact velocity increased, net peak extensor moments and work done on the extensor muscles significantly increased. Significantly larger ankle and hip peak extensor moments were observed for the gymnasts across velocities as compared to the recreational athletes. No significant differences in work done on the extensor muscles were noted between groups. Significant interaction effects indicate that gymnasts chose to dissipate the loads at contact by using larger ankle and hip extensor moments at higher impact velocities than the recreational athletes, whereas recreational athletes chose to adjust their strategy by using greater degrees of hip flexion (McNitt-Gray, Int. J. Sport Biomech, 7, 201-204, 1991) and longer landing phase durations than the gymnasts. The greater demands placed on the ankle and hip extensors by the gymnasts, as compared to the recreational athletes, may be explained by the need to maintain balance during competitive gymnastics landings or, perhaps, by the inability of recreational athletes to produce larger extensor moments at the ankle or hip during landings from great heights.
在本研究中，通过比较从三个高度（0.32 - 1.28米）进行的下落着地时下肢动力学的变化，确定了体操运动员（n = 6）和业余运动员（n = 6）的着地偏好。选择踝关节、膝关节和髋关节伸肌上的净关节力矩以及所做的功作为代表负责控制屈曲和消散负荷的肌肉所承受需求的变量。使用高速摄像机（202.4帧/秒）和测力台（1000赫兹）同时采集运动学和动力学二维数据。利用反作用力和下肢关节运动来计算净关节力、净关节力矩功率以及踝关节、膝关节和髋关节伸肌上所做的功。结果表明，随着速度增加，着地后伸肌关节力矩倾向于更早达到峰值，但事件的时间顺序不受速度或组别影响而保持不变。随着撞击速度增加，伸肌净峰值力矩和伸肌上所做的功显著增加。与业余运动员相比，体操运动员在各个速度下踝关节和髋关节的伸肌峰值力矩都显著更大。两组之间在伸肌上所做的功没有显著差异。显著的交互作用表明，与业余运动员相比，体操运动员选择在更高撞击速度下通过使用更大的踝关节和髋关节伸肌力矩来在着地时消散负荷，而业余运动员选择通过比体操运动员更大程度的髋关节屈曲（McNitt - Gray，《国际运动生物力学杂志》，7，201 - 204，1991）和更长的着地阶段持续时间来调整他们的策略。与业余运动员相比，体操运动员对踝关节和髋关节伸肌的更大需求，可能是由于在竞技体操着地过程中保持平衡的需要，或者也许是由于业余运动员在从高处着地时无法在踝关节或髋关节产生更大的伸肌力矩。
