van Dieën Jaap H, Spanjaard Marcel, Könemann Reinier, Bron Lennart, Pijnappels Mirjam
Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, NL-1081 BT Amsterdam, The Netherlands.
J Biomech. 2008 Aug 7;41(11):2417-21. doi: 10.1016/j.jbiomech.2008.05.022. Epub 2008 Jul 10.
When stepping down from a height difference in ongoing gait, subjects are known to use a heel landing at small height differences and switch to toe landing for larger height differences. We hypothesized that in toe landing, the leading leg can perform more negative work, to control the momentum gained during the descent, than in heel landing. Ten young male participants walked over a 10-m walkway at 5km/h to step down a height difference of 10cm halfway, using a heel or toe landing in five trials each. Kinematic data and ground reaction forces under the leading and trailing legs were recorded. Inverse dynamical analysis of both strategies showed that the leading leg performed more negative work in toe landing, while the vertical velocity at ground contact was lower. In addition, the impact forces were lower in toe landing than in heel landing. Toe landing was found to reduce gait velocity in the first step on the lower level and required higher moments and negative power around the ankle joint than heel landing. Our results indicate that heel landing may be preferred when stepping down small height differences, because it is less demanding especially for the plantar flexor muscles, while toe landing may be preferred for stepping down larger height differences, because it improves control over the momentum gained during the descent.
在持续行走过程中从一定高度差向下迈步时，已知受试者在高度差较小时会采用脚跟先着地的方式，而在高度差较大时则会切换为脚尖先着地。我们推测，在脚尖先着地时，领先腿比脚跟先着地时能够做更多的负功，以控制下降过程中获得的动量。10名年轻男性参与者以5公里/小时的速度在10米长的通道上行走，中途要下降10厘米的高度差，每种方式各进行5次试验，分别采用脚跟先着地或脚尖先着地。记录领先腿和跟随腿下方的运动学数据和地面反作用力。对两种策略的逆动力学分析表明，脚尖先着地时领先腿做的负功更多，而着地瞬间的垂直速度更低。此外，脚尖先着地时的冲击力比脚跟先着地时更低。研究发现，脚尖先着地会降低较低平面第一步的步速，并且与脚跟先着地相比，需要在踝关节周围产生更高的力矩和负功率。我们的结果表明，在下降较小高度差时，脚跟先着地可能更受青睐，因为它的要求较低，尤其是对跖屈肌而言；而在下降较大高度差时，脚尖先着地可能更受青睐，因为它能更好地控制下降过程中获得的动量。
