Moritz Chet T, Farley Claire T
Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA.
Proc Biol Sci. 2003 Aug 22;270(1525):1741-6. doi: 10.1098/rspb.2003.2435.
Fast-moving legged animals bounce along the ground with spring-like legs and agilely traverse variable terrain. Previous research has shown that hopping and running humans maintain the same bouncing movement of the body's centre of mass on a range of elastic surfaces by adjusting their spring-like legs to exactly offset changes in surface stiffness. This study investigated human hopping on damped surfaces that dissipated up to 72% of the hopper's mechanical energy. On these surfaces, the legs did not act like pure springs. Leg muscles performed up to 24-fold more net work to replace the energy lost by the damped surface. However, considering the leg and surface together, the combination appeared to behave like a constant stiffness spring on all damped surfaces. By conserving the mechanics of the leg-surface combination regardless of surface damping, hoppers also conserved centre-of-mass motions. Thus, the normal bouncing movements of the centre of mass in hopping are not always a direct result of spring-like leg behaviour. Conserving the trajectory of the centre of mass by maintaining spring-like mechanics of the leg-surface combination may be an important control strategy for fast-legged locomotion on variable terrain.
行动迅速的有腿动物依靠如弹簧般的腿部在地面上跳跃前进，并能灵活穿越各种地形。先前的研究表明，跳跃和奔跑的人类通过调整如弹簧般的腿部，精确抵消表面刚度的变化，从而在一系列弹性表面上保持身体重心相同的弹跳运动。本研究调查了人类在能耗散高达跳跃者机械能72%的阻尼表面上的跳跃情况。在这些表面上，腿部的表现并不像纯弹簧。腿部肌肉所做的净功最多可达24倍，以补充被阻尼表面耗散的能量。然而，将腿部和表面综合考虑，在所有阻尼表面上，这种组合似乎表现得像一个刚度恒定的弹簧。通过不管表面阻尼如何都保持腿部与表面组合的力学特性，跳跃者也能保持重心运动。因此，跳跃时重心的正常弹跳运动并不总是如弹簧般腿部行为的直接结果。通过保持腿部与表面组合的弹簧般力学特性来维持重心轨迹，可能是在多变地形上快速腿部运动的一种重要控制策略。
