Mechanics and energetics of swinging the human leg
Mechanics and energetics of swinging the human leg
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DOI：
10.1242/jeb.01408
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发表时间：
2005-02-01
影响因子：
2.8
通讯作者：
Kuo, AD
中科院分区：
文献类型：
--
作者：
Doke, J;Donelan, JM;Kuo, AD
我们测量了摆动一条腿需要消耗多少代谢能量。先前的步行动力学模型预测，步行的代谢成本增加与步长和步频相互权衡，以确定在给定速度下的最佳步组合。单摆动力学表明，以高步频行走的成本可能与驱动腿相对于身体来回运动有关，速度大约随频率的四次方增加，这可能是由于短时间内产生肌肉力量的经济性较低。对于腿以比其自然频率更快的速度进行孤立摆动，预计会有类似的成本。我们构建了一个装置来测量腿部所做的功，并测量了人类受试者（N=12）以0.5-1.1 Hz的频率和固定幅度摆动一条腿时的代谢成本。在这些频率下，机械功的速率范围为0.02-0.27 W kg（-1）。摆动腿的净代谢率（减去安静站立的净代谢率）从0.41-2.10 W kg（-1）增加，大约与频率的四次方（R-2=0.92）成比例，并与短时间内产生力量的假设成本成比例。生产力和工作的成本可以解释这种增加。粗略比较，以0.9 Hz的典型步频来回移动双腿，可能消耗大约1/3的净能量（2.8+/-0.8 W kg（-1）），需要步行1.3 m s（-1）。
We measured how much metabolic energy is expended to swing a human leg. A previous dynamical model of walking predicted that increasing metabolic costs for walking with step length and step frequency trade-off against each other to determine the optimum step combination at a given speed. Simple pendulum dynamics indicate that the cost of walking at high step frequencies could be associated with driving the legs back and forth relative to the body, at a rate increasing approximately with the fourth power of frequency, possibly due to the low economy of producing muscle force for short durations. A similar cost would be expected for isolated swinging of a leg at faster than its natural frequency. We constructed an apparatus to measure work performed on the leg, and measured metabolic cost as human subjects (N=12) swung one leg at frequencies 0.5-1.1 Hz and fixed amplitude. Rate of mechanical work ranged from 0.02-0.27 W kg(-1) over these frequencies. Net metabolic rate for leg swinging (subtracting that for quiet standing) increased from 0.41-2.10 W kg(-1), approximately with the fourth power of frequency (R-2=0.92) and in proportion to a hypothesized cost of force production for short durations. The costs of producing force and work could account for the increase. In a crude comparison, moving the legs back and forth at a typical stride frequency of 0.9 Hz, might consume about one-third of the net energy (2.8+/-0.8 W kg(-1)) needed for walking at 1.3 m s(-1).