Kramer Patricia Ann, Sarton-Miller Isabelle
Department of Anthropology, University of Washington, Seattle, WA 98195-3100, USA.
Gait Posture. 2008 Feb;27(2):209-15. doi: 10.1016/j.gaitpost.2007.03.009. Epub 2007 Apr 24.
Velocity and body mass have well-known influences on the amount of metabolic energy that animals require to walk. This relationship could stem from the fact that both are key variables in calculating the mechanical energy of a system in motion. Other variables, like leg length, are also important in mechanical energy calculations and two mechanical formulations that incorporate leg length, Froude number (Fr) and the LiMb model, have been shown to correlate with human metabolic energy expenditure. Both, however, include velocity as a key variable in their calculations, so we wondered if the correlation might derive solely from their relationship with velocity rather than leg length. Using the energetic data and gait parameters from 24 human adults and 48 children, we tested several variables - velocity (V), V(2), body mass, leg length, Fr and LiMb - to see which combinations best explained the variation in oxygen consumption, a proxy of metabolic energy expenditure. An equation with V(2), body mass and leg length as covariates produced the highest R(2), explaining 88% of the variation when all subjects were combined. No significant differences in the predictive power of velocity, V(2), Fr or LiMb were detected, prompting us to conclude that neither Fr nor LiMb compensate for the effect of leg length. Leg length does influence the energetic expenditure of walking humans, but Fr and LiMb do not appear to adequately reflect that effect. The development of another method to compensate for the effect of leg length on metabolic energy consumption is essential.
速度和体重对动物行走所需的代谢能量有众所周知的影响。这种关系可能源于这样一个事实，即两者都是计算运动系统机械能的关键变量。其他变量，如腿长，在机械能计算中也很重要，并且已经证明两种纳入腿长的力学公式，即弗劳德数（Fr）和肢体模型（LiMb），与人类代谢能量消耗相关。然而，两者都将速度作为其计算中的关键变量，所以我们想知道这种相关性是否可能仅仅源于它们与速度的关系，而非腿长。利用24名成年人和48名儿童的能量数据和步态参数，我们测试了几个变量——速度（V）、V²、体重、腿长、弗劳德数和肢体模型——以确定哪些组合能最好地解释作为代谢能量消耗指标的氧气消耗的变化。一个以V²、体重和腿长作为协变量的方程产生了最高的R²，当所有受试者合并时，解释了88%的变化。在速度、V²、弗劳德数或肢体模型的预测能力方面未检测到显著差异，这促使我们得出结论，弗劳德数和肢体模型都不能补偿腿长的影响。腿长确实会影响人类行走的能量消耗，但弗劳德数和肢体模型似乎没有充分反映这种影响。开发另一种方法来补偿腿长对代谢能量消耗的影响至关重要。
