Kram R, Domingo A, Ferris D P
Human Biodynamics Department, University of California, Berkeley 94720-4480, USA.
J Exp Biol. 1997 Feb;200(Pt 4):821-6. doi: 10.1242/jeb.200.4.821.
We investigated the effect of reduced gravity on the human walk-run gait transition speed and interpreted the results using an inverted-pendulum mechanical model. We simulated reduced gravity using an apparatus that applied a nearly constant upward force at the center of mass, and the subjects walked and ran on a motorized treadmill. In the inverted pendulum model for walking, gravity provides the centripetal force needed to keep the pendulum in contact with the ground. The ratio of the centripetal and gravitational forces (mv2/L)/(mg) reduces to the dimensionless Froude number (v2/gL). Applying this model to a walking human, m is body mass, v is forward velocity, L is leg length and g is gravity. In normal gravity, humans and other bipeds with different leg lengths all choose to switch from a walk to a run at different absolute speeds but at approximately the same Froude number (0.5). We found that, at lower levels of gravity, the walk-run transition occurred at progressively slower absolute speeds but at approximately the same Froude number. This supports the hypothesis that the walk-run transition is triggered by the dynamics of an inverted-pendulum system.
我们研究了失重对人类步行-跑步步态转换速度的影响，并使用倒立摆力学模型对结果进行了解释。我们使用一种在质心处施加近乎恒定向上力的装置模拟失重，受试者在电动跑步机上行走和跑步。在步行的倒立摆模型中，重力提供了使摆锤与地面保持接触所需的向心力。向心力与重力的比值((mv^2/L)/(mg))简化为无量纲的弗劳德数((v^2/gL))。将此模型应用于行走的人类，(m)是体重，(v)是前进速度，(L)是腿长，(g)是重力。在正常重力下，人类和其他具有不同腿长的两足动物都选择在不同的绝对速度下从步行转换为跑步，但弗劳德数大致相同（0.5）。我们发现，在较低重力水平下，步行-跑步转换发生的绝对速度逐渐变慢，但弗劳德数大致相同。这支持了步行-跑步转换是由倒立摆系统的动力学触发的这一假设。
