Optimal walking speed following changes in limb geometry
Optimal walking speed following changes in limb geometry
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DOI：
10.1242/jeb.054452
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发表时间：
2011-07-01
影响因子：
2.8
通讯作者：
Cheron, Guy A.
中科院分区：
文献类型：
--
作者：
Leurs, Francoise;Ivanenko, Yuri P.;Cheron, Guy A.
动态相似原理指出，当速度归一化为无因次弗劳德数(Fr)时，几何相似动物的最佳行走速度与大小无关。此外，各种研究已经表明，肢体几何形状完全不同的动物的无量纲最佳速度(Fr类似于0.25)相似。在这里，我们想知道人类的最佳行走速度是否仅取决于肢体总长度，或者肢体节段比例是否起着关键作用。如果最佳行走速度仅仅取决于四肢的长度，那么，当受试者踩着高跷行走时，他们以更快的最佳速度行走时应该比没有踩着高跷行走时消耗更少的新陈代谢能量。为了验证这一预测，我们比较了成年人在跑步机上以不同的速度行走时的运动学、肌电活动和氧气消耗，这些人戴着和不戴着人工延长小腿40厘米的关节高跟鞋。踩高跷涉及运动学和肌电模式的非线性重组。特别是，我们发现在摆动阶段，近端屈伸肌的交替活动显著增加，尽管归一化步长显著缩短。每单位距离的最小代谢成本出现在大致相同的绝对速度，对应较低的Fr数(Fr类似于0.17)比正常步行(Fr类似于0.25)。这些发现与肢体几何优化和运动学协调策略在最小化人类行走能量消耗方面的重要作用是一致的。
The principle of dynamic similarity states that the optimal walking speeds of geometrically similar animals are independent of size when speed is normalized to the dimensionless Froude number (Fr). Furthermore, various studies have shown similar dimensionless optimal speed (Fr similar to 0.25) for animals with quite different limb geometries. Here, we wondered whether the optimal walking speed of humans depends solely on total limb length or whether limb segment proportions play an essential role. If optimal walking speed solely depends on the limb length then, when subjects walk on stilts, they should consume less metabolic energy at a faster optimal speed than when they walk without stilts. To test this prediction, we compared kinematics, electromyographic activity and oxygen consumption in adults walking on a treadmill at different speeds with and without articulated stilts that artificially elongated the shank segment by 40 cm. Walking on stilts involved a non-linear reorganization of kinematic and electromyography patterns. In particular, we found a significant increase in the alternating activity of proximal flexors-extensors during the swing phase, despite significantly shorter normalized stride lengths. The minimal metabolic cost per unit distance walked with stilts occurred at roughly the same absolute speed, corresponding to a lower Fr number (Fr similar to 0.17) than in normal walking (Fr similar to 0.25). These findings are consistent with an important role of limb geometry optimization and kinematic coordination strategies in minimizing the energy expenditure of human walking.