Mechanical work for step-to-step transitions is a major determinant of the metabolic cost of human walking.
Mechanical work for step-to-step transitions is a major determinant of the metabolic cost of human walking.
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发表时间：
2002-12
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通讯作者：
J. Donelan;R. Kram;A. Kuo
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作者：
J. Donelan;R. Kram;A. Kuo
在步行的单站姿阶段，质心运动类似于倒立摆。理论上，产生摆动运动不需要机械功，但是在步骤之间的过渡期间，需要功来将质心速度从一个摆动弧重定向到下一个摆动弧。碰撞模型预测负功的速率与步长的四次方成正比。需要正功来恢复损失的能量，这可能会要求一定比例的代谢成本。我们测试了这些预测与人类（N=9）步行的步长范围（0.4-1.1米），同时保持步频固定在1.8赫兹。我们使用测力板测量个体肢体的外部机械功，使用间接量热法测量代谢率。正如预测的那样，平均负和正的外部机械功率随着步长的四次方而增加（从1 W到38 W; r（2）=0.96）。代谢率随步长的4次方（从7 W到379 W，r（2）=0.95）而增加，与机械功率呈线性关系。一步一步过渡的机械功，而不是摆动运动本身，似乎是步行代谢成本的主要决定因素。
In the single stance phase of walking, center of mass motion resembles that of an inverted pendulum. Theoretically, mechanical work is not necessary for producing the pendular motion, but work is needed to redirect the center of mass velocity from one pendular arc to the next during the transition between steps. A collision model predicts a rate of negative work proportional to the fourth power of step length. Positive work is required to restore the energy lost, potentially exacting a proportional metabolic cost. We tested these predictions with humans (N=9) walking over a range of step lengths (0.4-1.1 m) while keeping step frequency fixed at 1.8 Hz. We measured individual limb external mechanical work using force plates, and metabolic rate using indirect calorimetry. As predicted, average negative and positive external mechanical work rates increased with the fourth power of step length (from 1 W to 38 W; r(2)=0.96). Metabolic rate also increased with the fourth power of step length (from 7 W to 379 W; r(2)=0.95), and linearly with mechanical work rate. Mechanical work for step-to-step transitions, rather than pendular motion itself, appears to be a major determinant of the metabolic cost of walking.