Mechanics and energetics of load carriage during human walking
Mechanics and energetics of load carriage during human walking
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DOI：
10.1242/jeb.091587
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发表时间：
2014-02-01
影响因子：
2.8
通讯作者：
Kuo, Arthur D.
中科院分区：
文献类型：
--
作者：
Huang, Tzu-wei P.;Kuo, Arthur D.
虽然人类显然会消耗更多的能量来行走额外的负荷，但目前还不清楚是什么生物力学机制导致了这种增加。一个可能的贡献是在身体质心（COM）上执行的机械功，简单的模型预测应该随着增加的质量线性增加。这项工作应该主要由下肢关节完成，尽管分布不明，并消耗一定比例的代谢能量。因此，我们测试了正常成人（N=8）以恒定速度（1.25 m s（-1））步行，不同的背包负荷高达体重的40%。我们测量了机械功（在COM上进行的功和来自逆动力学的联合功），以及通过呼吸测定法测量的代谢能量消耗。发现两种测量的工作都随着负载的增加而近似线性地增加，对于每1 kg的额外负载，COM工作速率增加约1.40 W。关节都做了功，但正功增加最多的是蹬地时的踝关节（占步幅的45-60%）和碰撞后反弹时的膝关节（占步幅的12-30%）。髋关节在接近站姿结束时做的负功越来越多。代谢能量消耗率也随负荷近似线性增加，每增加1 kg负荷约增加7.6 W。功和代谢成本增加的比率产生了约16%的相对恒定的效率。代谢成本没有解释的工作似乎是相对恒定的负荷，并没有表现出特定的趋势。大部分增加的负重成本似乎可以用正的机械功来解释，特别是关于脚踝和膝盖，功和代谢成本都随着增加的质量几乎线性增加。
Although humans clearly expend more energy to walk with an extra load, it is unclear what biomechanical mechanisms contribute to that increase. One possible contribution is the mechanical work performed on the body center of mass (COM), which simple models predict should increase linearly with added mass. The work should be performed primarily by the lower extremity joints, although in unknown distribution, and cost a proportionate amount of metabolic energy. We therefore tested normal adults (N=8) walking at constant speed (1.25 m s(-1)) with varying backpack loads up to 40% of body weight. We measured mechanical work (both performed on the COM and joint work from inverse dynamics), as well as metabolic energy expenditure through respirometry. Both measures of work were found to increase approximately linearly with carried load, with COM work rate increasing by approximately 1.40 W for each 1 kg of additional load. The joints all contributed work, but the greatest increase in positive work was attributable to the ankle during push-off (45-60% of stride time) and the knee in the rebound after collision (12-30% stride). The hip performed increasing amounts of negative work, near the end of stance. Rate of metabolic energy expenditure also increased approximately linearly with load, by approximately 7.6 W for each 1 kg of additional load. The ratio of the increases in work and metabolic cost yielded a relatively constant efficiency of approximately 16%. The metabolic cost not explained by work appeared to be relatively constant with load and did not exhibit a particular trend. Most of the increasing cost for carrying a load appears to be explained by positive mechanical work, especially about the ankle and knee, with both work and metabolic cost increasing nearly linearly with added mass.