Caldwell G E, Forrester L W
Department of Kinesiology, University of Maryland, College Park 20742.
Med Sci Sports Exerc. 1992 Dec;24(12):1396-412.
Many studies concerning the mechanical work and efficiency of human motion have used models based on segmental energy. It has been shown theoretically that such work estimates may be in error due to offsetting compensations in power sources underlying the energy profiles. Further, mechanical energy transfers calculated from these energy models have been interpreted as metabolic energy-saving mechanisms. This paper examines the use of mechanical power analysis to calculate work and energy transfer estimates, using the motion of the recovery leg in walking and running for one subject as a demonstrative example. Work and energy transfer estimates from both energy and power models are compared and contrasted. The energy model underestimates the work of the recovery leg in both walking (54% of power model estimate) and running (38%), due to muscle powers at joints opposing each other in energy generation and absorption. Energy transfers calculated with energy models are shown to suffer the same problem of offsetting power sources. In contrast, the power model identifies four energy transfer mechanisms (pendulum, whip, tendon, and joint force transfers), which contribute to energy change within the leg in varying amounts. For the recovery leg, the joint force and whip transfer mechanisms have the greatest magnitude, while the pendulum and tendon transfers are much smaller. These energy transfers can be observed on a time-varying basis throughout a motion sequence and illustrate differences in energy distribution between walking and running. These power-based transfers are discussed in terms of their nature regarding metabolic energy cost and mechanical energy distribution within a multisegmented system. It is suggested that the work and energy transfers calculated from the power analysis are more accurate than those calculated from mechanical energy models and are more useful for understanding performance.
许多关于人体运动的机械功和效率的研究都使用了基于节段能量的模型。从理论上可以看出，由于能量分布背后的动力源存在抵消补偿，这种功的估计可能会出现误差。此外，从这些能量模型计算出的机械能转移被解释为代谢节能机制。本文以一名受试者行走和跑步时摆动腿的运动为例，研究了使用机械功率分析来计算功和能量转移估计值的方法。对能量模型和功率模型的功和能量转移估计值进行了比较和对比。能量模型低估了摆动腿在行走（功率模型估计值的54%）和跑步（38%）时的功，这是由于关节处的肌肉力量在能量产生和吸收过程中相互对抗。结果表明，用能量模型计算的能量转移也存在动力源抵消的问题。相比之下，功率模型识别出四种能量转移机制（摆动、鞭打、肌腱和关节力转移），它们对腿部能量变化的贡献各不相同。对于摆动腿来说，关节力和鞭打转移机制的幅度最大，而摆动和肌腱转移则小得多。这些能量转移可以在整个运动序列中随时间变化观察到，并说明了行走和跑步之间能量分布的差异。本文从这些基于功率的转移在代谢能量消耗和多节段系统内机械能分布方面的性质进行了讨论。研究表明，通过功率分析计算出的功和能量转移比通过机械能模型计算出的更准确，并且对于理解运动表现更有用。
