Herzog Walter
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB T2N 1N4, Canada.
J Sport Health Sci. 2018 Jul;7(3):255-264. doi: 10.1016/j.jshs.2018.05.005. Epub 2018 Jun 2.
It is well acknowledged that muscles that are elongated while activated (i.e., eccentric muscle action) are stronger and require less energy (per unit of force) than muscles that are shortening (i.e., concentric contraction) or that remain at a constant length (i.e., isometric contraction). Although the cross-bridge theory of muscle contraction provides a good explanation for the increase in force in active muscle lengthening, it does not explain the residual increase in force following active lengthening (residual force enhancement), or except with additional assumptions, the reduced metabolic requirement of muscle during and following active stretch. Aside from the cross-bridge theory, 2 other primary explanations for the mechanical properties of actively stretched muscles have emerged: (1) the so-called sarcomere length nonuniformity theory and (2) the engagement of a passive structural element theory. In this article, these theories are discussed, and it is shown that the last of these-the engagement of a passive structural element in eccentric muscle action-offers a simple and complete explanation for many hitherto unexplained observations in actively lengthening muscle. Although by no means fully proven, the theory has great appeal for its simplicity and beauty, and even if over time it is shown to be wrong, it nevertheless forms a useful framework for direct hypothesis testing.
人们普遍认为，在激活状态下被拉长的肌肉（即离心肌肉动作）比正在缩短的肌肉（即向心收缩）或保持恒定长度的肌肉（即等长收缩）更强壮，且（每单位力量）消耗的能量更少。尽管肌肉收缩的横桥理论很好地解释了主动肌肉拉长时力量的增加，但它无法解释主动拉长后力量的残余增加（残余力量增强），或者除了额外假设外，无法解释主动拉伸期间及之后肌肉代谢需求的降低。除了横桥理论外，对于主动拉伸肌肉的力学特性还出现了另外两种主要解释：（1）所谓的肌节长度不均匀理论和（2）被动结构元件参与理论。在本文中，将对这些理论进行讨论，并表明其中最后一种理论——被动结构元件在离心肌肉动作中的参与——为主动拉长肌肉中许多迄今无法解释的现象提供了一个简单而完整的解释。尽管该理论远未得到充分证明，但因其简单性和合理性而极具吸引力，即使随着时间推移被证明是错误的，它仍然构成了一个用于直接假设检验的有用框架。
