The mechanical properties of relaxing muscle
The mechanical properties of relaxing muscle
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放松肌肉的力学特性
DOI：
10.1113/jphysiol.1960.sp006467
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发表时间：
1960
期刊：
影响因子：
--
通讯作者：
D. Wilkie
中科院分区：
文献类型：
--
作者：
B. R. Jewell;D. Wilkie
肌肉对刺激的反应通常分为两个阶段：收缩和放松。肌肉在第一阶段的机械特性已经得到了广泛的研究（参考文献，见Jewell & Wilkie， 1958），人们对张力的产生和做功的方式了解得很多，但对第二阶段的理解却不太清楚。A. V. Hill （1949b）将松弛简单地定义为肌肉的外部机械变化，即“肌肉收缩后恢复到初始长度或张力的过程”。最初，我们对松弛的兴趣是由等张力抽搐和等距抽搐的时间过程之间的显著差异引起的。例如，在图1中，人们面临着一个明显矛盾的情况，即在举起3g的负荷后，肌肉完全放松，而在等长条件下它可以承受5g的张力。不可否认，对于这样的小载荷，情况由于另一个因素而变得复杂，因为在等张情况下，肌肉明显缩短了。然而，即使在大负荷下，等张力缩短少得多，当等距收缩肌肉仍然能够承受相当大的张力时，机械活动显然已经结束。
The response of a muscle to stimulation is classically divided into two phases: contraction and relaxation. The mechanical properties of the muscle in the first phase have been extensively studied (for references, see Jewell & Wilkie, 1958) and much is known about the way in which tension is developed and work is done, but the second phase is much less clearly understood. A. V. Hill (1949b) defined relaxation simply in terms of the external mechanical changes in the muscle, as 'the process by which the muscle returns, after contraction, to its initial length or tension'. Originally our interest in relaxation was aroused by the marked difference between the time courses of isotonic and of isometric twitches. For instance, in Fig. 1, one is confronted by the apparently paradoxical situation that after having lifted a load of 3 g wt. the muscle has completely relaxed at a time when it could have borne tension of 5 g wt. under isometric conditions. Admittedly, with small loads like this, the situation is complicated by an additional factor, for in the isotonic case the muscle has shortened appreciably. However, even with large loads, where the isotonic shortening is much less, mechanical activity has apparently ended at a time when the isometrically contracting muscle is still capable of bearing a considerable tension.