Functional diversification within and between muscle synergists during locomotion
Functional diversification within and between muscle synergists during locomotion
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DOI：
10.1098/rsbl.2007.0472
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发表时间：
2008-02-23
期刊：
影响因子：
3.3
通讯作者：
Wakeling, James M.
中科院分区：
文献类型：
--
作者：
Higham, Timothy E.;Biewener, Andrew A.;Wakeling, James M.
运动源于肢体肌肉复杂而协调的功能。然而，对于以不同速度或在可变地形上移动的动物来说，肌肉功能在单个步幅和步幅之间是动态的。虽然很明显，运动单位的募集可以在肌肉之间和肌肉内变化，但我们对在体内条件下肌肉内和肌肉之间如何分配功知之甚少。在这里，我们表明，外侧腓肠肌（LG）的盔珠鸡（Numida agris）执行更多的工作比其前，内侧腓肠肌（MG）和MG（pMG）的近端区域执行更多的工作比远端区域（dMG）。当鸟以0.5 m s（-1）的速度行走时，LG所做的正功大约是近端MG的两倍，而当以2.0 m s（-1）的速度奔跑时，LG所做的正功大约是近端MG的四倍。这可能是由于膝关节的不同时刻以及运动单位募集的差异。dMG比pMG做的功少，因为它的表观动态刚度更大，而且它表现出更大的慢缩纤维募集。pMG的更大顺应性导致在力开始时其纤维束的拉伸增加，从而进一步增强力的产生。我们的研究结果表明，肌肉协同之间和内部的功能多样性的能力，随着步态和速度的变化而增加。
Locomotion arises from the complex and coordinated function of limb muscles. Yet muscle function is dynamic over the course of a single stride and between strides for animals moving at different speeds or on variable terrain. While it is clear that motor unit recruitment can vary between and within muscles, we know little about how work is distributed within and between muscles under in vivo conditions. Here we show that the lateral gastrocnemius (LG) of helmeted guinea fowl (Numida meleagris) performs considerably more work than its synergist, the medial gastrocnemius (MG) and that the proximal region of the MG (pMG) performs more work than the distal region (dMG). Positive work done by the LG was approximately twice that of the proximal MG when the birds walked at 0.5 m s(-1), and four times when running at 2.0 m s(-1). This is probably due to different moments at the knee, as well as differences in motor unit recruitment. The dMG performed less work than the pMG because its apparent dynamic stiffness was greater, and because it exhibited a greater recruitment of slow-twitch fibres. The greater compliance of the pMG leads to increased stretch of its fascicles at the onset of force, further enhancing force production. Our results demonstrate the capacity for functional diversity between and within muscle synergists, which increases with changes in gait and speed.