How does passive lengthening change the architecture of the human medial gastrocnemius muscle?
How does passive lengthening change the architecture of the human medial gastrocnemius muscle?
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DOI：
10.1152/japplphysiol.00976.2016
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发表时间：
2017-04-01
影响因子：
3.3
通讯作者：
Herbert, Robert D.
中科院分区：
文献类型：
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作者：
Bolsterlee, Bart;D'Souza, Arkiev;Herbert, Robert D.
很少有关于肌肉结构变化伴随肌肉收缩或肌肉长度变化的全面研究。在这项研究中，我们使用解剖MRI和弥散张量成像（DTI）测量了人内侧腓肠肌在整个肌肉水平、肌束水平和纤维水平的三维结构变化。数据来自8名受试者在放松条件下的3种肌肉长度。在整个肌肉水平上，肌肉腹部长度增加5.1%导致肌肉宽度（平均变化-2.5%）和深度（-4.8%）减少。在肌束水平，对每块肌肉3000个位置进行的肌肉结构测量显示，在松弛长度之上，肌腱长度每增加一毫米，平均肌束长度增加0.46毫米，夹角减少0.27度（浅部0.17度，深层0.37度），肌束曲率减少0.18 m（-1）。没有证据表明，在任何肌肉长度上，沿着肌肉长轴的结构有系统的变化。在纤维水平上，对扩散信号的分析表明，肌肉的被动延长增加了沿纤维的扩散，减少了纤维间的扩散。通过这些跨尺度的测量，我们发现肌纤维、整个肌肉和内侧腓肠肌的腱膜在体内经历的复杂形状变化不能通过简单的几何模型来捕获。这证明需要更复杂的模型，将肌肉纤维的微观结构变化与结构的宏观变化联系起来。新的值得注意的MRI和DTI技术揭示了在被动延长期间人类内侧腓肠肌三维结构的变化。全肌腹部宽度和深度随肌肉长度的增加而减小。在被动延长过程中，肌束长度、旋向和弯曲沿肌肉均匀或接近均匀地变化。水分子在肌肉中的扩散方向与肌束张力方向相同。
There are few comprehensive investigations of the changes in muscle architecture that accompany muscle contraction or change in muscle length in vivo. For this study, we measured changes in the three-dimensional architecture of the human medial gastrocnemius at the whole muscle level, the fascicle level and the fiber level using anatomical MRI and diffusion tensor imaging (DTI). Data were obtained from eight subjects under relaxed conditions at three muscle lengths. At the whole muscle level, a 5.1% increase in muscle belly length resulted in a reduction in both muscle width (mean change -2.5%) and depth (-4.8%). At the fascicle level, muscle architecture measurements obtained at 3,000 locations per muscle showed that for every millimeter increase in muscle-tendon length above the slack length, average fascicle length increased by 0.46 mm, pennation angle decreased by 0.27 degrees (0.17 degrees in the superficial part and 0.37 degrees in the deep part), and fascicle curvature decreased by 0.18 m(-1). There was no evidence of systematic variation in architecture along the muscle's long axis at any muscle length. At the fiber level, analysis of the diffusion signal showed that passive lengthening of the muscle increased diffusion along fibers and decreased diffusion across fibers. Using these measurements across scales, we show that the complex shape changes that muscle fibers, whole muscles, and aponeuroses of the medial gastrocnemius undergo in vivo cannot be captured by simple geometrical models. This justifies the need for more complex models that link microstructural changes in muscle fibers to macroscopic changes in architecture.NEW & NOTEWORTHY Novel MRI and DTI techniques revealed changes in three-dimensional architecture of the human medial gastrocnemius during passive lengthening. Whole muscle belly width and depth decreased when the muscle lengthened. Fascicle length, pennation, and curvature changed uniformly or near uniformly along the muscle during passive lengthening. Diffusion of water molecules in muscle changes in the same direction as fascicle strains.