肌肉收缩的能量。I.等长收缩过程中的组织力和变形
The energy of muscle contraction. I. Tissue force and deformation during isometric contractions
摘要：
在收缩过程中，由于ATP水解产生的能量，肌肉组织的能量增加。这种能量作为可收缩元件中的应变能势、来自基础材料组织的3D变形（包含细胞和ECM效应）的应变能势、与肌肉几乎不可压缩的体积的变化相关的能量以及在肌肉表面进行的外部功而分布在整个组织中。因此，当肌肉收缩时，能量通过肌肉组织重新分配，只有一部分能量用于做机械功并在肌肉的作用线中产生力。了解应变能势如何在肌肉组织中重新分布，将有助于揭示为什么整个肌肉在其作用线上的机械性能与预期的收缩元件单独的性能不匹配。在这里，我们使用基于有限元方法的3D肌肉模型来演示这些物理效果。收缩肌肉内的组织变形是大的，并且因此使用大变形的连续介质力学的原理来解释收缩的力学。我们提出了模拟的收缩内侧腓肠肌，显示组织变形，从基于MRI的图像镜像观察。本文跟踪通过肌肉组织在等长收缩过程中的应变能电位的重新分配，并显示如何纤维缩短，pennation角，横向膨胀和各向异性的应力和应变的肌肉组织都与肌肉的材料特性和收缩元件的作用之间的相互作用。
英文摘要：
During contraction the energy of muscle tissue increases due to energy from the hydrolysis of ATP. This energy is distributed across the tissue as strain-energy potentials in the contractile elements, strain-energy potential from the 3D deformation of the base-material tissue (containing cellular and ECM effects), energy related to changes in the muscle's nearly incompressible volume and external work done at the muscle surface. Thus, energy is redistributed through the muscle's tissue as it contracts, with only a component of this energy being used to do mechanical work and develop forces in the muscle's line-of-action. Understanding how the strain-energy potentials are redistributed through the muscle tissue will help enlighten why the mechanical performance of whole muscle in its line-of-action does not match the performance that would be expected from the contractile elements alone. Here we demonstrate these physical effects using a 3D muscle model based on the finite element method. The tissue deformations within contracting muscle are large, and so the mechanics of contraction were explained using the principles of continuum mechanics for large deformations. We present simulations of a contracting medial gastrocnemius muscle, showing tissue deformations that mirror observations from MRI-based images. This paper tracks the redistribution of strain-energy potentials through the muscle tissue during isometric contractions, and shows how fibre shortening, pennation angle, transverse bulging and anisotropy in the stress and strain of the muscle tissue are all related to the interaction between the material properties of the muscle and the action of the contractile elements.
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