Mörl Falk, Siebert Tobias, Häufle Daniel
Forschungsgesellschaft für Angewandte Systemsicherheit und Arbeitsmedizin mbH, Zentrum für Bewegungstherapie, Dubliner Strasse 12, 99091, Erfurt, Germany.
Institute of Sport and Motion Science, University of Stuttgart, 70569, Stuttgart, Germany.
Biomech Model Mechanobiol. 2016 Feb;15(1):245-58. doi: 10.1007/s10237-015-0688-7. Epub 2015 Jun 4.
Experimental studies show different muscle-tendon complex (MTC) functions (e.g. motor or spring) depending on the muscle fibre-tendon length ratio. Comparing different MTC of different animals examined experimentally, the extracted MTC functions are biased by, for example, MTC-specific pennation angle and fibre-type distribution or divergent experimental protocols (e.g. influence of temperature or stimulation on MTC force). Thus, a thorough understanding of variation of these inner muscle fibre-tendon length ratios on MTC function is difficult. In this study, we used a hill-type muscle model to simulate MTC. The model consists of a contractile element (CE) simulating muscle fibres, a serial element (SE) as a model for tendon, and a parallel elastic element (PEE) modelling tissue in parallel to the muscle fibres. The simulation examines the impact of length variations of these components on contraction dynamics and MTC function. Ensuring a constant overall length of the MTC by L(MTC) = L(SE) + L(CE), the SE rest length was varied over a broad physiological range from 0.1 to 0.9 MTC length. Five different MTC functions were investigated by simulating typical physiological experiments: the stabilising function with isometric contractions, the motor function with contractions against a weight, the capability of acceleration with contractions against a small inertial mass, the braking function by decelerating a mass, and the spring function with stretch-shortening cycles. The ratio of SE and CE mainly determines the MTC function. MTC with comparably short tendon generates high force and maximal shortening velocity and is able to produce maximal work and power. MTC with long tendon is suitable to store and release a maximum amount of energy. Variation of muscle fibre-tendon ratio yielded two peaks for MTC's force response for short and long SE lengths. Further, maximum work storage capacity of the SE is at long relL(SE,0). Impact of fibre-tendon length ratio on MTC functions will be discussed. Considering a constant set of MTC parameters, quantitative changes in MTC performance (work, stiffness, force, energy storage, dissipation) depending on varying muscle fibre-tendon length ratio were provided, which enables classification and grading of different MTC designs.
实验研究表明，根据肌纤维与肌腱的长度比，肌肉 - 肌腱复合体（MTC）具有不同的功能（如运动功能或弹性功能）。在比较通过实验研究的不同动物的不同MTC时，提取的MTC功能会受到例如MTC特定的羽状角、纤维类型分布或不同的实验方案（如温度或刺激对MTC力的影响）的偏差影响。因此，很难全面了解这些内部肌纤维 - 肌腱长度比的变化对MTC功能的影响。在本研究中，我们使用了一个希尔型肌肉模型来模拟MTC。该模型由模拟肌纤维的收缩元件（CE）、作为肌腱模型的串联元件（SE）以及与肌纤维平行建模组织的平行弹性元件（PEE）组成。该模拟研究了这些组件的长度变化对收缩动力学和MTC功能的影响。通过L(MTC) = L(SE) + L(CE)确保MTC的总长度恒定，SE的静息长度在从0.1到0.9 MTC长度的广泛生理范围内变化。通过模拟典型的生理实验研究了五种不同的MTC功能：等长收缩的稳定功能、对抗重量收缩的运动功能、对抗小惯性质量收缩的加速能力、使质量减速的制动功能以及具有拉伸 - 缩短循环的弹性功能。SE和CE的比例主要决定MTC功能。肌腱相对较短的MTC产生高力和最大缩短速度，并且能够产生最大的功和功率。肌腱较长的MTC适合存储和释放最大量的能量。肌纤维 - 肌腱比的变化在短和长SE长度时产生了MTC力响应的两个峰值。此外，SE的最大功存储能力在长relL(SE,0)时出现。将讨论纤维 - 肌腱长度比对MTC功能的影响。考虑到一组恒定的MTC参数，提供了根据变化的肌纤维 - 肌腱长度比的MTC性能（功、刚度、力、能量存储、耗散）的定量变化，这使得能够对不同的MTC设计进行分类和分级。
