Influence of tendon elasticity on muscle-tendon contractile element mechanics

项目概述：肌腱的弹性能量储存和返回可以节省大量的代谢能量，但可能需要精确的时间和大小的肌肉力量模式。神经肌肉和神经损伤（如中风、脊髓损伤、脑瘫）和动力下肢机器人辅助装置可导致运动过程中肌肉力量输出模式的改变。本研究的主要目的是研究在肌肉力量输出减少的情况下，肌腱弹性如何影响肌肉-肌腱单元的收缩元件的力学。该项目将使用孤立的肌肉肌腱准备和建模，以测试关于肌腱在循环收缩期间调节肌肉工作中的作用的几个假设。具体目的是：(1)表明在拉伸-缩短收缩过程中，收缩单元功不随肌肉力的比例而减少；(2)确定相对肌腱柔度（即肌腱长度与肌肉-肌腱长度之比）对肌肉-肌腱收缩单元力-功关系的影响。在体外实验中，将使用一种新型的声学测量法和肌肉测量学相结合的方法来分离牛蛙（Rana catesbeiana L.）跖长肌-跟腱在受控拉伸-缩短过程中肌肉和跟腱的力学行为。为了补充体外实验，我将建立一个等效的肌肉-肌腱单元的计算机模拟。非线性方程将描述收缩单元的力长、力速度和力激活特性，线性弹簧将表示系列弹性单元。将实证方法与理论方法相结合的基本原理是：(1)肌肉-肌腱模型可以做出预测，并通过精心设计的体外实验进行验证；(2)肌肉-肌腱的体外实验可以帮助测试模型简化的有效性。拟议的研究将发展肌肉生理学和非线性计算建模的技能，这对我未来开发仿生下肢辅助装置的研究计划将是无价的。相关性：对综合肌肉-肌腱功能的基本理解对于解决与人类健康相关的问题具有重要意义。该计划将吸引临床医生、生理学家、生物力学家和工程师的跨学科兴趣。研究结果将(1)有助于制定限制肌肉力量产生的神经和肌肉骨骼疾病的康复策略(2)有助于改进假肢和矫形器的设计，以辅助下肢步态。

DESCRIPTION (provided by applicant): Project Summary: Elastic energy storage and return in tendons can save significant metabolic energy, but likely requires muscle force patterns with precise timing and magnitude. Neuromuscular and neurological impairments (e.g. stroke, spinal cord injury, cerebral palsy) and powered lower-limb robotic assistive devices can lead to altered patterns of muscle force output during locomotion. The broad goal of this research is to examine how tendon elasticity effects the mechanics of the contractile element of the musle-tendon unit under conditions of reduced muscle force output. The project will use an isolated muscle-tendon preparation and modeling, to test several hypotheses about the role of tendons in modulating muscle work during cyclic contraction. The specific aims are to (1) show that contractile element work does not decrease in proportion to muscle force during stretch-shorten contractions and (2) determine the effect of relative tendon compliance (i.e. the ratio of tendon length to muscle-tendon length) on the force-work relationship of the contractile element of muscle-tendon. The in vitro experiments will use a novel combination of sonomicrometry and muscle ergometry to separate the mechanical behavior of the muscle from the tendon during controlled stretch-shortening of bullfrog (Rana catesbeiana L.) plantaris longus muscle-Achilles tendon. To complement the in vitro experiments I will build an equivalent computer simulation of the muscle- tendon unit. Non-linear equations will characterize the force-length, force-velocity and force-activation properties of the contractile element and a linear spring will represent the series-elastic element. The rationale behind combining empirical and theoretical approaches is that (1) the muscle-tendon model can make predictions to be tested with carefully designed in vitro experiments and (2) the in vitro experiments on muscle-tendon can help test the validity of model simplifications. The proposed research will develop skills in both muscle physiology and non-linear computational modeling that will be invaluable to my future research program to develop bio-inspired lower limb assistive devices. Relevance: A fundamental understanding of integrated muscle-tendon function has important implications for solving problems relevant to human health. The proposed project will attract interdisciplinary interest from clinicians, physiologists, biomechanists, and engineers. The results will (1) aid in developing strategies for the rehabilitation of neurological and musculoskeletal disorders that limit muscle force production (2) contribute to improved design of prostheses and orthoses intended to assist the lower-limb during gait.