MECHANICAL INTERACTIONS OF MOTOR UNITS

运动单元的机械相互作用

• 批准号: 2269529
• 负责人: RANDALL K POWERS
• 金额: $ 7.94万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-01-01 至 1996-12-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2269529
• 关键词: afferent nerve; cats; dorsal root; electrodes; electromyography; electrostimulus; evoked potentials; mechanical pressure; motor neurons; muscle function; muscle tension; single cell analysis; tendons

Mechanical models of whole muscle-tendon complexes often assume that individual muscle fiber-tendon fiber units act independently. With few exceptions, previous experimental analyses of muscle function have been based on studies of single isolated muscle fibers, activation of single motor units or activation of all the motor units of a muscle. However, under physiological conditions, muscle force is graded by recruiting variable numbers of motor units and modulating the firing rate of those motor units. The total force produced by the muscle depends not only on the intrinsic properties of the motor units but also upon mechanical interactions between motor units. In fact, significant mechanical linkages between separate motor units may arise both from links between the tendinous strands into which their fibers insert and from connective tissue links between adjacent muscle fibers. The goal of the research projects proposed in this application is to quantify the mechanical interactions between the motor units within a single muscle and to explore the mechanisms of these interactions. Two types of mechanical interactions between motor units have been previously described: (1) nonlinear summation of individual motor unit tensions, where the tension produced by concurrently activated units is greater than the linear sum of their individual tensions, and (2) "force- assistance", where the tension produced by a motor unit is enhanced following the superimposed activation and deactivation of another unit. The former effect has been attributed to a reduction of frictional forces between active and passive muscle fibers, while the latter effect may depend upon the internal length changes produced by motor unit activation. The specific aims of the proposed experiments are to further investigate the phenomena of nonlinear summation and force assistance by addressing the following questions: 1. What is the source and nature of internal friction between active and passive muscle fibers? 2. Is force assistance due to internal length changes produced by activation of motor units? 3. How are the magnitudes of nonlinear force summation and force assistance related to numbers of motor units activated, tendon compliance, motor unit type and muscle architecture?

整个肌肉弯曲复合物的机械模型通常认为 单个肌肉纤维纤维纤维单元独立起作用。很少 例外，先前对肌肉功能的实验分析已经 基于对单个孤立肌肉纤维的研究，激活了单个 肌肉的所有电动机单元的运动单位或激活。然而， 在生理条件下，肌肉力是通过招募来分级的 可变数量的电动机单元并调节那些电动机的发射速率 电机单元。肌肉产生的总力不仅取决于 电机单元的固有特性，但也具有机械性能 电机单元之间的相互作用。实际上，重要的机械链接 单独的电动机单元之间可能来自 其纤维纤维插入并从结缔组织中 相邻肌肉纤维之间的组织联系。研究的目标 本应用程序提出的项目是量化机械的 单个肌肉中的电机单元之间的相互作用并探索 这些相互作用的机制。 电机单元之间的两种机械相互作用已经 先前描述的：（1）单个电机单元的非线性求和 紧张局势，同时激活单位产生的张力是 大于其各个紧张局势的线性总和，（2）“力 - 援助”，在增强电动机产生的张力的情况下 在另一个单元的叠加激活和停用后。 前者的效果归因于减少摩擦力 在活性和被动肌肉纤维之间，而后者的效果可能 取决于电动机激活产生的内部长度变化。 提出的实验的具体目的是进一步研究 非线性总和和力援助的现象通过解决 以下问题： 1。主动与内部摩擦的来源和性质是什么 被动肌纤维？ 2。是由于内部长度变化而产生的力辅助 电机单元的激活？ 3。非线性力总和和力的幅度如何 与激活的电动机数量相关的辅助，肌腱合规性， 运动单元类型和肌肉建筑？