MUSCLE PROPERTIES DURING NORMAL MOVEMENT CONDITIONS

肌肉将神经信号转化为运动所需的力量。 每一块肌肉都由大量的运动单位组成，每个运动单位 它只产生很小的力。几乎所有以前的工作都在 电机单元属性取决于等轴测条件(恒定 肌肉长度)，以便于测量这些细小的力。然而， 等轴测条件只占正常电机的一小部分 行为。此外，来自整体肌肉和单个肌肉纤维的数据 已经表明肌肉组织具有广泛的动态行为。这个 这项建议的目标是获得第一个系统的测量结果 动态电动机组属性。 虽然有许多动态特性可以单独研究 单位，具体目标1建议确定哪些电机单位的属性 在正常的运动条件下实际上很重要。例如，大多数 肌肉模型仅依赖于肌肉的稳态属性，因此 假设动态特性在力的生成中起次要作用。一种新的 已经开发了分解技术来检验这一假设。它 有两个阶段：(1)精确测量单个电机单元的技术 动态状态下的力与正常运动状态下的力相似；以及 (2)在更受控制的条件下进行测量，旨在 确定每个机械特性对单位力输出的影响 在那些正常的运动条件下。 具体目标2和3侧重于运动单位作为一个群体的行为 平行的机械元件。由于马达单元形成了一个异类 按单位力量递增顺序被激活的人口， 人口行为不能从任何单个单位的行为中预测出来。 需要检验的假设是，人口行为增加了 肌肉的稳定性(即对扰动的抵抗力)。这个 检验这一假设的技术也有两个阶段：(1)测量 在对稳定性有很大影响的2个基本电机单元属性中， 力-速度和力-长度关系；和(20预测 用真实感计算机模拟种群的力-速-长行为 基于这些单个单元数据的模拟。 这些数据应该为理解潜在的 影响双侧运动的疾病中功能缺陷的机制 以及中枢神经系统对发动机单元的控制。

Muscles transduce neural signals into the forces needed for movement. Every muscle is composed of a large population of motor units, each of which generates only a very small force. Virtually all previous work on motor unit properties has relied upon isometric conditions (constant muscle length) to facilitate measurement of these small forces. However, isometric conditions constitute only a small portion of normal motor behavior. Furthermore, data from whole muscles and single muscle fibers have shown that muscle tissue has a wide range of dynamic behaviors. The goal of this proposal is to obtain the first systematic measurements of dynamic motor unit properties. While there are many dynamic properties that could be studied in single units, Specific aim 1 proposes to determine which motor unit properties are actually important in normal movement conditions. For example, most muscle models rely only on the steady-state properties of muscle and thus assume dynamic properties play a minor role in force generation. A new decomposition technique has been developed to test this hypothesis. It has 2 phases: (1) techniques for accurately measuring single motor unit forces in dynamic conditions resembling those in normal movements; and (2) measurements in more controlled conditions that are designed to identify the effect of each mechanical property on the unit force output in those normal movement conditions. Specific aims 2&3 focus upon the behavior of motor units as a population of parallel mechanical elements. Since motor units form a heterogeneous population that is activated in order of increasing unit force, the population behavior cannot be predicted from that of any single unit. The hypothesis to be tested is that the population behavior increases the stability of muscle (i.e. its resistance to perturbations). The technique for testing this hypothesis also has 2 phases: (1) measurement of 2 basic motor unit properties that greatly influence stability, the force-velocity and force-length relations; and (20 prediction of population force-velocity-length behavior by use of realistic computer simulations based on these single unit data. These data should provide a foundation for understanding the underlying mechanisms of the functional deficits in diseases affecting both motor units and the control of motor units by the CNS.