Neural Mechanisms in Muscle Fatigue

肌肉疲劳的神经机制

基本信息

批准号：
7435201
负责人：
ROGER M. ENOKA
金额：
$ 23.96万
依托单位：
UNIVERSITY OF COLORADO
依托单位国家：
美国
项目类别：
财政年份：
2002
资助国家：
美国
起止时间：
2002-04-15 至 2010-05-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The time to task failure for an isometric contraction with the elbow flexor muscles is twice as long when an individual sustains a submaximal force (force task) compared with maintaining a constant limb position while supporting an equivalent inertial load (position task). Although the net muscle torque generated by each subject is identical for the two tasks, indirect measurements indicate that central neural activity increases more rapidly during the position task. Furthermore, work completed in the initial cycle of this award has suggested that a difference in the time to task failure can exist without significant differences in inhibitory inputs, but that these inputs augment the difference in time to failure for the two tasks. Our model is that the position task involves reduced activation of the interneurons that are responsible for presynaptic inhibition of the feedback transmitted by group la afferents. Such suppression of presynaptic inhibition, which is modulated by both descending drive and feedback from peripheral afferents, will result in heightened excitation of the spinal motor neurons during the position task. We hypothesize that the position task is associated with greater net excitation from spinal and supraspinal sources, resulting in earlier recruitment of a finite pool of motor units and premature task failure. According to this hypothesis, the difference in the time to task failure is attributable to differences in the input received by the spinal motor neurons. We propose a research plan that will quantify the change in excitability of single motor units (Aim 1), compare the inputs that the spinal motor neurons receive from corticospinal neurons (Aim 2) and group la afferents of muscle spindles (Aims 3-4). and determine the level of activity in accessory muscles (Aim 5) during the two tasks. The experiments on the corticospinal neurons and the group la reflex pathway will involve evoked responses and will be performed in collaboration with Prof. Duchateau in Brussels. The outcomes will provide novel information on the physiological adjustments that occur during isometric contractions, which are the most common form of muscle activity, and will have direct application to the design of work tasks in ergonomics and the prescription of physical activities in rehabilitation.

描述（由申请人提供）：当个人维持次最大力（力任务）时，与在支撑等效惯性负载时保持恒定的肢体位置相比，肘屈肌等长收缩的任务失败时间是前者的两倍（定位任务）。尽管两个任务中每个受试者产生的净肌肉扭矩是相同的，但间接测量表明中枢神经活动在位置任务期间增加得更快。此外，在该奖项的初始周期中完成的工作表明，在抑制输入没有显着差异的情况下，任务失败时间可能存在差异，但这些输入会增加两项任务失败时间的差异。我们的模型是，位置任务涉及减少中间神经元的激活，这些中间神经元负责突触前抑制由组la传入神经传递的反馈。这种突触前抑制的抑制是由下行驱动和周围传入神经的反馈调节的，将导致位置任务期间脊髓运动神经元的兴奋增强。我们假设位置任务与来自脊髓和脊髓上源的更大的净兴奋相关，导致有限的运动单位的早期募集和过早的任务失败。根据这一假设，任务失败时间的差异可归因于脊髓运动神经元接收到的输入的差异。我们提出了一项研究计划，该计划将量化单个运动单位兴奋性的变化（目标 1），比较脊髓运动神经元从皮质脊髓神经元接收的输入（目标 2）和肌梭的 la 组传入神经元（目标 3-4）。并确定这两项任务期间辅助肌肉的活动水平（目标 5）。关于皮质脊髓神经元和群反射通路的实验将涉及诱发反应，并将与布鲁塞尔的 Duchateau 教授合作进行。研究结果将提供有关等长收缩期间发生的生理调整的新信息，等长收缩是最常见的肌肉活动形式，并将直接应用于人体工程学中的工作任务设计和康复中身体活动的规定。