Motor Unit Discharge and Slowed Motor Output in Elderly

描述（由申请人提供）：老年人在执行精确任务时经常因控制能力差而感到沮丧，肌肉力量产生缓慢在预防跌倒中具有特殊的重要性。运动单元研究迫切需要扩展范式，以提供关于现实世界任务中控制机制的新信息。我们将研究两种相关运动单元放电行为的年龄相关差异，并提供可用于改善老年人和患者群体运动质量的信息。目标1是关于精确控制正弦等距收缩过程中的速率编码。据推测，老年人的放电速率调节幅度较小，这可能是由于衰老肌纤维的抽搐总和增强而收缩性减慢。目标2是关于运动单元放电行为在快速力量生产从休息和从次最大的力量水平。据推测，在快速收缩开始时，老年运动单元的初始放电速率将较慢，与年轻人相比，将有更少的双重放电。运动单位和肌肉力记录、表面肌电图和收缩特性将从20名年轻（<30岁）和20名老年（60 ~ 65岁）成人的第一背骨间肌中获得。在这些条件下成功的实验可以被认为是运动单元研究的重大进展。除了进一步了解电机单元水平的正常老化外，该项目还将提供有关电机单元放电行为的大量新信息。例如：1)对病人群体进行类似研究的规范性数据的价值，2)更好地了解健康个体的神经命令可以帮助改善瘫痪肌肉的功能性电刺激。该项目也为今后研究这些神经因子和功能在老年人和患者群体中的适应性提供了基础。

DESCRIPTION (provided by applicant): The elderly are often frustrated by poor control during precision tasks, and slower production of muscular force has specific importance in fall prevention. Motor unit research is in dire need of expanded paradigms to provide new information about control mechanisms during real-world tasks. We will examine age-related differences in two relevant motor unit discharge behaviors and provide information that can be used to improve movement quality in older adults and also in patient populations. Aim 1 is about rate coding during the precise control of sinusoidal isometric contractions. It is hypothesized that that the amplitude of firing rate modulation is less in older adults, perhaps due to enhanced twitch summation of aged muscle fibers with slowed contractility. Aim 2 is about motor unit discharge behavior during rapid force production from rest as well as from a submaximal force level. It is hypothesized that during the initiation of rapid contractions, the initial firing rates of aged motor units will be slower and there will be fewer doublet discharges, as compared to young adults. Motor unit and muscular force recordings, surface electromyography and contractile properties will be obtained from the first dorsal interosseous muscle of 20 young (<30 years) and 20 older (>65 years) adults. Successful experiments in these conditions can be considered significant progress in motor unit research. In addition to furthering knowledge of normal aging at the level of the motor unit, this project will provide vast new information about motor unit discharge behavior in general. Consider for example: 1) the value of this normative data for similar research in patient populations, and 2) a better knowledge of neural commands in healthy individuals can help to improve the functional electrical stimulation of paralyzed muscle. This project also provides the basis for future research on the adaptability of these neural factors and function in older adults and patient populations.