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，肌肉力量的缓慢产生在预防跌倒方面特别重要。运动单元研究迫切需要扩展范式，以提供有关现实任务中控制机制的新信息。我们将研究两种相关运动单位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人群运动质量的信息。目的1是关于正弦等长收缩精确控制中的速率编码。据推测，在老年人中，放电率调制的幅度较小，这可能是由于收缩性减慢的老年肌纤维的抽搐总和增强。目的2是关于运动单位放电行为在快速生产力从休息以及从一个次最大的力量水平。据推测，在开始快速收缩期间，与年轻成人相比，老年运动单位的初始放电速率将较慢，并且双峰放电将较少。将从20名年轻人（<30岁）和20名老年人（>65岁）的第一背侧骨间肌获得运动单位和肌力记录、表面肌电图和收缩特性。在这些条件下成功的实验可以被认为是运动单位研究的重大进展。除了进一步了解正常老化的水平上的运动单位，这个项目将提供大量的新信息，运动单位放电行为一般。例如：1）该规范性数据对于患者群体中的类似研究的价值，以及2）更好地了解健康个体中的神经命令可以帮助改善瘫痪肌肉的功能性电刺激。该项目还为未来研究这些神经因素的适应性和老年人和患者人群的功能提供了基础。

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.