Task Dependence of Muscle Fatigue in Older Adults

描述(由申请人提供)：NIA先导研究计划，主题14：感觉和运动处理肌肉的耐力能力将随着所执行的任务而变化。然而，在老年人中，神经肌肉系统中与年龄相关的变化对肌肉疲劳的任务依赖性性质的影响尚未被探索。这就引出了以下问题：年龄是否会改变神经肌肉系统适应不同疲劳任务的能力？在年轻人中，当保持力量并推向力传感器(力任务)时，进行次最大等长收缩时的耐力时间比保持恒定肘角同时在手腕上支撑同等惯性载荷(位置任务)时的耐力时间更长(Hunter等人)。2002年)。体位任务的较短耐力时间归因于神经机制，包括更快的下降驱动速度。鉴于神经肌肉系统中与年龄相关的变化将使老年人在疲劳任务期间容易受到神经系统内的损害，这一R03应用程序检验了以下假设：由于神经机制中与年龄相关的损害，在姿势任务中，次最大疲劳收缩的耐力时间与力量任务相比，老年人与年轻人相比将更大。有三个具体的目的来检验这一假设。第一个目标是比较年轻人和老年人在姿势任务和力量任务中肘屈肌的耐力时间和肌肉激活模式。目标2和目标3将通过测量疲劳收缩期间肌肉的下行驱动和外周传入反馈指数，来评估两项任务中肌肉疲劳与年龄相关的差异的潜在机制。这些测量包括肌肉交感神经活动、心率、运动输出的波动、劳力感和升压反应。这项申请提出了一种新的方法来检查老年人的肌肉疲劳。这些发现将提供关于老年人在日常任务中更喜欢进行持续时间较长的次极量任务的负荷和支持类型的初步信息。这将构成关于老年人肌肉疲劳的任务依赖性本质的新信息。这些初步发现将为RO 1的应用奠定基础，该应用将进一步探索老年人肌肉疲劳的机制和对任务的依赖性。

DESCRIPTION (provided by applicant): NIA Pilot Research Program, Topic 14: Sensory and Motor Processing The endurance capacity of a muscle will vary with the task performed. However, the influence of age-related changes within the neuromuscular system on the task-dependent nature of muscle fatigue is unexplored in older adults. This raises the following question: Does age alter the ability of the neuromuscular system to adapt to different fatiguing tasks? In young adults, the endurance time when performing a submaximal isometric contraction was longer when maintaining a force and pushing against a force transducer (force task) compared with maintaining a constant elbow angle while supporting an equivalent inertial load at the wrist (position task) (Hunter et al. 2002). The briefer endurance time for the position task was attributable to neural mechanisms including a greater rate of descending drive. Given that age-related changes in the neuromuscular system will predispose the older adult to impairment within the nervous system during a fatiguing task, this RO3 application examines the following hypothesis: the difference in endurance time of a submaximal fatiguing contraction for a position task compared with a force task, will be greater in older adults compared with young adults due to age-related impairment in neural mechanisms. There are three specific aims to test this hypothesis. The first aim will compare the endurance time and muscle activation patterns of the elbow flexor muscles in young and older adults for a position task and force task. Aims 2 and 3 will evaluate potential mechanisms for the age-related differences in muscle fatigue of the two tasks, by measuring indices of descending drive and peripheral afferent feedback from the muscle during the fatiguing contractions. These measures include muscle sympathetic nerve activity, heart rate, fluctuations in motor Output, sense of effort and the pressor response. This application proposes a novel approach to examine muscle fatigue in older adults. The findings will provide preliminary information on the type of load and support preferred by older adults for long-duration submaximal tasks during daily tasks. This will constitute new information on the task-dependent nature of muscle fatigue in older adults. These preliminary findings will form the foundation for an RO 1 application that will further explore the mechanisms and task dependency of muscle fatigue in older adults.