Motor Unit Activity and Force Steadiness Changes w Aging

描述(由申请人提供)： 在衰老过程中，神经肌肉系统会经历严重的失神经和肌肉萎缩。肌肉力量的产生变得不那么稳定，特别是在肌肉力量的受控释放和低力量收缩期间。失去对手部灵巧性的控制对许多老年人的生活质量和那些因肌肉骨骼疾病而导致的废用性萎缩的影响是极其不利的。这项研究将探讨衰老过程中手部稳定性下降的可能机制。 我们假设，老年人运动神经元中有更高的自我维持放电的发生率，这一行为导致了肌肉力量平稳释放的难度增加。其次，我们假设，在老年人中，拇指和食指肌肉的运动单位同步性和连贯性增加，这可以解释在诸如捏手指等功能性手任务中观察到的稳定性下降的原因。最后，我们将确定拇指和食指运动单位放电率的同步性和连贯性的变化是否与老年人阻力训练后力量稳定性的增加有关。 这项研究将包括在为期一个月的培训计划之前和之后进行的两组实验。第一项研究将调查年轻人和老年人在拇指和食指独立收缩时，单个运动单位的发射率和拇指和食指肌肉的自我维持放电的发生率。在第二组实验中，所有受试者都将执行握力-准确性任务，并通过交叉相关分析比较年轻人和老年人拇指和食指之间的同步性和一致性程度。20名老年人将被分成两组，接受为期四周的不同训练计划。其中一组将进行带回家的阻力训练计划，而另一组将进行精确的运动学习计划。训练结束后，将再次测量单个运动单元的自持性发射的发生率和运动单元的发射速率、挤压时的同步性和一致性。对使手稳定的神经肌肉机制的阐明将为设计先进的康复系统提供基础。

DESCRIPTION (provided by applicant): The neuromuscular system undergoes significant denervation and muscle atrophy during aging. Muscle force production becomes less steady, particularly during the controlled release of muscle force and during low-force contractions. The loss of control of hand dexterity is extremely detrimental to the quality of life in many older individuals and to those affected by disuse atrophy from musculoskeletal disease. This study will investigate possible mechanisms behind the decrease in hand steadiness during aging. We hypothesize that there is a higher incidence of self sustained firing in motoneurons of older adults and that this behavior contributes to the increased difficultly to release muscle force smoothly. Secondly, we hypothesize that there is an increase in motor unit synchronization and coherence across the muscles of the thumb and index finger in older adults and that this could account for the decrease in steadiness observed during functional hand tasks such as pinching. Finally, we will determine if changes in motor unit firing rate synchronization and coherence across the thumb and index finger are related to increases in force steadiness following resistance training in older adults. This study will encompass two sets of experiments performed before and after one-month training programs. The first will investigate single motor unit firing rates and the incidence of self sustained firing of muscles serving the thumb and index finger during independent thumb and finger contractions in younger and older adults. In a second set of experiments, all subjects will perform a pinching force-accuracy task and the degree of synchronization and coherence between the thumb and index finger in younger and older adults will be compared with cross correlation analysis. Twenty older adults will be divided into two groups which will undergo different training programs for four weeks. One group will perform a take-home resistance training program and a matched group will perform a precision motor learning program. The incidence of self-sustained firing in single motor units and motor unit firing rate synchronization and coherence during pinching will be measured again post training. This elucidation of the neuromuscular mechanisms that enable hand steadiness will provide the foundation for the design of advanced rehabilitation systems.