Motor Unit Activity and Force Steadiness Changes w Aging

描述（由申请人提供）： 神经肌肉系统在衰老过程中经历显著的去神经支配和肌肉萎缩。肌肉力量的产生变得不那么稳定，特别是在肌肉力量的控制释放和低力收缩期间。失去对手灵活性的控制对许多老年人的生活质量和那些受肌肉骨骼疾病废用性萎缩影响的人是极其有害的。本研究将探讨老化过程中手部稳定性下降的可能机制。 我们假设，有一个较高的发生率，自我持续射击运动神经元的老年人，这种行为有助于增加难以顺利释放肌肉力量。其次，我们假设老年人拇指和食指肌肉的运动单位同步性和一致性增加，这可以解释在功能性手部任务（如捏）中观察到的稳定性下降。最后，我们将确定运动单位放电频率同步性和拇指和食指一致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。 这项研究将包括两组实验之前和之后进行一个月的培训计划。第一个将调查单一的运动单位发射率和自我持续发射的肌肉服务的拇指和食指在独立的拇指和手指收缩在年轻人和老年人的发病率。在第二组实验中，所有受试者将执行捏力准确性任务，并将用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。一组将执行带回家的阻力训练计划，一个匹配的组将执行精确的运动学习计划。在训练后将再次测量单个运动单元中的自我维持放电的发生率以及捏夹期间运动单元放电率同步性和连贯性。这种阐明的神经肌肉机制，使手稳定将提供先进的康复系统的设计基础。

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.