Determination of age- and sex-related differences in motor unit activity

肌肉活动传统上是在实验室研究中测量的，结果随后被推断为在日常生活中提供功能下降的指示。然而，我的实验室最近的工作是第一个使用便携式肌电图（EMG）来测量日常生活中的肌肉活动。每天8小时的上肢和下肢肌肉记录表明，与男性相比，女性的低阈值肌电图增加，而且这种差异随着年龄的增长而增大。低阈肌电图通过评估肌肉活动爆发（>0 %最大自愿收缩（MVC）， >0.1s持续时间）和活动间隙（<最大>0.1s持续时间的1%）来量化。低阈值肌电图中与性别和年龄相关的增加的潜在原因仍有待确定。表面肌电记录只检测到电极记录区域内活动的运动单元（MU）肌肉纤维的活动。因此，我的研究的直接目的是确定MU招募和出院率的变化是否有助于低阈值肌电图的年龄和性别相关的增加。我的工作假设是，由于运动过程中肌肉长度的变化，运动神经元池的感觉反馈被改变，MU的招募和放电速率被调节，这影响了低阈值肌电图记录。老年人和女性较短的肌束长度和较大的肌腱顺应性会影响体位依赖效应。这些研究将有助于理解感觉反馈在调节MU活动中的基本生理作用，并阐明与年龄和性别相关的低阈值肌电活动增加的原因。

Muscle activity has traditionally been measured in laboratory studies, and results have subsequently been extrapolated to provide an indication of functional decline during daily life. However, recent work in my laboratory is the first to use portable electromyography (EMG) to measure muscle activity during daily life. These recordings over a typical 8-hour day in upper and lower limb muscles indicate that low threshold EMG increases in women compared with men, and that this difference becomes greater with age. Low-threshold EMG is quantified through assessing bursts of muscle activity (>2% maximum voluntary contraction (MVC), >0.1s duration) and gaps in activity (<1% of maximal >0.1s duration). The underlying cause of sex- and age-related increases in low threshold EMG remains to be determined. Surface EMG recordings detect only activity from muscle fibres of motor units (MU) active within the recording area of the electrode. Thus, the IMMEDIATE OBJECTIVE of my research is to determine whether changes in MU recruitment and discharge rates contribute to the age- and sex-related increase in low threshold EMG. My WORKING HYPOTHESIS is that as a consequence of changes in muscle length during movement sensory feedback to the motor neuron pool is altered and MU recruitment and discharge rates are modulated and this influences the low-threshold EMG recordings. Shorter muscle fascicle length and greater tendon compliance in old adults and women will influence the position dependent effect. These studies will contribute to understanding the basic physiological role of sensory feedback in modulating MU activity and elucidate the cause of age- and sex-related increases in low threshold EMG activity.