Mechanism of rate cording and recruitment in motor units of lower extremity muscle during walking in human

本研究的目的是阐明青年人和老年人在自由行走或不同速度行走时对下肢运动单位（LE）的募集和放电频率的控制。采用非线性系统分析软件MemCalc计算表面肌电信号的频率。结果表明：在自由步行周期中，站立早期下肢肌的肌电活动大于摆动期，这可能是由于自由步行过程中快肌纤维中较大的运动单位与慢肌纤维中较小的运动单位之间的募集速率相同，从而控制了站立早期下肢肌的肌电活动。VL在站立早期的较大肌电活动被显著控制，以募集快肌纤维中较大的运动单位，选择性地抑制慢肌纤维中较小的运动单位的募集。另一方面，肌电活动越大， ...更多信息 在站立早期，MH的活性被显著控制，以募集慢缩肌纤维中较小的运动单位，选择性地抑制快缩肌纤维中较大的运动单位的募集，MG在站立期持续激活，站立中期肌电活动最大，认为站立早期肌电活动较大，是为了募集快-慢动作时较大的运动单位。不同步速下各肌群的肌电活动特征趋于一致，老年人（65岁以上）的肌电活动大于青年人，而对照组各肌群的肌电活动则不同。提示老年人自由行走时TA控制在快肌纤维和慢肌纤维相同的募集速率。提示老年人的MG和MH是为了募集快缩肌纤维中较大的运动单位，而老年人的VL是为了选择性地募集慢缩肌纤维中较小的运动单位。自由行走时肌肉纤维会抽搐少

The purpose of this study was to clarify the control over recruitment and firing rate of motor units of lower extremity (LE) muscles during free or different walking speeds in young adult and elderly. The frequency obtained surface electromyography (EMG) was calculated by MemCalc which was nonlinear system software. The results were as followed.EMG activities of LE muscles during early stance phase were greater than those during swing phase in walking cycle.It was considered that the greater EMG activities of TA for early stance phase was controlled in the same rates of recruitment between the larger motor units in fast-twitch muscle fibers and smalier motor units in slow-twitch muscle fibers during free walking. The greater EMG activity of VL in early stance phase was significantly controlled to recruit the larger motor units in fast-twitch muscle fibers, inhibiting recruitment of the smaller motor units in slow-twitch muscle fibers selectively. On the other hand, the greater EMG acti … More vity of MH in early stance phase was significantly controlled to recruit the smaller motor units in slow-twitch muscle fibers, inhibiting recruitment of the larger motor units in fast-twitch muscle fibers selectively.The MG was constantly activated during stance phase, the activity in mid stance phase was greatest it was considered that the greater EMG activity of MG for early stance phase was controlled to recruit the larger motor units in fast-twitch muscle fibers, and this greater activity was important to transfer to push-off during stance phase.The characteristics of each muscle EMG activity tended to be similar in different walking speeds.The EMG activities in the elderly (over 65 years) were greater than those in young adult The controls were different in each muscle. It was suggested that the TA in the elderly was controlled in the same rates of recruitment between the fast-twitch muscle fibers and the slow-twitch muscle fibers during free walking.On the other hand, it was suggested that the MG and MH in the elderly were controlled to recruit the larger motor units in fast-twitch muscle fibers and the VL in the elderly was selectively controlled to recruit the smaller motor units in slow-twitch muscle fibers during free walking. Less