Changes in motor unit behavior following isometric fatigue of the first dorsal interosseous muscle
Changes in motor unit behavior following isometric fatigue of the first dorsal interosseous muscle
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DOI：
10.1152/jn.00146.2015
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发表时间：
2015-05-01
影响因子：
2.5
通讯作者：
Suresh, Nina L.
中科院分区：
文献类型：
--
作者：
McManus, Lara;Hu, Xiaogang;Suresh, Nina L.
用来补偿疲劳引起的肌肉力量缺陷的神经肌肉策略还不清楚。本研究利用表面肌电信号(SEMG)结合个体运动单位动作电位(MUAP)的记录，研究持续疲劳收缩后即刻和恢复期后运动单位(MU)行为的潜在代偿性改变。在12名受试者的第一背侧骨间外展期间，在20%的最大自愿收缩(MVC)下，在30%的MVC疲劳收缩到任务失败之前和之后立即记录EMG活动，并在休息10min后再记录20%的MVC收缩。分析由表面肌电信号分解系统提取的MUAP的波幅、时程和平均放电频率(MFR)以及表面肌电信号的均方根(RMS)波幅和中值频率(MPF)。MUAP持续时间和波幅在疲劳后即刻增加，并分别与sEMG、MPF和RMS的变化相关。10min后，MUAP时程和肌电MPF恢复至疲劳前水平，但MUAP波幅和肌电均方根仍高于疲劳前。MU、MFR和招募阈值在疲劳后降低，休息后恢复。MUAP和sEMG波幅的增加可能反映了较大的MU的招募，而招募压缩是疲劳后直接的一种额外的补偿策略。MU MFR的恢复与MUAP持续时间平行，提示代谢敏感传入可能在疲劳后MFR抑郁中起作用。这项研究通过检测大量同时记录的单个MU的特性来洞察疲劳诱导的神经肌肉变化，并概述了涉及MU招募和MFR改变的可能的代偿策略。
The neuromuscular strategies employed to compensate for fatigue-induced muscle force deficits are not clearly understood. This study utilizes surface electromyography (sEMG) together with recordings of a population of individual motor unit action potentials (MUAPs) to investigate potential compensatory alterations in motor unit (MU) behavior immediately following a sustained fatiguing contraction and after a recovery period. EMG activity was recorded during abduction of the first dorsal interosseous in 12 subjects at 20% maximum voluntary contraction (MVC), before and directly after a 30% MVC fatiguing contraction to task failure, with additional 20% MVC contractions following a 10-min rest. The amplitude, duration and mean firing rate (MFR) of MUAPs extracted with a sEMG decomposition system were analyzed, together with sEMG root-mean-square (RMS) amplitude and median frequency (MPF). MUAP duration and amplitude increased immediately postfatigue and were correlated with changes to sEMG MPF and RMS, respectively. After 10 min, MUAP duration and sEMG MPF recovered to prefatigue values but MUAP amplitude and sEMG RMS remained elevated. MU MFR and recruitment thresholds decreased postfatigue and recovered following rest. The increase in MUAP and sEMG amplitude likely reflects recruitment of larger MUs, while recruitment compression is an additional compensatory strategy directly postfatigue. Recovery of MU MFR in parallel with MUAP duration suggests a possible role for metabolically sensitive afferents in MFR depression postfatigue. This study provides insight into fatigue-induced neuromuscular changes by examining the properties of a large population of concurrently recorded single MUs and outlines possible compensatory strategies involving alterations in MU recruitment and MFR.