Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors.
Motor Unit Activity during Fatiguing Isometric Muscle Contraction in Hemispheric Stroke Survivors.
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DOI：
10.3389/fnhum.2017.00569
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发表时间：
2017
影响因子：
2.9
通讯作者：
Lowery MM
中科院分区：
文献类型：
--
作者：
McManus L;Hu X;Rymer WZ;Suresh NL;Lowery MM
中风后通常会出现肌无力增强，并可能伴有疲劳易感性增加。为了研究中枢和外周因素对中风幸存者等长肌疲劳的影响，本研究调查了运动单位（MU）平均放电率和动作电位时程在30%最大随意收缩（MVC）下持续次最大疲劳收缩期间和之后的变化。12名慢性中风幸存者在20%MVC疲劳前后进行了一系列第一背侧骨间肌的短收缩，并在10分钟恢复期后再次进行。使用表面EMG分解提取个体MU放电时间，并用于获得尖峰触发的平均MU动作电位波形。在持续疲劳收缩期间，所有检测到的MU的放电频率的平均变化率在受影响侧（-0.02 ± 0.03 Hz/s）大于受影响较少侧（-0.004 ± 0.003 Hz/s，p = 0.045）。疲劳后即刻，受累侧的击发频率变化也大于受累较少侧（-13.5 ± 20和0.1 ± 19%，p = 0.04）。恢复期后，与受累侧相比，受累较少侧的平均MU放电率增加（分别为19.3 ± 17和0.5 ± 20%，p = 0.03）。疲劳后两侧MU动作电位时程增加（受累侧为10.3 ± 1.2至11.2 ± 1.3 ms，受累较少侧为9.9 ± 1.7至11.2 ± 1.9 ms，分别为p = 0.001和p = 0.02），损伤程度越大，动作电位时程的变化越小（p = 0.04）。这项研究首次在卒中幸存者中提出了在等长疲劳收缩期间MU水平的中枢和外周疲劳的证据。总之，这些初步观察结果表明，对等长疲劳收缩的反应在中风后受影响的一侧和受影响较小的一侧之间是不同的，并且可能表明，在这里观察到的中枢机制作为放电率的变化是导致受影响一侧任务失败的主导过程。
Enhanced muscle weakness is commonly experienced following stroke and may be accompanied by increased susceptibility to fatigue. To examine the contributions of central and peripheral factors to isometric muscle fatigue in stroke survivors, this study investigates changes in motor unit (MU) mean firing rate, and action potential duration during, and directly following, a sustained submaximal fatiguing contraction at 30% maximum voluntary contraction (MVC). A series of short contractions of the first dorsal interosseous muscle were performed pre- and post-fatigue at 20% MVC, and again following a 10-min recovery period, by 12 chronic stroke survivors. Individual MU firing times were extracted using surface EMG decomposition and used to obtain the spike-triggered average MU action potential waveforms. During the sustained fatiguing contraction, the mean rate of change in firing rate across all detected MUs was greater on the affected side (-0.02 ± 0.03 Hz/s) than on the less-affected side (-0.004 ± 0.003 Hz/s, p = 0.045). The change in firing rate immediately post-fatigue was also greater on the affected side than less-affected side (-13.5 ± 20 and 0.1 ± 19%, p = 0.04). Mean MU firing rates increased following the recovery period on the less-affected side when compared to the affected side (19.3 ± 17 and 0.5 ± 20%, respectively, p = 0.03). MU action potential duration increased post-fatigue on both sides (10.3 ± 1.2 to 11.2 ± 1.3 ms on the affected side and 9.9 ± 1.7 to 11.2 ± 1.9 ms on the less-affected side, p = 0.001 and p = 0.02, respectively), and changes in action potential duration tended to be smaller in subjects with greater impairment (p = 0.04). This study presents evidence of both central and peripheral fatigue at the MU level during isometric fatiguing contraction for the first time in stroke survivors. Together, these preliminary observations indicate that the response to an isometric fatiguing contraction differs between the affected and less-affected side post-stroke, and may suggest that central mechanisms observed here as changes in firing rate are the dominant processes leading to task failure on the affected side.
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DOI：
10.1016/j.apmr.2015.06.009
发表时间：
2015-10-01
影响因子：
4.3
作者：
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