Riley N A, Bilodeau M
Physical Therapy and Rehabilitation Science, College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
Disabil Rehabil. 2002 Dec 15;24(18):961-9. doi: 10.1080/0963828021000007932.
Little is known concerning changes in neuromuscular fatigue following a stroke. The purpose of this study was to evaluate the effect of a stroke on fatigue-related changes in upper limb torque patterns and electromyographic signals.
The paretic and non-paretic upper limb of 10 adults (51-79 years) who had a stroke (time since stroke: 3-75 months) were compared. Subjects had to perform a fatigue task consisting of a sustained maximal isometric contraction in elbow flexion until torque decreased to below 50% of initial. The main variables of interest assessed before, during and after fatigue were: (1) the torque in elbow flexion, as well as associated forces/torques at the shoulder and forearm; (2) the level of voluntary activation; (3) the amplitude (RMS); and (4) frequency content (median frequency) of electromyographic signals.
Compared to the non-paretic side, the paretic side showed a lower level of voluntary activation and higher relative torque levels at the forearm and shoulder which could both be exaggerated with fatigue, and a lesser fatigue-related decrease in median frequency.
Thus, greater fatigue-related changes in features of the central command (ability to maximally activate a muscle and ability to isolate effort to a muscle group) were observed for the paretic compared with the non-paretic side. This could be a confounding factor when assessing changes in peripheral measures of fatigue following a stroke using voluntary contractions.
关于中风后神经肌肉疲劳的变化，人们了解甚少。本研究的目的是评估中风对上肢扭矩模式和肌电信号中与疲劳相关变化的影响。
比较了10名中风成年人（51 - 79岁，中风后时间：3 - 75个月）的患侧和非患侧上肢。受试者必须执行一项疲劳任务，包括在肘部屈曲时持续进行最大等长收缩，直到扭矩降至初始值的50%以下。在疲劳前、期间和之后评估的主要感兴趣变量为：（1）肘部屈曲扭矩，以及肩部和前臂的相关力/扭矩；（2）自主激活水平；（3）肌电信号的幅度（均方根值）；（4）频率成分（中位频率）。
与非患侧相比，患侧的自主激活水平较低，前臂和肩部的相对扭矩水平较高，且两者都会因疲劳而加剧，并且与疲劳相关的中位频率下降较小。
因此，与非患侧相比，患侧在中枢指令特征（最大程度激活肌肉的能力以及将力量集中于一组肌肉的能力）方面观察到更大的与疲劳相关的变化。在使用自主收缩评估中风后外周疲劳指标变化时，这可能是一个混杂因素。
