Zhou Ping, Suresh Nina L, Rymer William Z
Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA.
Ann Biomed Eng. 2007 Sep;35(9):1521-31. doi: 10.1007/s10439-007-9329-3. Epub 2007 May 26.
The sensitivity of the electromyogram (EMG)-force relation to changes in motoneuron and muscle properties was explored using a simulation approach, and by applying existing motoneuron pool, muscle force, and surface EMG models. The simulation results indicate that several factors contribute potently to known changes in the EMG-force relation in paretic stroke muscles. First, compression of the motor unit recruitment range with respect to the injected current tends to generate greater EMG amplitude at a given force, and to produce a highly nonlinear EMG-force relation. The overall mean slope of the EMG-force relation tends to be flatter, primarily because of this non-linear behavior. Second, with reductions of the mean motor unit firing rates, the slope of the EMG-force relation also tends to increase especially as the mean firing rates dropped substantially below the motor unit fusion frequency. Finally, similar effects were observed with a reduction in the number of motor units, and with variation in motor unit contractile properties, which also altered the EMG-force relation. These findings provide new insight toward our understanding of experimental EMG-force relations in both normal and pathological states, such as the abnormal EMG-force relations of paresis muscles in stroke.
利用模拟方法，并通过应用现有的运动神经元池、肌肉力量和表面肌电图模型，探讨了肌电图（EMG）-力量关系对运动神经元和肌肉特性变化的敏感性。模拟结果表明，有几个因素对中风偏瘫肌肉中已知的EMG-力量关系变化有显著影响。首先，相对于注入电流，运动单位募集范围的压缩往往会在给定力量下产生更大的EMG幅度，并产生高度非线性的EMG-力量关系。EMG-力量关系的总体平均斜率往往更平缓，主要是由于这种非线性行为。其次，随着运动单位平均放电率的降低，EMG-力量关系的斜率也往往增加，尤其是当平均放电率大幅低于运动单位融合频率时。最后，在运动单位数量减少以及运动单位收缩特性变化时也观察到了类似的效应，这也改变了EMG-力量关系。这些发现为我们理解正常和病理状态下的实验性EMG-力量关系提供了新的见解，例如中风中偏瘫肌肉的异常EMG-力量关系。
