Lukács Miklós, Vécsei László, Beniczky Sándor
Department of Neurology, University of Szeged, Semmelweis u. 6, H-6725, Szeged, Hungary.
Muscle Nerve. 2009 Jul;40(1):112-4. doi: 10.1002/mus.21241.
Motor units (MUs) are recruited according to the size principle. At low force output, macro-motor unit potentials (macro-MUPs) with small amplitude and area are recorded; MUs with large electrical size fire at high force output. Our objective was to elucidate whether this difference is caused by a higher fiber density (FD) of the MUs recruited at high force output. We measured the FD and respectively the amplitude and the area of the macro-MUPs via single-fiber macro electromyography (EMG) recorded at low and high force output in 48 healthy subjects. The macro-MUPs were significantly larger at high force output than at low force. The FD did not differ at the two force levels. Our findings suggest that the larger electrical size of the high recruitment threshold MUs is due not to a higher FD, but to a larger territory. FD is a robust EMG parameter, independent of the level of the force output.
运动单位（MUs）是根据大小原则进行募集的。在低力输出时，记录到的是振幅和面积较小的大运动单位电位（macro-MUPs）；而电尺寸较大的运动单位在高力输出时放电。我们的目的是阐明这种差异是否由高力输出时募集的运动单位具有更高的纤维密度（FD）所致。我们通过单纤维宏肌电图（EMG）测量了48名健康受试者在低力输出和高力输出时的FD以及macro-MUPs的振幅和面积。高力输出时的macro-MUPs明显大于低力输出时的。在两个力水平下，FD没有差异。我们的研究结果表明，高募集阈值运动单位较大的电尺寸并非由于更高的FD，而是由于更大的范围。FD是一个稳健的肌电图参数，与力输出水平无关。
