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首页> 外文期刊>Journal of Neurophysiology >Motor control of low-threshold motor units in the human trapezius muscle.
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Motor control of low-threshold motor units in the human trapezius muscle.

机译：人体斜方肌中低阈值运动单位的运动控制。

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The firing pattern of low-threshold motor units was examined in the human trapezius and first dorsal interosseous (FDI) muscles during slowly augmenting, low-amplitude contractions that were intended to mimic contractile activity in postural muscles. The motor unit activity was detected with a special needle electrode and was analyzed with the assistance of computer algorithms. The surface electromyographic (EMG) signal was recorded. Its root-mean-square (RMS) value was calculated and presented to the subject who used it to regulate the muscle force level. In the trapezius, there was minimal, if any, firing rate modulation of early recruited motor units during slow contractions (< or =1% EMG(max)/s), and later recruited motor units consistently presented higher peak firing rates. As the force rate of the contraction increased (3% EMG(max)/s), the firing rates of the motor units in the trapezius approached an orderly hierarchical pattern with the earliest recruited motor units having the greatest firing rate. In contrast, and as reported previously, the firing rates of all motor units in the FDI always presented the previously reported hierarchical "onion-skin" pattern. We conclude that the low-threshold motor units in the postural trapezius muscle, that is the motor units that are most often called on to activate the muscle in postural activities, have different control features in slow and fast contractions. More detailed analysis revealed that, in the low force-rate contractions of the trapezius, recruitment of new motor units inhibited the firing rate of active motor units, providing an explanation for the depressed firing rate of the low-threshold motor units. We speculate that Renshaw cell inhibition contributes to the observed deviation of the low-threshold motor units from the hierarchical onion-skin pattern.
机译：在人斜方肌和第一背骨间（FDI）肌肉中，缓慢模仿低姿势运动的射击模式，旨在缓慢模拟姿势肌肉的收缩活动。用特殊的针状电极检测运动单位的活动，并借助计算机算法进行分析。记录表面肌电图（EMG）信号。计算其均方根（RMS）值并将其呈现给使用它来调节肌肉力量水平的受试者。在斜方肌中，早期收缩缓慢收缩（<或= 1％EMG（max）/ s）时，早期募集的运动单位的点火速率调制极少，如果有的话，后来募集的运动单位始终呈现较高的峰值点火速率。随着收缩力的增加（3％EMG（max）/ s），斜方肌运动单位的发动率接近有序的分层模式，最早募集的运动单位发动率最高。相反，如前所述，FDI中所有电机单元的点火率始终呈现先前报告的分层“洋葱皮”模式。我们得出的结论是，姿势斜方肌中的低阈值运动单位（即最常在姿势活动中被激活以激活肌肉的运动单位）在慢速和快速收缩中具有不同的控制功能。更详细的分析表明，在斜方肌的低力率收缩中，新电机单元的募集抑制了活动电机单元的点火率，从而为低阈值电机单元的点火率降低提供了解释。我们推测Renshaw细胞抑制作用有助于观察到的低阈值运动单位与洋葱皮样式的偏离。

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