Pulse Control during Rapid Isometric Contractions of the Elbow Joint

正常被试在不同振幅目标下以快速收缩速率施加等距扭矩，在恒定目标下以不同速率施加等距扭矩。在最快的收缩中，激动剂肱三头肌和拮抗剂肱二头肌表现出以慢波为特征的肌电截击，初始为负相，随后为正相。在不同的靶振幅下，各相持续时间相对恒定。在激动剂中，由负或正波形组成的面积随着目标振幅的增加而增加，并与扭矩一阶导数的峰值相关。拮抗剂齐射与靶波幅的关系在区域和间隔上都存在差异。随着收缩速率的降低，在与扭矩导数峰值相关的区域，激动剂截击减少，持续时间保持恒定，而拮抗剂截击消失。这些结果表明，快速等距收缩是由激动剂激活的振幅调制脉冲控制的，而激动剂激活的脉冲与拮抗剂激活的脉冲相关，而拮抗剂激活的脉冲在不同的受试者中被不同地利用。

Normal subjects exerted isometric torque at a rapid rate of contraction with different amplitude targets, and at different rates with a constant target. In the fastest contractions, the agonist triceps and antagonist biceps muscles showed an electromyographic volley characterized by a slow wave with an initial negative and subsequent positive phases. The duration of each phase was relatively constant for different target amplitudes. In the agonist, the area comprised by the negative or positive waveform increased with increasing target amplitude and correlated with the peak of the first time derivative of torque. The relationship of the antagonist volley to the target amplitude varied among subjects both in the area and the interval of the agonist-antagonist volley. With a decreasing contraction rate, the agonist volley decreased in the area in correlation with the peak of the torque derivative, retaining a constant duration, while the antagonist volley disappeared. These results suggest that rapid isometric contractions are controlled by an amplitude-modulated pulse of agonist activation, which is associated with a pulse of antagonist activation, while the pulse of the antagonist activation is variably utilized among subjects.