Discharge frequency of the motor units in human muscles under different stationary isometric tension, investigated by a new method.

A new method has been worked out for selective recording of the impulses of individual MU under high muscular efforts. It is suggested to use the EMG derivatives (the differentiated EMG-DEMG and the double differentiated EMG-DDEMG and possibly the higher derivatives). It was demonstrated that at different stationary isometric tensions the dependence between the discharge frequency and the tension may be linear or non-linear, with a bigger growth at the small efforts and a smaller growth at the big efforts. The inverse non-linearity--sharp rise of the frequency at the high efforts--was not established. Conformation was found for the possibility of distinguishing between two types of MU according to the type of this dependence.