TONIC AND KINETIC COMPONENTS OF THE EVOKED ELECTROMYOGRAM

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Abstract
The peak-to-peak amplitude of the H-wave of the gastrocnemius muscle was inhibited in inspiration, in lying on the recorded side and in an ankle extension, while the magnitude of the mechanical response was augmented. The form of H-wave is not tetra-phasic, but is very often superimposed by a small notch suggesting that the H-wave is composed of 2 components. The long latency component has a lower threshold to stimulation of the dorsal root filament and potentiated by tetanic stimulation. The short latency component has a lower threshold to stimulation of the ventral root filament and augmented during voluntary contraction. Some muscular units have the same latency with the H-wave and others fire coincident with the appearance of the notch. The short and long latency component is the kinetic and tonic activities, respectively. The H-wave is the vector summation of these 2 activities, so that the peak-to-peak amplitude can not be a measure of the mechanical response. H-waves in various state of muscular activities were discussed from the standpoint of tonic and kinetic activities.