Abstract

The purpose of the present study is threefold: first, to observe simultaneously the changes in both the frequency of motor unit (MU) discharges and the amplitude of surface electromyogram (EMG) during the prolonged and sustained voluntary efforts; and second, to demonstrate the effects of arterial occlusion the frequency of MU discharges; lastly, to discuss the mechanism of motor control in the light of the present results and others. Two male adults participated in the experiment. The following results were obtained. 1. The patterns of changes in the frequency of discharges of MUs were diveded into three types. The first pattern showed the steep decrease in the frequency of discharge of short period, and at last the discharge disappeared, the second the gradual prolongation of discharge intervals and the increase in both irregular fluctuation and slow undulation, the third constant frequency of discharge even immediately before the exhaustion of voluntary effort. 2. The undulation and prolongation of discharge intervals appeared during the abolition of blood supply to the arm. 3. The gradual increase in the amplitude of direct EMG in muscles biceps brachii was observed during holding a weight of constant load. Verf.-Referat (gekuerzt)