Abstract

In normal subjects, the premotor time and electromyographic reaction time (EMG-RT) of the biceps brachii has been determined to be different in flexion (F) and supination (S) of the forearms. Accordingly, while the same muscle performs in both functions, these two voluntary movements would be separately organized in the brain. Moreover, the EMG-RT differences, obtained by subtracting the EMG-RTs of S from those of F, disappeared in athletes of unilateral sporting events (Kasai, 1982; 1983). The present experiments are therefore undertaken to examine the effects of forehand and backhand stroke practice by the preferred hand on the EMG-RTs of F and S, and to collect information with respect to the practice influences on the motor control systems in the brain. The findings are interpreted as follows: First, the motor pattern generator would be influenced by unilateral forehand and backhand stroke practices. Moreover, the difference of the practice task (movement pattern) plays an important role in different functional changes of the motor pattern generator: Second, the period of continuation of the practice plays an important role in changes of the quality of a system programming the movement patterns (the motor control systems). From these interpretations, it is suggested that the quality of movement patterns in each sports activity should be analysed to investigate the mechanisms of motor learning. Verf.-Referat