Abstract des Autors

A study was undertaken to investigate whether the amplitudes of reflex EMG components (M 1, M 2 and M 3) induced by sudden muscle stretching in the wrist flexor, are modified according to the reaction movement during wrist flexion, and how the aspects of reflex EMG components are related to premotor time under conditions of stretch stimulus (SS-PMT) and light stimulus (LS-PMT). Fifteen healthy men, ranging in age from 22 to 28 yr, participated in the study. A DC torque motor was used to evoke the reflex EMG activities on the wrist flexor. Analysis of the surface electromyogram recorded from the wrist flexor showed that short and long latency reflex components appeared in response to muscle stretch. In almost all subjects, the amplitude of the M 2 component was higher during reaction task than during no reaction task. The subjects were classified into two groups (I, II) according to the presence or absence of reflex components and their EMG amplitudes. SS- and LS-PMTs in group I were significantly shorter than those in group II. The amplitude of M 2 in group I was significantly higher than in group II. In group I the M 3 component was not identified, since the M 2 component was followed by a voluntary EMG burst. These results showed that the amplitudes of long latency reflex components increased during the reaction task in the flexion direction, and suggest that long latency components contribute to the initiation of voluntary movement in subjects with a shorter premotor time. Verf.-Referat