Abstract

The influence of starting positions of the forearm on premotor reaction times (PMTs) of the biceps brachii muscle for elbow flexion was examined in 13 normal subjects. Two angles of the elbow joints, 0 and 90 degrees, and two positions of the forearm, supination (s) and pronation (P), were examined as the factorial combinations of all four. The PMT of starting from S for elbow flexion was significantly shorter than that of P at both elbow angles. The PMT of 90 degrees flexion of elbow angle was shorter than that of 0 degree in both forearm positions but differences between them were not statistically significant. These results support the previous study by TANIGUCHI, NAKAMURA and KASAI (1984). EMG onsets of four muscles (biceps, triceps, forearm flexor and forearm extensor) were significantly different among varying starting positions; that is, the EMG onsets in P were simultaneous but separate in S. These results have lprovided new kinesiological evidence to the above-mentioned report the interpretion being that variations of PMTs in varying initial positions of the forearm for elbow flexion are based on the change, not only in the numbe rof synergic muscles participating, but also in the timing of synergistic muscles participating in an intended movement. Verf.-Referat