Abstract
The influence of starting positions of the arm on EMG-RTs of the biceps brachii muscle for elbow flexion and forearm supination was examined using 16 normal subjects. Two angles of the elbow joint, 45° and 110° flexion, and two positions of the forearm, 45° supination and 90° pronation, were used as the factorial combinations of all four. The EMG-RT for elbow flexion decreased in the order of 110° Pronation > 45° Pronation = 110° Supination > 45° Supination, and that for forearm supination decreased in the order of 45° Supination > 45° Pronation = 110° Supination > 110° Pronation. These results were kinesiologically interpreted that variations of EMG-RTs were based on the change in the number of synergic muscles participating in an intended movement and the muscle length of the prime mover at the start of the movement.
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