Electrophysiological Studies of the Biceps Brachii Activities in Supination and Flexion of the Elbow Joint

NAITO, A., YAJIMA, M., FUKAMACHI, H., USHIKOSHI, K., HANDA, Y., HOSHIMIYA, N. and SHMIZU, Y. Electrophysiological Studies of the Biceps Brachii Activities in Supination and Flexion of the Elbow Joint. Tohoku J. Exp. Med., 1994, 173 (2), 259-267-Activities of the biceps brachii (long head: BiL, short head: BiS) on the elbow joint were studied using an electrical neuromuscular stimulation (ENS) and an electromyography (EMG). In ENS study, ENS to BiL or BiS was performed in seven volunteers. Before ENS, the volunteer relaxed the upper extremity on a table with the elbow extended and the forearm pronated. Then ENS-induced movements of the upper extremity were examined. Movements of elbow flexion and forearm supination were induced simultaneously by ENS to BiS in all volunteer and by ENS to BiL in six volunteers. ENS to BiL of one volunteer resulted in only elbow flexion. In EMG study, averaged EMGs of BiL and BiS during a to-and-fro motion from prone to supine of the forearm with holding a load were analyzed in eight volunteers. The volunteer acted the movements with keeping the elbow joint in different angles. Although an increase and a decrease of EMG activities in BiL and BiS were observed accompanied by the degree of forearm supination, patterns of changes in quantities of EMG activities to changing elbow angles varied from individual to individual. These findings seem to indicate that each human subject has an individual use of the biceps brachii for supination movements, while the action of the muscle on the elbow joint is similar among the subjects.