ELECTROPHYSIOLOGICAL STUDIES OF THE BICEPS BRACHII ACTIVITIES IN SUPINATION AND FLEXION OF THE ELBOW JOINT

Activities of the biceps brachii (long head: BiL, short head: BiS) on the elbow joint were studied using an electrical neuromuscular stimula tion (ENS) and an electromyography (EMG). In ENS study, ENS to Bit or BiS was performed in seven volunteers. Before ENS, the volunteer relax ed the upper extremity on a table with the elbow extended and the fore arm pronated. Then ENS-induced movements of the upper extremity were e xamined. Movements of elbow flexion and forearm supination were induce d simultaneously by ENS to BiS in all volunteer and by ENS to Bit in s ix volunteers. ENS to Bit of one volunteer resulted in only elbow flex ion. In EMG study, averaged EMGs of Bit and BiS during a to-and-fro mo tion from prone to supine of the forearm with holding a load mere anal yzed in eight volunteers. The volunteer acted the movements with keepi ng the elbow joint in different angles. Although an increase and a dec rease of EMG activities in Bit and BiS were observed accompanied by th e degree of forearm supination, patterns of changes in quantities of E MG activities to changing elbow angles varied from individual to indiv idual. These findings seem to indicate that each human subject has an individual use of the biceps brachii for supination movements, while t he action of the muscle on the elbow joint is similar among the subjec ts.