Abstract
The purpose of this study was to examine the muscle force control of elbow flexor muscles in relation to gradual increase and decrease of weights. Seven healthy male subjects participated in the study. While the elbow of the subjects was flexed at 90 degrees, weights were applied to the palmar surface and the position was maintained in an isometric fashion. The muscle activities of the biceps brachii muscle and brachioradial muscle were recorded while the weight was increased or decreased gradually. The results of the experiment showed a strong correlation between the muscle activities of both muscles and the weight. Two changing patterns were observed during the experiment in the activities of both muscles: reciprocation and complementation. These results reveal that the muscle activities of both muscles correspond to changes in weight. Furthermore, they suggest that, even in a single joint movement, the contraction pattern among synergistic muscles has compensation and degrees of freedom.
