The Effects of Elbow Joint Angle Change on the Elbow Flexor Muscle Activation in Pulley with Weight Exercise

[Purpose] This research investigated the effect of angular variation of flexion of the elbow joint on the muscle activation of elbow flexor muscles. [Subjects] The research subjects were 24 male college students with a dominant right hand who had no surgical or neurological disorders and gave their prior written consent to participation with full knowledge of the method and purpose of this study. [Methods] The subjects' shoulder joints stayed in the resting position, and the elbow joint was positioned at angles of 55 degrees, 70 degrees, and 90 degrees. The angle between the pulley with weights and forearm stayed at 90 degrees. Surface electromyography was used to measure muscle activities. Three measurements were made at each elbow angle, and every time the angle changed, two minutes rest was given. [Result] The muscle activities of the elbow flexors showed significant changes with change in the elbow joint angle, except for the biceps brachii activities between the angles of 55 degrees and 70 degrees of elbow flexion. The muscle activities of the biceps brachii and brachioradialis showed angle-related changes in the order of 55 degrees, which showed the biggest value, followed by 70 degrees and 90 degrees. [Conclusion] In order to improve muscle strength of the elbow flexor using a pulley system, it seems more effective to have a 90 degrees angle between the pulley with weights and the forearm when the muscle is stretched to a length 20% greater than its resting position.