LARYNGEAL GESTURES AND ELECTROMYOGRAPHIC BEHAVIOR DURING BRACHIATION IN HUMAN

Occurrence of the laryngeal constriction, i. e. air trapping, which is thought to stabilize the thorax to assist the upper limb movements, were investigated in behaving human subjects by means of endoscopic and EMG recordings. Subjects employed in the experiments were 4 Japanese sports men; a Judo player, a Kendo player and two gymnasts. In two gymnasts; one won a silver medal at the 1984 Los Angeles Olympic, and the other one held the All Japan Gymnastics Championship (horizontal bar) title for five consecutive years. They were asked to perform brachiation. Laryngeal dynamic gestures were recorded by means of a specially designed endoscopic video system. EMGs were recorded for 8 muscles of the upper extremity and shoulder girdle using surface electrodes. Side view motion pictures of the behaving subjects were recorded by a video camera. Signals of the video frame (laryngeal gestures and motion pictures) were simultaneously recorded with the EMGs. During brachiation, the strong laryngeal sphincteric actions were consistently recognized in the case of Judo and Kendo players. However, in the case of two gymnasts, very little laryngeal closure was hardly observed throughout brachiation. In the case of Judo and Kendo players, the discharges of anterior portion of the deltoid and sternal and costal portion of the pectoralis major appeared and remarkably increased during swing phase with right arm. The laryngeal sphincteric actions were recognized at the period of increasing phase of these discharges which act for the adduction of the humerus. While, in the case of two gymnasts, the discharges of these muscles were hardly observed during swing phase with right arm. From these results, it has been strongly suggested that the laryngeal sphincteric actions are required to assist the adduction of the humerus in compensating for the increased load imposed on the shoulder joint.