Analysis of Release Technique of Japanese-style Bow by Using Electromyogram

Abstract

Since the Japanese-style bow is very complicated in shape and structure, torques in horizontal and sagittal planes about the grip must be applied to hit the target. The purpose of this study was to investigate the relationship between left forearm muscle activities and torques in horizontal and sagittal planes about the grip. Surface EMGs of four muscles (extensor carpi radialis longus, extensor digitorum, extensor carpi ulnaris, flexor carpi ulnaris) and torques were collected for ten male subjects shooting arrows. Crosstalks between EMGs obtained from adjacent recording muscles were evaluated by using cross-correlation function. Absolute values of less than 0.3 of cross-correlation coefficient were considered as a criterion for specific EMG signals. As a result of statistic analysis. Extensor digitorum and extensor carpi ulnaris muscles had positive relationships to the torque in the horizontal plane. On the other hand, extensor carpi ulnaris, flexor carpi ulnaris and flexor carpi ulnaris muscles had positive relationships to the torque in the sagittal plane. It is found that extensor carpi ulnaris is a bifunctional muscle in release technique (TENOUCHI) of Japanese-style bow.