Evaluation of visual-motor coordination as a ball is caught

This study is based on an analysis of visual-motor coordination as a ball is caught. Humans obtain most of their information about the external environment from their sense of sight during daily life and sports activities. Sight enables us to judge the distance to objects and is important for controlling the musculoskeletal system and maintaining posture. Therefore, analyzing visual-motor coordination is essential for clarifying how humans relay visual information to their motor control system. This study analyzed the coordination between the lines of sight and upper limbs of receivers as they caught a ball with both hands, as a first step in the quantitative evaluation of visual-motor coordination. Singular value decomposition was applied to an observation matrix consisting of the upper limb joint angles and the pixel coordinates of the line-of-sight positions obtained in the experiment. We evaluated the cooperative relation between the lines of sight and the upper limbs by using the space basis vectors in the first and second modes, which had the highest contribution ratios. We compared the results for the condition in which a thrower tossed the ball after stating the direction in which the ball would be tossed. Furthermore, we also compared the results for the condition in which the thrower tossed the ball without stating the intended direction. The results demonstrated that the movements of specific joints were coordinated with changes in the lines of sight when the throwing direction was announced in advance. We therefore conclude that visual-motor coordination during daily life and sports activities can be clarified using the proposed method.