Analysis of motor skills for throwing darts: Measurement of release timing

Recently, measurement, analysis, and modeling of human motor functions have been intensively studied, because motor skills are useful for various applications, such as digital archiving, sports training, and rehabilitation. Targeting these practical applications, we focused on the throwing darts motion, which requires sophisticated control of the upper arm to realize precise throwing. In our previous research, we confirmed that both motion trajectories and muscle activities of experts become more stable during the throwing motion. However, we did not examine release timing, which is a significant factor for dart control. In this paper, we investigated the relationships among motion trajectories, muscle activities, and precision of the throwing darts motion from the viewpoint of release timing. To precisely measure release timing, we developed a measuring apparatus. Experimental results showed that skilled subjects demonstrated high stability of both motion trajectories and muscle activities, particularly before release timing. It was confirmed that the skilled subjects tried to reduce the degree of freedom of their upper arms to keep their throwing motion trajectories stable at this phase. In addition, it was suggested that the motion trajectory, release timing, and the muscle activity were optimized in this order as the throwing precision improved.