How the Body Shrink Influences Controllability of Skillful Movements

Abstract

In this paper, we investigate how the body shrink influences controllability of skillful movements in playing ball games as well as in playing the string instruments. Body shrink may be brought either by getting sudden muscle weakness or by overstraining. A typical defect caused by the body shrink is losing body control caused by loosening power delivery path like uncontrollable kites with sudden wind lost. This power delivery loosening in turn is brought by the body shrink. We give an explanation of this defect in terms of the whip dynamics in biomechanics. We point out the difficulty of discerning this uncontrollability because of the subtle feeling of the phenomena. An interactive interview is conducted to extract hidden points of interests among authors consisting of an amateur and professional cello players and two discussion mediators (facilitators). We found several related issues such as the importance of the bow holding by pinching and the relationship between taking the action-reaction law into account and avoiding the loosening of the power delivery path. These new points give hints how to avoid the problem discussed in this paper.