FORWARD DYNAMICS FOR THE EVALUATION OF PRACTICAL PROBLEMS IN SPORTS

Abstract

INTRODUCTION: In athletic movements there are often situations where one cannot rate varying executions, because the effects of single actions are unknown. At a tennis stroke for example, the movement of the ball after hitting is well visible as an effect of the action. However, the conditions at hitting the ball and the actions that lead to the torque of hitting are not reliably visible. Their interpretation is only subjective. Nevertheless, the trainer and the player have to give statements of the muscular activity like "hold the racket loosely or firmly "or"relax or stiffen your wrist." This paper focuses on a controversial problem: the use of the wrist in tennis. Some favor a firm wrist, others an actively moving wrist. The group which favors the active wrist based their idea on the higher velocities of the racket head. For this idea biomechanical considerations are only based on kinematic data and on analysis in muscular physiology (see KLEINÖDER 1997, ELLIOT 1991, HUIJING 1994, KOMI 1994) and not on kinetic analysis. With this work we try to fill these gaps with computer simulation. In a similar way we worked on a problem in gymnastics: the increase of swings on the horizontal bar, which is necessary for all swing elements. Little work has been done in this area (see BAUER 1976, BÖHM1997 and WIEMANN 1993). Nevertheless, the research that allows a development of a general theory of the swing increase is lacking (except for the efforts of WIEMANN). The goal of this paper is to show that computer simulation can be a first step towards the development of such a theory.