THE ROTATIONAL ABILITY OF 'THE HUMAN BODY
AbstractIn sports like gymnastics, trampolining and diving, attention is focussed on control and good execution. Like all general movements, the movements involved in such sports are motions that consist of translation and rotation. However in this case, proficiency depends dominantly on the rotational ability of the athlete while performing the movement. We analyze such a movement using parameters from anthropometry, dynamics, and posture. We recorded anthropometric data of top athletes in trampolining and compared them with those of ordinary people. With a computer program based on the Hanavan model together with mass density values given by Dempster, we use the data to calculate the inertia tensor. Further data pertaining to dynamics, timing and coordination are derived by video-cinematographic methods. With the aid of two cameras, we filmed simultaneously various trampoline performances during the international competition held in Dillenburg, Germany in 1991. The videos were then digitized and the data processed by computer. We obtain the results for momentum, body orientation, posture and the center of gravity of the trampolinists during a jump. We demonstrate how strongly body structure, dynamics, timing and coordination contribute to the ability of the human body to rotate. The important parameters are the inertia tensor and the momentum, the combination of which determines the rotating. While momentum remains constant during a jump, the inertia tensor may vary in time due to different postures. Our findings show what momentum is necessary and which posture have to be in sequence for athletes to excel.