The relationship between barbell velocity and ground reaction force of athlete-device system during the snatch

The best evaluation of usefulness of particular exercises in the process of movement technique perfectioning is the knowledge about its internal and external structure. It needs a complex methodology of research (Nawrat, Król 1989). The simultaneous use of many devices registering the flow of different kinematic or dynamic variables is very often impossible when the movements are performed at large spaces, are relatively fast or three-dimensional. The necessity of resigning from the simultaneous measuring of dynamics as well as kinematics of movement is undoubtedly a simplification, because in this situation the conclusions are based on incomplete information. The situation seems to be a little better because of fact, that some relationships between particular variables may be observed. In case of the snatch – in weightlifting – such a relationship was determined between barbell velocity and the change of angle called “knee bend” (Król 1993). Similarly it may be done in relation to other variables describing the movement. During weight lifting the barbell and weightlifter constitute a bio-kinematic chain, in which movements of particular elements interact with each other. It was then assumed, that during the snatch in the athlete-device system a relationship exists between maximum vertical velocity of the barbell1
and ground reaction force (GRF).