EVALUATION OF THE LOWER LIMBS MOTOR STRATEGIES DURING VERTICAL JUMPING

Abstract

Vertical jump is a test widely adopted by tainers to evaluate some motor characterisitcs of the athletes. The performance index usually measured, is the maximum vertical displacement of the centre of mass from its position when the athlete is standing. Aim of this paper is the study of the vertical jump through the variables related with the mechanical contribution of the muscular groups acting on the three main joints of the lower limb. Subjects of the study were 9 professional football players belonging to AC Milan football club. The players performed series of vertical jumps using either the thrust of both the legs, or the thrust of only one leg.The co-ordinates of five anatomical landmarks of the lower limb together with the ground reaction forces, were detected simultaneously by the ELITE System, with a sample frequency of 100 Hz. A specially designed software was implemented to compute the performance index ( differential height of the jump), the net joints' moments and the powers. The results show the following:-the performance index (average=539+-45mm)of the jumps performed with the thrust of both the legs, confirms the high athletic level of the players. -When the players jump with the thrust of one leg the performance index decreases significantly ( average=366+-44mm),-the maximal moments exerted bz the joints muscles when only one limb acts, are significatively greater than the correspondent values computed during the action of both the limbs. This difference almost disappears when the powers data are considered. This result is in relation with the different angular velocities of joints' extension. - even if vertical jump is a simple test easy to perform, especailly by people with high motor skills, it is possible to identify mechanical and moter asymetries between the same muscular groups of the two legs and between the motor patterns adopted by subjects characterised by the same performance index. The method seems to be useful to monitor the effect on the motor mechanisms due to specific training procedure and the motor recovery of the athlete after injuries.