Optimisation of performance in running jumps
Running jumps such as the high jump and the long jump involve complex movements of the human body. The factors affecting performance include approach conditions, strength of the athlete and the muscle activation timings at each joint. In order to investigate the mechanics of jumping performances and the effect of these factors, an eight-segment, subject specific, torque-driven computer simulation model of running jumps was developed, evaluated and used to optimise performances of jumps for height and distance. Wobbling masses within the shank, thigh and trunk segments, and the ground-foot interface were modelled as non-linear spring-damper systems. The values for the stiffness and damping constants were determined through optimisation. The inertia data were obtained from anthropometric measurements on the subject using the inertia model of Yeadon (1990b). Joint torques predicted by the simulation model were expressed as a function of angular velocity and angle using data collected from an isovelocity dynamometer. The simulation model was evaluated by comparing the actual performances with simulations using kinematic and kinetic data collected. Movement of the wobbling masses was found to be in the region of 40 mm in the shank and thigh and 90 mm in the trunk. This movement resulted in a lower, more realistic initial peak in the ground reaction force. Co-contraction was found to occur at the joints during impact in order to increase the initial level of eccentric activation and also the rise time to maximum eccentric activation. Differences of 2% and 1% in the height and distance achieved were obtained between actual performances and simulations. An optimisation procedure was used to maximise the height reached and distance travelled by the mass centre, in simulations of jumps for height and distance respectively, by varying the torque generator activation time histories at each joint. An increase of 12% in the height reached by the mass centre in the jump for height and 14% in the distance reached by the mass centre in the jump for distance were achieved.