MECHANICAL ENERGY ASSESSMENT WITH DIFFERENT METHODS DURING RUNNING

In order to compare mechanical measurements obtained with force platfo rms, film analysis and a kinematic arm, a sprint runner and a long dis tance runner were asked to run at different constant velocities rangin g from 2.5 m . s-1 to 5.5 m . s-1. The external (EW) mechanical work r eflected in the motion of the center of mass (CM) of the subject was c omputed using force platforms, film analysis and a kinematic arm. The differences observed on EW computations ranged from 12.3 % +/- 2.5 % ( film analysis vs kinematic arm) to 1.4 % +/- 1.8 % (kinematic arm vs f orce platforms). These differences could be explained by (i) film anal ysis inaccuracy and (ii) vertical kinematic arm oscillations. Furtherm ore, the data obtained with a multisegment model confirm that the larg e discrepancy found in the literature on running efficiency is not mai nly due to the accuracy of the force and/or displacement measurements, but to the different methods of estimation of the mechanical power pr oduced by the muscles. It is suggested that the kinematic arm principl e can be applied successfully for computation of CM displacements and CM energy changes during running.