Abstract
In order to compare mechanical measurements obtained with force platforms, film analysis
and a kinematic arm, a sprint runner and a long distance runner were asked to run
at different constant velocities ranging from 2.5 m · s-1 to 5.5 m · s-1. The external (EW) mechanical work reflected in the motion of the center of mass
(CM) of the subject was computed 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 force platforms). These differences
could be explained by (i) film analysis inaccuracy and (ii) vertical kinematic arm
oscillations. Furthermore, the data obtained with a multisegment model confirm that
the large discrepancy found in the literature on running efficiency is not mainly
due to the accuracy of the force and/or displacement measurements, but to the different
methods of estimation of the mechanical power produced by the muscles. It is suggested
that the kinematic arm principle can be applied successfully for computation of CM
displacements and CM energy changes during running.
Key words
Force plate - film analysis - kinematic arm - center of mass model - multi-segment
model - running
