Computation of the mechanical power of a manual wheelchair user in actual conditions: preliminary results

Ambulationwith amanual wheelchair (MWC) is considered as a strenuous form of locomotion both in terms of energetics and in terms of stresses of the musculo-skeletal system. Until now, energetic aspects were only investigated from metabolic measurements, which required the subject to continuously perform the task during several minutes in order to reach a stable metabolic state. Then, it is difficult and sometimes dangerous to study some tasks like starting, stopping or climbing a slope or a little threshold, for instance. So, studying the energetics in these tasks from a mechanical point of view should allow overcoming the limitations induced by the metabolic measurements. Power output during MWC propulsion was computed a long time ago, either from the power dissipated by the rolling resistance or from the power of the propelling torque measured with an instrumented wheel (van der Woude et al. 2001). However, these methods do not allow assessing the mechanical power really produced by the user, and a novel method was recently proposed (Sauret, Vaslin et al. 2012). This latter relies on classical mechanical principles and particularly on the theorem of the kinetic power focused on the {user} system. Indeed, the mechanical power produced by the user can be computed by the internal power (Pint) of the {user} system using the following expression previously detailed in Sauret, Bascou etal. (2012):