Effects of user's actions on rolling resistance and wheelchair stability during handrim wheelchair propulsion in the field.

Currently, rolling resistance and wheelchair stability during manual wheelchair propulsion can be assessed from the loads applied on the front and rear wheels, which are determined in a static condition. However, a user's actions on the wheelchair would change these loads during locomotion, which should affect both the rolling resistance and wheelchair stability. The goal of this study was to verify these assumptions and assess how much the rolling resistance and wheelchair stability are affected by the user's actions during propulsion. For that purpose, a mechanical model was developed using measurements of an instrumented wheelchair equipped with several six-component dynamometers. Experiments were performed by three subjects propelling the instrumented wheelchair over flat ground. The results showed variations over wide ranges of the fore-aft distribution of the total load, rolling resistance, wheelchair stability, wheelchair velocity and mechanical power dissipated by the rolling resistance during the propulsion cycle. In addition, the time courses of all these variables differed with the subject. Finally, this study demonstrated the possibility of assessing intra-cycle values of both rolling resistance and wheelchair stability during manual wheelchair displacements in the field, which provides a technical step towards evaluating a wheelchair user in his daily environment.