G. Desroches, R. Aissaoui, M. Boukhelif, and D. Bourbonnais (Canada)
Manual wheelchair propulsion, measurement uncertainty, shoulder kinetics, simulation
Joint forces and moments are often used to estimate the load sustained by joints during a specific task. However, their accuracy is dependent upon the validity of the instrumentation. The SMARTwheel is often used to record the forces and moments exerted by the hand during manual wheelchair propulsion. These forces and moments are then used as inputs to an inverse dynamic model to estimate joint kinetics. A study has shown that this force sensing device as a certain uncertainty (~1-5%) depending on the variable. Yet no information is available on the impact on the shoulder load of this measurement uncertainty. The purpose of this paper is to compute the uncertainty of the forces and moments measured by the SMARTwheel during manual wheelchair (MWC) propulsion and determine the impact on shoulder kinetics. Fourteen elderly MWC users were tested in an ergometer. They had to propel at submaximal speed (~ 1m\s) and kinematic and kinetic data were recorded for 10 seconds. Uncertainties on the pushrim forces and moments were computed and added to the initial pushrim kinetics. Inverse dynamic model was used to estimate shoulder joint forces and moments for the initial kinetics condition without and with uncertainty. The results suggest that the uncertainty accounts for variability less than 1 N for the forces and 1 Nm for the moments at the shoulder.
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