Inertial and frictional influences of instrumented wheelchair wheels

BACKGROUND: Instrumented wheelchair wheels can be used to study the kinematics and kinetics of manual wheelchair propulsion. The objective of this study was to evaluate the impact of instrumented wheels on the inertial and frictional parameters of a wheelchair system. METHODS: This study compared mechanical parameters of an ultralightweight rigid frame wheelchair configured with pairs of SMARTwheels and spoke pneumatic wheels and loaded with an ISO 75 kg wheelchair dummy. Rectilinear and turning inertia of the occupied wheelchair and the rotational inertia of drive wheels were measured. A coast-down test measured frictional energy loss during straight and turning trajectories. FINDINGS: The addition of instrumented wheels increased occupied system mass by about 6% and turning inertia by about 16%. Frictional energy loss increased by over 40% in a straight trajectory and over 30% during turning. INTERPRETATION: Addition of instrumented increased the inertia and frictional energy loss of the wheelchair system. These relative effects will impact the wheelchair operator and increase the instantaneous propulsion torque during wheelchair maneuvers. The impacts will be less under conditions involving little or no change in velocity. Researchers should be encouraged to report changes in mass and weight distribution induced by addition of instrumented wheelchair wheels.