A lightweight wheelchair propulsion dynamometer for improving user energy efficiency and mobility

The population of manual wheelchair users is growing; the vast majority of users are due to spinal cord injury, often presenting in young adults. Propulsion forces must be produced by the upper body only; such repetitive forces impact the shoulder and elbow joints, leading to long term pain and injury. This also has an effect on mobility, with consequential socio-economic implications. Training in the style of propulsion, especially from an early age, may lead to more efficient propulsion and reduced injury and pain. To measure the forces of propulsion and calculate energy expenditure, the connecting pins between a wheelchair pushrim and drivewheel were replaced with three multi-axis load cells able to measure the real time forces due to pushing. This paper reports the development of the Sensewheel Mk1 propulsion dynamometer: concept, load cell design and modelling, strain gauging and instrumentation, assembly, calibration and sample recorded data.