Enhancing Manual Wheelchair Propulsion: Incremental Assistance Levels of Pushrim-Activated Power-Assist Proportionally Reduce Physiological and Biomechanical Demands in Non-Disabled Participants

Abstract

This study assessed the effect of increasing assistance levels of a Pushrim-Activated Power-assisted Wheelchair (PAPAW) on the physiological and biomechanical demands in non-disabled participants propelling a manual wheelchair on an instrumented ergometer. This cross-sectional study included twenty-four non-disabled participants (aged $21.1~\pm ~1.4$ years) who performed 4 submaximal trials of 4-minutes propulsion (at 1.11m/s and 0.21W/kg body mass resistance) using no, low, medium and high power-assist modes of a PAPAW in counterbalanced order. Physiological strain, in terms of metabolic energy expenditure, heart rate and perceived exertion, was examined, along with the force and velocity data from the wheelchair ergometer and PAPAW. Repeated measures ANOVA revealed that metabolic energy expenditure decreased significantly with each incremental step of assistance (no: $299~\pm ~43$ W, low: $250~\pm ~37$ W, medium: $240~\pm ~44$ W, high: $224~\pm ~38$ W, p $\le 0.001$ ), accompanied by similar reductions in heart rate and perceived exertion. Similarly, work per push decreased with each step (no: $16.9~\pm ~6.2$ J, low: $7.9~\pm ~2.8$ J, medium: $6.4~\pm ~2.5$ J, high: $5.5~\pm ~1.4$ J, p $\le 0.001$ ). This can be explained by reductions in propulsive forces, which reached a floor effect with no further reduction between medium and high assistance levels, and a decreased contact angle. The level of PAPAW assistance progressively reduces the metabolic and biomechanical demands of manual wheelchair propulsion, potentially lowering the risk of overuse injuries and enhancing participation in daily activities and society. Further research should explore the optimal assistance level that reduces strain while maintaining physical fitness during everyday mobility.