Reducing biophysiological strain with incremental levels of pushrim-activated power-assist in manual wheelchair users

Objective This study investigated differences in biophysiological strain across six levels of pushrim-activated power-assisted wheelchair (PAPAW) support.Design Fourteen experienced wheelchair users (mean age 42.2 ± 14.0 years) performed six 4-minute submaximal propulsion trials at a fixed speed (0.56, 0.83, or 1.11 m/s) and resistance (0.21 W/kg body mass). Each trial used a different assistance level, none, very low, low, medium, high, and very high, in counterbalanced order. Physiological strain was assessed via energy expenditure, heart rate, and perceived exertion. Biomechanical parameters, including work per push and propulsion forces, were derived from a force-instrumented wheelchair ergometer.Results Generalised Linear Mixed Models revealed that increased assistance level significantly reduce metabolic outcomes, including energy expenditure and heart rate (p ≤ 0.001). Kinetic and temporospatial variables such as mean and peak push forces, work per push, contact angle and push time also significantly decreased with higher assistance (p ≤ 0.016). Movement variability and asymmetry increased during higher assistance levels (p = 0.002).Conclusion Increasing PAPAW assistance resulted in an incremental reduction in both physiological and biomechanical strain in wheelchair users. The results might be used to tailor the correct amount of support to individual needs. Future research should aim to identify optimal balance, one that alleviates physical strain without compromising the user’s overall fitness.Implications for RehabilitationHigher assistance levels of Pushrim-Activated Power-Assisted wheels lead to reductions in physiological demands and decreased push forces, work per push, contact angle and push time. Confirming that an increased level of assistance decreases the biophysical strain of manual wheelchair propulsion.Yet, propulsion with Pushrim-Activated Power-Assisted wheels causes a movement variability and asymmetry compared to unassisted manual wheelchair propulsion, which may have implications for driving behaviour and control.