Assessment of Muscle Activity During Uphill Propulsion in a Wheelchair Equipped with an Anti-Rollback Module

Uphill wheelchair propulsion requires considerable upper-limb effort and often leads to rapid fatigue, limiting user mobility and independence. Therefore, mechanical solutions that enhance propulsion safety and efficiency are essential. This study aimed to evaluate the effect of an anti-rollback module on upper-limb muscle activity and user load during uphill propulsion. Eight male participants propelled a manual wheelchair under three conditions: without the module (NAR), with a flexible roller (EAR), and with a stiff roller (SAR). Electromyographic (EMG) signals were recorded from four upper-limb muscles—anterior deltoid, triceps brachii, biceps brachii, and extensor carpi radialis—along with propulsion kinematics. The analyzed parameters included the number of push cycles, cycle duration, normalized muscle activity (EMGnorm), cumulative muscle load (CML), and its rate over time (CML/s). On average, participants performed 13.4 push cycles in NAR, 14.3 in EAR, and 14.4 in SAR, with corresponding cycle durations of 1.22 s, 1.59 s, and 1.39 s. The EAR configuration reduced fluctuations in EMG amplitude and CML/s compared to NAR, indicating smoother and more stable propulsion. No significant differences in mean EMGnorm or total CML were observed (p > 0.99). The flexible anti-rollback module improved propulsion stability and control without increasing muscle effort, suggesting its potential benefits for safer and more efficient manual wheelchair use on inclines.