JMIR Publications

ABSTRACT

This research assesses the ergonomic design of a dual-purpose stairclimbing wheelchair, focusing on improving usability and comfort for both stairclimbing and plane surface navigation. An anthropometric survey of 20 male participants provided data on reach and clearance, using 5th and 95th percentile measurements to ensure the wheelchair accommodates a wide range of body sizes. A plane surface movement study involved nine participants, seven healthy individuals and two with paraplegia—who navigated a simulated urban course. The course included a 5° ramp, a sharp 90° turn, and narrow passages, with performance evaluated over three trials. Metrics included task completion times and subjective ratings of ride easiness. The ramp (R) and 90° turn (T1) proved most challenging, taking the longest to complete due to the wheelchair’s 65 kg weight—driven by its stairclimbing mechanism—and its large turning radius of approximately 1450 mm. Participants rated driving control moderately (6/10), but comfort scored lowest, largely due to a seat tilted for stairclimbing stability, which compromised comfort on flat surfaces. A complementary Taguchi-based experiment examined ergonomic factors in lever propulsion, testing torso angle (λ), lever distance (L), and lever orientation (ψ) effects on muscle activation recorded using Surface Electromyography (sEMG). Maximum Voluntary Contraction (MVC) was measured across four muscles: Biceps Brachii Long Head (BBL), Triceps Brachii Long Head (TBL), Brachioradialis (BRS), and Posterior Deltoid (PDT). Results showed a straight torso (λ = 0°) reduced strain, especially on BRS, while a lever distance of ~50 mm and neutral to slightly supinated orientation (ψ = 0° to 30°) optimized muscle effort. Data visualizations, including heatmaps and 3D surface plots, informed an ergonomic recommendation of λ = 0°, L = 37.5 mm, and ψ = 15°. Findings underscore design trade-offs, suggesting reductions in weight and size, alongside an adjustable seat tilt, to balance stairclimbing capability with everyday usability. Future work should refine these parameters and test across broader demographics.