JMIR Publications

ABSTRACT

Background:

Manual wheelchairs designed for stairclimbing offer enhanced accessibility but often compromise on comfort and usability during plane surface navigation. Limited research has explored the ergonomics of lever propulsion in such dual-purpose wheelchairs, particularly using surface electromyography (sEMG) to assess muscle strain and inform design optimization.

Objective:

The objective of this study was to evaluate the ergonomic design of a novel stairclimbing wheelchair, focusing on comfort and usability during plane surface movement and lever-based stairclimbing, using anthropometric measurements, subjective feedback, and sEMG to recommend design improvements.

Methods:

An anthropometric survey of 20 male participants provided data on reach and clearance, using 5th and 95th percentile measurements to inform wheelchair dimensions. Nine participants (seven healthy, two with paraplegia) navigated a simulated urban course with a 5° ramp, 90° turn, and narrow passages, with task completion times and subjective ride easiness rated on a Likert scale. For lever-based stairclimbing analysis, 7 abled male subjects performed a Taguchi-based experiment that assessed lever propulsion ergonomics, testing torso angle (λ: 0°, 30°, 45°), lever distance (L: 0 mm, 50 mm, 100 mm), and lever orientation (ψ: -30°, 0°, 30°) on four muscles (Biceps Brachii Long Head, Triceps Brachii Long Head, Brachioradialis, Posterior Deltoid) using sEMG. Maximum Voluntary Contraction (MVC) data were analyzed with heatmaps and 3D surface plots.

Results:

The plane surface study revealed that the ramp and 90° turn were the most challenging tasks, taking the longest due to the wheelchair’s 65 kg weight and 1450 mm turning radius. Subjective ratings scored driving control at 6/10, with comfort lowest due to a seat tilt designed for stairclimbing stability. sEMG results showed a straight torso (λ=0°) minimized strain, especially on Brachioradialis, while a lever distance of ~50 mm and neutral to slightly supinated orientation (ψ=0° to 30°) optimized muscle effort. Optimal settings were averaged at λ=0°, L=37.5 mm, ψ=15°, reducing strain across muscles.

Conclusions:

The study highlights trade-offs in stairclimbing wheelchair design, recommending weight reduction, a compact form factor, and adjustable seat tilt to enhance plane surface usability without compromising stairclimbing functionality. The ergonomic settings of a straight torso, moderate lever distance, and slight supination minimize muscle strain, improving comfort and efficiency. Future research should validate these findings across diverse populations and refine additional design parameters like seat adjustability. Clinical Trial: Institute Ethics Committee Communication Number: IITK/IEC/2024-25/I/29