Reducing upper-limb strain in rehabilitation: usability evaluation of a detachable bidirectional propulsion device for spinal cord injury users

To determine whether a detachable bidirectional (push-pull) propulsion module for manual wheelchairs can be rapidly learned, perceived as safe, and accepted by long-term users with spinal cord injury (SCI). Twenty adult SCI wheelchair users (mean age 59.4 ± 11.2 yr; wheelchair experience 20.1 ± 12.3 yr) propelled their chairs, equipped with the module, along a 20 m indoor corridor, completing five push and five pull trials after ∼10 min of familiarization and seat-belt fitting. Usability was assessed using a 45-item, 7-domain Likert scale (1 = strongly disagree, 5 = strongly agree) with excellent internal consistency (Cronbach's <i>α</i> = 0.927). Across domains, learnability, safety, user satisfaction, effectiveness, and efficiency were rated highly, with mean scores above 4.3 on a 5-point scale. Universality received comparatively lower ratings, reflecting cost considerations and adaptability to different contexts. The highest-rated single item was ease of understanding propulsion-mode switching, while willingness to use the device considering cost was lowest. No falls or entrapment events occurred during the trials. Overall, the push-pull module was intuitive, safe, and efficient after minimal training, with potential to diversify upper limb loading patterns and reduce shoulder strain in manual wheelchair users. Some participants noted challenges related to device width, weight (∼8 kg), and cost, indicating the need for further design optimization and structured training resources prior to widespread implementation.