Purpose: To determine the prevalence and severity of manual wheelchair rear wheel misalignment in community-dwelling manual wheelchair users and estimate the associated increases in rolling resistance (RR) and risk of repetitive strain injuries (RSIs).
Materials and Methods: Data were collected in an outpatient rehabilitation clinic, a university research laboratory, and at adaptive sporting events in the United States. Two hundred active, self-propelling man- ual wheelchair users were recruited. Angular misalignment (referred to as toe angle) while the wheelchair was loaded with the user, and the difference between the maximum and minimum toe angle (referred to as slop) with the wheelchair unloaded.
Results: Average results for toe angle and slop (movement in the rear wheels) were 0.92 and 0.61 degrees, respectively. Using a lab-based testing method, we quantified the impact of increased RR forces due to misalignment in increased RR forces. Our results indicate that the average toe angle while under load and slop, without loading, measured in the community increase required propulsion force by 3.0 N. Combined toe angle and slop (i.e., the worst-case scenario) added increased propulsion force by 3.9 N. Conclusions: We found that rear-wheel misalignment was prevalent and severe enough that it may increase the risk for RSIs and decrease participation. To mitigate this issue, future work should focus on reducing misalignment through improved maintenance interventions and increased manufacturing qual- ity through more stringent standards.