Background: Frequent start movements occurred during the day, yielding high upper-extremity stress. The high incidence and impact of shoulder injury on daily life wheelchair use made it clinically relevant to investigate whether power-assisted propulsion is beneficial during the start.
Methods: Eleven hand-rim wheelchair users performed a start-movement in an instrumented wheelchair on a flat surface. Test order was randomly assigned to propulsion with and without power-assist. For each subject, parameters were averaged over 3 repeated starts. For statistical analysis Wilcoxon Signed Rank test was used.
Findings: Intensity of mechanical shoulder loading decreased during power-assisted propulsion for anterior (147.0 (44.8) versus 121.9 (27.4) N; effect size (r) = -.75), posterior (4.8 (14.1) versus 2.7 (11.6) N; r = -.64) and inferior directed forces (82.6 (27.9) versus 68.9 (22.6) N; r = -.78) and abduction (20.2 (14.6) versus 12.9 (7.8) Nm; r = -.88) and extension moments (203 (10.7) versus 13.7 (9.1 Nm; r = -.88). Peak resultant force at the rim significantly decreased from 133.5 (38.4) N to 112.2 (25.4) N (r = -.64) and was accompanied by significant decreased shoulder abduction (35.3 (6.7) versus 333 (6.8); r = -.67) and significant increased shoulder extension (13.6 (16.3) versus 20.3 (19.1); r = -.78) during power-assisted start-up.
Interpretation: Power-assist hand-rim wheelchairs are effective in reducing external shoulder load and partly effective in reducing force generation in extremes of shoulder motion during start-up. The use of power-assist wheels might reduce the risk of developing shoulder overuse injuries. (C) 2016 Elsevier Ltd. All rights reserved.
- Assistive technology
- Upper extremity