Mechanical load on the upper extremity during wheelchair activities

Objective: To determine the net moments on the glenohumeral joint and elbow joint during wheelchair activities. Design: Kinematics and external forces were measured during wheelchair activities of daily living (level propulsion, riding on a slope, weight-relief lifting, reaching, negotiating a curb) and processed in an inverse dynamics biomechanic model. Setting: Biomechanics laboratory. Participants: Five able-bodied subjects, 8 subjects with paraplegia, and 4 subjects with tetraplegia. Main Outcome Measure: Net moments on the glenhummeral joint and elbow joint. Results: Peak shoulder and elbow moments were significantly higher for negotiating a curb and weight-relief lifting than for reaching, level propulsion, and riding on a slope. Overall, the elbow extension moments were significantly lower for subjects with tetraplegia than for those with paraplegia. Conclusions: The net moments during weight-relief lifting and negotiating a curb were high when compared with wheelchair propulsion tasks. Taking the effect of frequency and duration into account, these loads might imply a considerable risk for joint damage in the long term.