Biomechanics of wheelchair propulsion during fatigue.

Musculoskeletal injuries can result from overuse or incorrect use of manual wheelchairs, and can hinder rehabilitation efforts. The purpose of this study was to investigate wheelchair propulsion biomechanics of spinal cord injured, non-athletic wheelchair users. We studied changes in the variables that occur with fatiguing wheelchair propulsion to determine how the user's physical characteristics and the state of fatigue influence risk of injury. Twenty male paraplegic patients were videotaped during propulsion to fatigue on a stationary, instrumented wheelchair positioned on a roller with adjustable frictional resistance. Peak handrim force was significantly correlated with concentric shoulder flexion and elbow extension isokinetic torques. Significant changes (p < 0.05) with fatigue were found in increased peak handrim force, decreased ulnar/radial deviation range of motion, and increased trunk forward lean. Of the three upper extremity joints, highest calculated joint moments were found in shoulder flexion (p < 0.05). These biomechanical results suggest that potentially harmful changes occur with fatigue, and that the shoulder may be the most prone to musculotendinous-type overuse injury.