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Biomechanics of wheelchair propulsion as a function of seat position and user-to-chair interface.

This study investigated the biomechanics of lever and hand-rim propulsion and the effects of seat position on propulsion mechanics. Nine able-bodied and six paraplegic spinal cord injured persons participated. Subjects performed hand-rim and lever propulsion on a wheelchair test simulator at a speed and load of 3km/hr and 7.5 watts/side, respectively. A 2 x 3 matrix of randomized seat positions was used. Three-dimensional motion measures of the trunk, shoulder, elbow, and wrist were collected over four-second sample periods for each seat position. Hub torque and stroke arc measurements were determined. Upper extremity motions were significantly different (p less than .05) for the two methods of propulsion. Hand-rim propulsion required less elbow motion, greater shoulder extension, less shoulder rotation and less arm abduction than lever propulsion. Both methods of propulsion required a substantial amount of internal rotation at the shoulder. Seat position changes had a greater effect on joint motion ranges when hand-rim propulsion was performed. No significant differences (p greater than .05) were found for trunk motion for the treatments. The findings provide additional information for development of a model for the optimization of wheelchair propulsion.