Shoulder joint kinetics during wheelchair propulsion on a treadmill at two different speeds in spinal cord injury patients

Study design: Prospective study using biomechanics patient data. Objectives: To analyze shoulder joint kinetics while propelling a wheelchair placed on a treadmill and compare shoulder joint net forces and moments when changing the speed of wheelchair propulsion on the treadmill. Setting: National Hospital for Spinal Cord Injury, Toledo, Spain. Methods: Sixteen subjects with thoracic spinal cord injury participated. A kinematic analysis system consisting of four camcorders (Kinescan-IBV) and a kinetic device that registered the contact force of the hand on the pushrim (SMART Wheel) were used. The wheelchair was propelled at 3 and 4 km h(-1) without any ramp. An inverse dynamic model allowed shoulder joint net forces and moments to be calculated from the contact force of the hand on the pushrim and kinematic data. Results: Increasing propulsion speed increased most of the temporal parameters of propulsion and pushrim kinetics and shoulder joint net forces and moments. Compared with other studies that used an ergometer or dynamometer at the same speed, the magnitude of the shoulder joint net forces and moments elicited by wheelchair propulsion on the treadmill were lower than obtained by wheelchair propulsion on other devices. Conclusion: Lower magnitude of shoulder joint forces and moments found on the treadmill may be due to the lower friction compared with the other devices reviewed. Shoulder joint forces and moments depended strongly on the propulsion speed, increasing in magnitude when speed increased from 3 to 4 km h(-1). Spinal Cord (2010) 48, 290-296; doi: 10.1038/sc.2009.126; published online 22 September 2009