Shoulder and elbow motion during two speeds of wheelchair propulsion: a description using a local coordinate system.

Individuals who propel wheelchairs have a high prevalence of upper extremity injuries. To better understand the mechanism behind these injuries this study investigates the motion of the shoulder and elbow during wheelchair propulsion. The objectives of this study are: (1) To describe the motion occurring at the shoulder and elbow in anatomical terms during wheelchair propulsion; (2) to obtain variables that characterize shoulder and elbow motion and are statistically stable; (3) to determine how these variables change with speed. The participants in the study were a convenience sample of Paralympic athletes who use manual wheelchairs for mobility and have unimpaired arm function. Each subject propelled an ultralight wheelchair on a dynamometer at 1.3 and 2.2 meters per second (m/s). Biomechanical data was obtained using a force and moment sensing pushrim and a motion analysis system. The main outcome measures investigated were: maximum and minimum angles while in contact with the pushrim, range of motion during the entire stroke and peak accelerations. All of the measures were found to be stable at both speeds (Cronbach's alpha > 0.8). The following measures were found to differ with speed (data format: measure at 1.3 m/s +/- SD; measure at 2.2 m/s +/- SD): minimum shoulder abduction angle during propulsion (24.5 degrees +/- 6.7, 21.6 degrees +/- 7.2), range of motion during the entire stroke in elbow flexion/extension (54.0 degrees +/- 9.9, 58.1 degrees +/- 10.4) and shoulder sagittal flexion/extension (74.8 degrees +/- 9.4, 82.6 degrees +/- 8.5), and peak acceleration in shoulder sagittal flexion/extension (4044 degrees/s2 +/- 946, 7146 degrees/s2 +/- 1705), abduction/adduction (2678 degrees/s2 +/- 767, 4928 degrees/s2 +/- 1311), and elbow flexion/extension (9355 degrees/s2 +/- 4120, 12889 degrees/s2 +/- 5572). This study described the motion occurring at the shoulder and elbow using a local coordinate system. Stable parameters that characterize the propulsive stroke and differed with speed were found. In the future these same parameters may provide insight into the cause and prevention of shoulder and elbow injuries in manual wheelchair.