Glenohumeral joint kinematics and kinetics for three coordinate system representations during wheelchair propulsion

The shoulder plays a very important role during manual wheelchair propulsio n. Unfortunately, substantial numbers of manual wheelchair users eventually develop shoulder injury or pain. Recently, studies have begun to investiga te the etiology of wheelchair user shoulder injuries. This study compared t hree coordinate systems used to represent the shoulder during wheelchair pr opulsion. Our results show statistically significant differences between th e three shoulder representations analyzed. Differences are seen for individ uals and for the subjects as a group. Based upon our results, the fixed-z m odel appears preferable over the other representations due to its simplicit y, low hardware requirements, and the similarity of the results to the free representation. This article also provides some insight into maximal shoul der joint forces and moments recorded during manual wheelchair propulsion. Future work should include more sophisticated models of the shoulder comple x.