Three-dimensional kinematics of the shoulder complex during wheelchair propulsion: a technical report

Methods for the three-dimensional (3-D) kinematic analysis of the shoulder complex (humerus relative to trunk) are presented and their use demonstrated in this analysis of shoulder motion during wheelchair propulsion. Ten subjects propelled two different wheelchairs (adjustable and conventional chairs) while the motions of the left arm and trunk were measured using a video tracking system. Eulerian angles described the sequence-dependent rotations of the humerus relative to the trunk. Wheel angular velocity and acceleration, hand position on the handrim, and duration of cycle subphases were also measured. Selected temporal and kinematic parameters were derived from the time-normalized average cycle of each subject on each wheelchair. Within-subject variation of these parameters according to wheelchair type were compared using a two-tailed t-test for paired observations. The adjustable chair made available a larger propulsion are compared with the conventional chair. Only the minimum amount of elevation demonstrated a significant difference between chairs (the conventional chair had a smaller minimum than the adjustable chair) at the corrected significance level of p < 0.001. Other differences, though not statistically significant, were still informative. Less shoulder internal rotation but more overall shoulder motion was observed during recovery phase in the adjustable chair as compared with the conventional chair. The methods presented for measuring the 3-D kinematics of the shoulder complex during wheelchair propulsion proved feasible for future use in studies that will address shoulder kinetics, energy requirements, wheelchair design, and chronic use disorders.