Short-term adaptations in co-ordination during the initial phase of learning manual wheelchair propulsion

The purpose of this study was to analyse adaptations in kinematics and muscle activity/co-contraction in novice able-bodied subjects during the initial phase of learning hand rim wheelchair propulsion. Nine able-bodied subjects performed three 4-min practice blocks on a wheelchair ergometer. The external power output and velocity were constant for all blocks, respectively 0.25 W x kg(-1) and 1.11 m x s(-1). Electromyography of 16 arm, shoulder, back and chest muscles and kinematics were measured. Some small changes in the segmental movement pattern were seen during the practice period. Moreover, an increase in muscle activity and co-contraction of several muscles was found over time. The hypothesis that subjects instinctively search for an optimum frequency, in which the recovery phase is related to the eigenfrequency of the arms and, therefore, the least muscle activity, could not be supported. Since co-contraction of antagonist pairs remained the same or even increased, the hypothesis that there would be a decrease in muscle co-contraction as a result of practice, was not confirmed. This study was probably too short for the novice subjects to explore this new task of wheelchair propulsion completely and reach an optimum in terms of cycle frequency and muscle activity/co-contraction.