PRACTICE AND TRANSFER EFFECTS DURING FAST SINGLE-JOINT ELBOW MOVEMENTS IN INDIVIDUALS WITH DOWN-SYNDROME

Background and Purpose. The purpose of this study was to investigate t he effects of prolonged practice of a simple motor task (a fast, unidi rectional single-joint movement) on different indexes of motor perform ance in individuals with Down syndrome. Subjects. Eight individuals wi th Down syndrome were tested before and after practice involving 1,100 movements. Methods. The test consisted of three series of elbow flexi on movements. In the first series, the subjects were asked to move ''a s fast as possible'' over four distances. In the second series, the su bjects moved over one distance at a ''comfortable speed.'' The initial position of the elbow joint for these two series of movements was 55 degrees into flexion (full elbow extension equals 0-degree). In the th ird series, the subjects were also asked to move ''as fast as possible '' over two distances, but from another initial elbow position (73-deg rees into flexion). Results. After training over a 2-week period, all subjects improved their performance on all tasks as reflected by both kinematic and electromyographic data. In particular, they increased th e quantity of the agonist activity, decreased the antagonist onset lat ency, and doubled their peak velocity. They were able to transfer the improvement in their performance to the nontrained distances and to th e different starting position. Subjects decreased their movement time by proportionally decreasing both the acceleration and deceleration ti mes. Conclusion and Discussion. This study supports the idea that subj ects with Down syndrome can use patterns of muscle activation that are qualitatively indistinguishable from those used by individuals who ar e neurologically normal. With appropriate training, individuals with D own syndrome achieved similar levels of motor performance to that decr ibed in the literature for individuals who are neurologically normal.