Rapid aimed limb movements: age differences and practice effects in component submovements.

Two experiments are reported in which younger and older adults practiced rapid aimed limb movements toward a visible target region. Ss were instructed to make the movements as rapidly and as accurately as possible. Kinematic details of the movements were examined to assess the differences in component submovements between the 2 groups and to identify changes in the movements due to practice. The results revealed that older Ss produced initial ballistic submovements that had the same duration but traveled less far than those of younger Ss. Additionally, older Ss produced corrective secondary submovements that were longer in both duration and distance than those of the younger subjects. With practice, younger Ss modified their submovements, but older Ss did not modify theirs even after extensive practice on the task. The results show that the mechanisms underlying movements of older adults are qualitatively different from those in younger adults.