Age-related differences in performance of stereotype arm movements: movement and posture interaction

Postural destabilizations in response to cyclic pull-and-push arm movements were compared in young and elderly subjects, with the goal of determining how age-related differences in postural stability influence strategies of cyclic arm movements made at different speeds, against different loads and while standing on support surfaces of different compliances. The results show that elderly subjects performed the experimental task more slowly with a lower mean movement frequency and a smaller amplitude. Despite of this fact, the elderly's upright posture was destabilized by this movement to a greater extent than in young subjects. The older adults exhibited lower damping of the disturbing torques produced by arm movements as evidenced by a higher amplitude of the center of foot pressure excursions. The results document close reciprocal motor and posture interaction and indicate that parameters of the voluntary movement task such as cyclic arm movements might be used as a sensitive measure of postural stability.