Age related decline in postural control mechanisms.

In order to study voluntary and reflexive mechanisms of postural control, young and elderly persons were given large-fast and small-slow ankle-rotation postural disturbances while standing on a movable platform capable of measuring ground reaction forces. Large-fast rotations were employed to activate long-loop reflexes, and small-slow rotations were employed to tap the higher level sensory integration aspects of postural control. Overall, the elderly persons exhibited more perturbation induced sway and showed a slowing in voluntary, as opposed to reflexive mechanisms of correcting postural disturbance. For both age groups, reflexive mechanisms were found to be relatively intact. When small perturbations were given, the elderly persons swayed more than young participants and produced sporadic reflexive activity. Moreover, elderly persons did not adapt to the small perturbations and exhibited increased postural sway to repetitive presentation of the perturbation, whereas young participants substantially decreased their postural sway. These data demonstrate that elderly persons are at some disadvantage when posture is under the control of slower, higher level sensory integrative mechanisms.