Article

It has been suggested that feedforward planning of gait and posture is diminished
in older adults. Motor adaptation is one mechanism by which feedforward commands
can be updated or fine-tuned. Thus, if feedforward mechanisms are diminished in
older adults, motor adaptation is also likely to be limited. The purpose of the
study was to compare the ability of healthy older versus young adults in
generating a voluntary stepping motor adaptation in response to a novel visual
sensory perturbation. We recorded stepping movements from 18 healthy older and 18
young adults during baseline and adaptation stepping blocks. During baseline, the
stepping target remained stationary; in adaptation, a visual perturbation was
introduced by shifting the target laterally during mid-step. We compared
adaptation between groups, measured by improvements in endpoint accuracy and
movement duration. Older adults adapted stepping accuracy similarly to young
adults (accuracy improvement: 29.7 + or - 27.6% vs. 37.3 + or - 22.9%, older vs.
young group respectively, p = 0.375), but showed significant slowness during
movement. Thus older adults were able to achieve accuracy levels nearly
equivalent to younger adults, but only at the expense of movement speed, at least
during the early adaptation period (movement duration: 1143.7 + or - 170.6 ms vs.
956.0 + or - 74.6 ms, p < 0.001). With practice, however, they were able to
reduce movement times and gain speed and accuracy to levels similar to young
adults. These findings suggest older adults may retain the ability for stepping
adaptations to environmental changes or novel demands, given sufficient practice.
CI - Copyright 2009 Elsevier B.V. All rights reserved.

Langue : ANGLAIS