Age-related changes in postural responses revealed by support-surface translations with a long acceleration-deceleration interval

Objectives: The objectives were to examine (a) whether surface translations with a long, compared to a short, acceleration-deceleration interval could reveal more age-related differences in postural control and (b) whether age-related differences were associated with reactive or anticipatory postural mechanisms. Methods: Ten older (66-81 years) and ten young adults (22-39 years) stood on a moveable platform that was unexpectedly translated in the backward direction. Subjects' electromyographic (EMG) and kinematic responses were recorded in response to translations with either a SHORT (100 ms) or LONG (2 s) acceleration-deceleration interval presented in either a predictable or random order. Results: Age-related differences in kinematic postural responses were greater during LONG compared to SHORT translations. However, both LONG and SHORT translations elicited a similar change in EMG latencies and amplitudes between the older and young adults. No age effects on the presentation order (predictable or random) of the translations were observed. Conclusions: LONG compared to SHORT surface translations magnify the age-related kinematic but not the EMG changes in reactive postural control. The anticipatory component of postural control was not affected by age. Significance: Translations with longer acceleration-deceleration intervals reveal more age-related differences in postural control, which are otherwise masked by the deceleration effects inherent to shorter translations. (C) 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.