Postural sway during dual tasks in young and elderly adults.

BACKGROUND Previous studies have shown that healthy young adults are able to decrease their standing postural sway when an additional postural visual task, such as reading, is performed. OBJECTIVE In this study, we investigated postural sway during dual tasks in young and elderly adults. METHODS Twelve healthy active elderly adults (aged 65-75 years) and 12 healthy young adults (aged 22-39 years) participated in the study. The subjects performed different visual tasks while standing on a force plate. We varied the nature of the visual tasks (looking at a blank target versus a visual search task) and the distance of visual targets (near versus far). Center of pressure displacement obtained from the force plate data and kinematics of body segments obtained from a video analysis system were investigated. RESULTS Both groups presented significantly larger postural sway in the mediolateral direction during the eyes-closed condition as compared with the eyes-open condition. In the anteroposterior direction, this effect was observed only for the elderly group. Both groups had the same percentage correct in counting letters, but the elderly adults were significantly slower as compared with the young adults. The amplitude of postural sway was greater for the elderly adults than for the young adults in all conditions. However, both the young and the elderly adults exhibited significant reductions in sway during performance of the search task relative to sway during viewing of a blank target. The sway was also reduced for both groups during viewing a near target when compared to a distant target. CONCLUSIONS The results suggest that, despite the overall increase in postural sway with aging, subtle integration of visual information by the postural control system is not affected by aging. The present results support the idea that dual tasks do not necessarily lead to an increase in postural sway. This effect, found here in elderly adults, raises questions about widely held views in which age-related changes in postural sway are related to competition between postural control and other activities for central processing resources.