Age differences in postural sway during volitional head movement

Objective: To examine the role of a volitional self-paced head-turn movemen t on the postural sway characteristics of healthy young and elderly subject s. Design: Cross-sectional design. Setting: Motor control research laboratory. Subjects: Ten young adults and 10 elderly subjects. Main Outcome Measures: Postural sway characteristics of each subject were e xamined using a Kistler force platform. Each subject was tested under four experimental conditions: (1) static postural sway with vision; (2) static p ostural sway without vision; (3) postural sway with vision and self-paced h ead-turn movement; and (4) postural sway with no vision and a self-paced he ad-turn movement. Subjects performed six 15-second trials in each experimen tal condition. Dependent variables analyzed on each trial were mean sway am plitude tin millimeters), sagittal sway standard deviation, lateral sway st andard deviation, and frequency of sway tin hertz). Results: During the static conditions (eg, no voluntary movement), the youn g subjects produced significantly less postural sway than the elderly in bo th the vision condition (sway amplitude in the young, 3.80mm; in the elderl y, 4.89mm) and the no-vision condition (young, 5.44mm; elderly, 5.95 mm). T his increased sway was the result of greater lateral sway in the elderly fo r the vision condition (3.73 vs 2.68mm), and greater sagittal sway for the elderly in the no-vision condition (5.55 vs 4.70mm). There were no signific ant differences between the groups in the frequency of sway. When asked to initiate and complete the head-turn, elderly subjects significantly increas ed their mean sway amplitude and decreased their frequency of sway, whereas the young subjects did not significantly alter their postural sway profile s. Conclusions: These results demonstrate different postural sway control stra tegies for young acid elderly subjects when asked to perform volitional mov ements. (C) 1999 by the American Congress of Rehabilitation Medicine and th e American Academy of Physical Medicine and Rehabilitation.