The effects of obesity and standing time on postural sway during prolonged quiet standing.

This study examined the effects of obesity level, standing time and their interaction on postural sway during a prolonged quiet upright standing task. Ten extremely obese (BMI > 40 kg/m(2)) and 10 non-obese (18.5 kg/m(2) < BMI < 24.9 kg/m(2)) participants performed quiet upright standing on a force plate for over 18 min. Eleven postural sway measures were computed for each 1-min time interval based on the centre-of-pressure data from the force plate. ANOVA and regression analyses showed that for all the 11 postural sway measures, the extremely obese group had higher postural sway than the non-obese at the beginning of the prolonged standing task and postural sway increased significantly faster for the extremely obese group than the non-obese over time. The results suggest that obesity may impair postural control and may be a risk factor of balance loss and falls, especially during prolonged physical work activities. The research findings are relevant to identifying and reducing risks of balance loss and falls in various workplace settings for a wide variety of workers.