Enhancement of posture sway with backpack weight carrying by eye closure and reduced support polygon surface

Abstract Objective In a previous study (Hanan and Jammes, Obesity Medicine, 2019) we showed that backpack carrying mimicking obesity elicited marked changes in postural sway during upright standing. Our objective was to study, separately or combined, the postural effect of weight carrying, eye closure, and/or reduced support polygon when healthy people stayed upright for 10 min. Methods Young adults had to maintain their eyes open or closed when standing upright for 10 min with or without added backpack weights. The postural effects of a 30–35% reduction of the support polygon (directed feet position) were also examined. We measured the surface and length of displacement of the centre of pressure (CoP), and amplitude and velocity of changes of its deviations in mediolateral and anteroposterior directions. Results Eye closure during weight carrying in the condition of spontaneous feet placement significantly increased the CoP length and surface and the anteroposterior and mediolateral CoP deviations. Reduction of the support polygon (directed position) during weight carrying significantly increased both the CoP surface and the mediolateral CoP deviation. Conclusion Altered postural control with backpack weight carrying is augmented by reduction of the support polygon and the suppression of visual information. These conditions should be avoided in obese subjects. Clinical trial registration CPP Sud Mediterranee 1, September 9th 2015, N° 2014-AO1969-38.