Effects of carried weight on random motion and traditional measures of postural sway.

The purpose of the study was to investigate the effects of load weight carried by soldiers upon postural sway. Fourteen US Army enlisted men participated. Postural sway and muscle activity were measured while participants stood on a force plate. The load weight conditions, comprised of Army clothing and load-carriage equipment were 6, 16, and 40 kg. With an increase in load weight, stabilogram-diffusion analysis revealed that random movement of postural sway decreased. Also, with an increase in load weight, center of pressure excursions increased linearly but muscle activity changed minimally. In short, increasing load weight challenged the load carriers' stability, reduced the randomness of postural sway and required the load carriers to exert greater control of the load in order to maintain balance.