Carrying loads and postural sway in standing: the effect of load placement and magnitude

This study investigated the effect that load magnitude, load location, and the dimensions that the base of support have on postural sway in standing while wearing a backpack, single strapped bag, briefcase, or purse. Subjects were instructed to carry a load of 10% or 20% of their body weight with either their feet spaced shoulder width apart or together for a period of 45 seconds. Medial/lateral and anterior/posterior center of pressure (COP) displacement and COP velocity were calculated. Overall, it was found that an increase in load magnitude produced an increase in postural sway and velocity of COP. In addition, a large increase in the medial/lateral COP velocity was observed when subjects carried a briefcase, single strapped bag, or purse. Additionally, a larger COP sway was recorded in conditions of standing with decreased base of support (feet together). These findings suggest the importance of considering the way we carry loads in order not only to place less strain on the body and to minimize our efforts, but to optimize postural control as well.