Postural Stability While Holding Loads in Various Postures

Abstract

Stability while handling loads is an important issue in the prevention of injuries. This study investigated the effects of load positioning on recovery from an unexpected balance disturbance while standing upright holding loads. Fifteen subjects were tested while holding a box in one of five postures. An empty box and a 25 lb box were tested. Subjects stood on a posture platform while perturbations of the supporting surface were induced. Postural sway was recorded via center of pressure displacements calculated from three dimensional foot forces. It was found that laden standing with the heavier load resulted in increased sway magnitude and slower sway velocities than unladen standing. The load position also affected stability. Raising the center of gravity of the body-and-load system appears to increase sway. These results require consideration when designing safe material handling tasks, especially if the supporting surface is unstable or if slip potential is present.