Trade-offs between Trunk Flexion,Hip Flexion,and Knee Angle in Lifting below Waist Level

Abstract

This study quantified trunk, hip and knee kinematics during realistic lifting to determine the influence of origin height on lifting style. Ten male participants lifted boxes from several origins ranging from the floor to waist height. The three-dimensional motions of the trunk, hip and knee were recorded. Maximum trunk flexion, knee flexion, and hip flexion increased as lift origin decreased (closer to the floor). Back, knee and hip sagittal angles showed significantly increased correlations as the origins became closer to the floor. Subjects appeared to coordinate their hips, back and knees during the lift for origins below knee height. For lifts above knee height, the lifting style resembled more of a stoop lift while lifts originating below knee height were more of a squat lift. As none of the conditions resulted in pure squat or stoop lifting, discretion is needed in applying the results of pure squat or pure stoop lifting studies to the workplace.