THE INFLUENCE OF LOAD KNOWLEDGE ON LIFTING TECHNIQUE

The purpose of this study was to analyse the influence of load knowled ge on lifting technique. Ten men lifted a box containing either no wei ght or weights of 150, 250 or 300 N with and without knowledge of what was inside the box. The kinetics and kinematics of the lift were anal ysed using a force plate, an optoelectronic motion analysis system, an d a rigid body link model. At ON lifting, the unknown load resulted in a jerk-like motion and a significantly increased peak L5-S1 flexion-e xtension moment. At 150 N there was also a significant increase in the speed of trunk extension with unknown weights, but the L5-S1 moment r emained unchanged. At higher load levels there were only minor differe nces between lifting techniques when knowing and not knowing the load. We conclude that lifts are approached assuming a certain weight, and that when the assumption is wrong and the load lighter than anticipate d lifting is performed with a 'jerking' motion, creating unnecessary l oads on the lower back.