The influence of load knowledge on lifting technique

TLDR

The study examined how knowing or not knowing the load influences lifting technique. Ten men lifted a box with varying weights (0, 150, 250, 300 N) with or without load knowledge, and the resulting kinetics and kinematics were measured using a force plate, motion capture, and a rigid‑body model. When the load was unknown, lifts produced a jerk‑like motion and higher L5–S1 flexion–extension moments, especially at 150 N, whereas at higher loads differences were minimal; thus incorrect load assumptions lead to unnecessary lower‑back loading. Keywords: Lifting technique, lower back pain, spinal loading, dynamic spine model, unknown load.

Abstract

Abstract The purpose of this study was to analyse the influence of load knowledge on lifting technique. Ten men lifted a box containing either no weight or weights of 150, 250 or 300 N with and without knowledge of what was inside the box. The kinetics and kinematics of the HA were analysed using a force plate, an optoelectronic motion analysis system, and 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–extension moment. At 150N there was also a significant increase in the speed of trunk extension with unknown weights, but the L5–S1 moment remained unchanged. At higher load levels there were only minor differences 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 anticipated lifting is performed with a ‘jerking’ motion, creating unnecessary loads on the lower back. Keywords: Lifting techniqueLower back painSpinal loadingDynamic spine modelUnknown load