The Effects of Box Differences and Employee Job Experience on Trunk Kinematics & Low Back Injury Risk during Depalletizing Operations

Abstract

Workers from a local food distribution center were studied depalletizing boxes from a pallet. The objectives of this study were to determine the change in trunk kinematics associated with selecting boxes having different characteristics and to observe if there was a relationship between trunk kinematics and employee job experience. The boxes varied in terms of: size; presence/absence of handles; weight; and location on a pallet. Worker job experience also was recorded. Kinematic trunk motions and subsequent risk of low back disorder (LBD), assessed using a risk model, were studied as dependent measures. Results indicated that the weight and layer conditions influenced most of the kinematic variables. The size and handle conditions influenced fewer dependent measures. All main effects but the handle condition had an influence on LBD risk. Most of the significant interaction effects were related to layer, illustrating the tremendous influence that box location on a pallet had on trunk kinematics and LBD risk. In fact, at the bottom pallet layers, LBD risk was the same regardless of the weight lifted or the size of the box. In studying job experience, inexperienced workers were found to have LBD risk values that were, on average, 5% higher than the experienced group. This study has been successful at pinpointing which box parameters are worthy of consideration to include in a food distribution environment for the purposes of reducing the risk of work-related LBD.