Is Changing Box Weight an Effective Ergonomic Control?

With the rising costs of low back injuries, one low cost ergonomic solution would be to reduce the weight. But, limited research has investigated how the worker interacts with the box. This study evaluated how lifting different box weights effects the trunk kinematics, horizontal moment arm, and resulting spinal loads. Fifteen participants lifted a box weighing 9.1, 11.8, 14.5, 17.2, 20.0, 29.9, 32.7, 35.4, 38.1, and 41.7 kg., from knee height, carried it a distance of five feet, and placed it on a shelf at elbow height. The present study quantifies the utility of reducing the weight lifted. Small changes in weight were found to only slightly influence the trunk kinematics and spinal loads. The accuracy of the spinal load estimates were found to be influenced by the trunk dynamics and changes in horizontal moment arm, especially for the lighter weights evaluated in this study. These results can be used to establish potential weight limits to assist in the ergonomic redesign of a manual material handling task.