The effect of ship accelerations on three-dimensional low back loading during lifting and pulling activities

Manual materials handling on a moving platform, like a ship, might be a risk factor for the development of low back pain due to the influence of accelerations on low back loading. In the current simulation study, 3-D accelerations, measured on a frigate were applied to the kinematics of symmetrical and asymmetrical lifting movements and to a pulling task that had been performed under stable conditions. The aim was to find out to what extent low back loading is increased when the task execution is not adapted to the ship accelerations. Unfavorable timing, analyzed using the 99th percentile of predicted low back moments, resulted in only a moderate (up to 15%) increase of extending and total low back moments, and in a substantial increase of the twisting moment (up to 67%) during asymmetrical lifting. Moments in the pulling task were low and were relatively unaffected by ship accelerations, but adaptation of the movement pattern to prevent falling would be needed more often than during lifting. It furthermore appeared that a substantial reduction of low back loading by favorable timing is not a realistic option. Designing tasks in such a way that they are located midship would reduce the 99th percentile of predicted low back moments. During lifting, orienting the task in such a way that the feet are pointing sideward relative to the ship reduces the predicted peak twisting moment at the low back compared to pointing the feet forward or backward. Relevance to industry: Accelerations on a ship may influence safety and loading of workers during manual materials handling. This study investigates potential effects of moderate accelerations on low back loading during lifting and pulling tasks. It is shown that working midship reduces the risk of low back overloading, compared to working at the front deck.