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 lowback pain due to the in.uence of accelerations on lowback 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 lowback moments, resulted in only a moderate (up to 15%) increase of extending and total lowback 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 lowback 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

Effect of ship motion on spinal loading during manual lifting

This study investigated the effects of ship motion on peak spinal loading during lifting. All measurements were done on a ship at sea. In 1-min trials, which were repeated over a wide range of sailing conditions, subjects lifted an 18 kg box five times. Ship motion, whole body kinematics, ground reaction forces and electromyography were measured and the effect of ship motion on peak spinal moments and compression forces was investigated. To investigate whether people time their lifts in order to reduce the effect of ship motion on back loading, trials were performed at a free and at a constrained (lifting every 10s) work pace. With increase of the (local) vertical ship acceleration, increased moments and compression forces were found. Furthermore, lifting at a free work pace did not result in smaller effects of ship motion on spinal moments and compression forces than working at a constrained work pace