Effects of moving environments upon the physical demands of heavy materials handling operators

Introduction. Commercial fishing, cargo and passenger shipping, as well as offshore oil production are essential industrial activities in Canada, as well as other parts of the world. Mariners have to concentrate on maintaining balance as well as be prepared for motion-induced interruptions while performing work-related tasks, such as lifting. The purpose of this study was to assess the effects of a moving platform and load stability on recruitment of selected trunk musculature and thoraco-lumbar kinematics during common lifting tasks. Methods. Nineteen healthy male participants (22.78 +/- 1.72 years, 1.81 +/- .06 m, 82.42 +/- 12.08 kg) were recruited. Loads and conditions were manipulated to determine the effects of instability during manual materials handling tasks. Participants lifted four different loads (10kg stable, 10kg unstable, 15kg stable, 15kg unstable) onto a shelf in one lab condition and three different ship conditions (pure roll, quartering seas, and pure pitch) while wearing EMG electrodes and a Lumbar Motion Monitor (LMM). Statistical analysis including a repeated measures ANOVA was used to test for significant differences between loads and conditions for both electromyography (EMG) and LMM data. Results. The mean and maximum electromyography (%Maximal Voluntary Contraction) showed significant differences due to load for all muscles except the left latissimus dorsi but showed a significant difference due to condition for the left latissimus dorsi only. For all loads, the pitch condition produced the largest maximum sagittal velocities and the lab condition produced the smallest. There were significant mean and maximum velocity differences due to condition in all three planes. Conclusion. The pitch condition proved to be the most difficult condition to maintain stability regardless of whether or not a load was being handled. Motion direction of a platform, occurring during a lifting task, did not significantly increase muscular activity about the selected trunk musculature but did significantly increase thoraco-lumbar kinematics. Lifting unstable loads, compared to stable loads, in moving environments did significantly increase muscular activity about the selected trunk musculature but did not significantly increase thoraco-lumbar kinematics.