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

IntroductionCommercial fishing, cargo and passenger shipping, as well as offshore oil and gas 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.MethodsNineteen 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 (10 kg stable, 10 kg unstable, 15 kg stable, 15 kg unstable) onto a shelf in one lab condition and three different ship conditions (roll, quartering seas, and pitch) while wearing EMG electrodes and a Lumbar Motion Monitor (LMM). A repeated measures ANOVA was used to test for significant differences between loads and conditions for both electromyography (EMG) and LMM data.ResultsThe mean and maximum EMG (% Maximal Voluntary Contraction) showed significant differences across loads for all muscles except the left latissimus dorsi but showed a significant difference across conditions for the left latissimus dorsi only. For all loads, the pitch condition produced the largest maximum sagittal thoraco-lumbar velocities and the lab condition produced the smallest. There were significant mean and maximum thoraco-lumbar velocity differences across conditions in all three planes.ConclusionThe 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 increase significantly 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.Relevance to industryRisk management in maritime industries assumes tremendous importance as accidents at sea can result in personnel injury or death and environmental catastrophe. While much is known about the risks of manual materials handling in stable locations, little has been documented about the additive effects of working in motion rich environments. These results demonstrate that load and motion characteristics have specific effects upon operator performance and provide guidance for workstation design and administrative controls for lifting tasks on seagoing vessels.