Evaluating Ergonomic Stresses in North Carolina Commercial Crab Pot and Gill Net Fishermen

Abstract

There are challenges in evaluating physical demands of commercial fishing, including identifying sources of exposure variability. Low back biomechanical stresses associated with crab pot and gill net fishing were estimated; the variability was partitioned between and within fishing type, crew size, job title, and worker to improve understanding of risk factors for low back injury. The authors observed 162 person-hours of work among 25 North Carolina commercial fishermen on 16 crews. Postures and forces during fishing tasks were measured through direct and indirect observation using two methods to determine the percentage of time fishermen were exposed to high levels of low back stress. A multilevel linear model estimated exposure variability for the dependent variables by four nesting variables: fishing type, crew size, job title, and worker. Fishermen set and pulled crab pots or gill nets for 80% of the workday. Twenty-five percent of that time was spent handling gear. For both fishing types, handling heavy loads produced high peak compression values (3586 N to 5315 N) and high NIOSH lifting index values (3.3 to 5.4), but these tasks represent a small percentage of the overall work time (0 to 14%). The majority of exposure variation in non-neutral trunk posture and/or force > 9 kg, handling materials, NIOSH Lifting Index > 1, and Lumbar Motion Monitor probability of high-risk group membership > 70% was accounted for by fishing type (range 60 to 91%). Crew size was not an important source of variability for these six variables when fishing type and job title were accounted for in the model; but in the model restricted to crab pot fishing, crew size accounted for 51 to 88% of the variability in low back stress. For both models, job title comprised the majority of exposure variability for NIOSH Lifting Index > 3.0 (46 and 65%) and worker comprised the majority of variability for spine compression > 3400 N (54 and 65%). The magnitude and duration of musculoskeletal loads experienced by fishermen vary by the type of fishing and the tasks performed by the worker. Understanding this variability may help researchers target ergonomic interventions for this work population.

Keywords:

• exposure variability
• low back
• mixed model
• variance

ACKNOWLEDGMENTS

This work was supported by NIOSH grants and an NIEHS training grant. The parent study was supported through cooperative agreements between the Centers for Disease Control and Prevention and the North Carolina Department of Health and Human Services.

The authors acknowledge the help of Paula Bell, Steve Hutton, Raymond Vickers, Belinda Lee, and Judy Rafson, who participated in data collection. The authors acknowledge the significant contributions made by Mary Anne McDonald and Josh Levinson for their field work, including interviews, photographs, and videotape footage. The authors thank Scott Fulmer for his assistance with PATH and manuscript review. The authors acknowledge the help of Allison Marks, Gwansoeb Shin, Micca Pace, and Sue Wolf, who assisted with data collection. The authors thank the commercial fishermen who participated in the cohort study, and ethnographic study, and especially those fishermen who took us fishing with them.

The contents of this work is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute for Occupational Safety and Health (NIOSH) or the National Institute of Environmental Health Sciences (NIEHS).

Notes

^A PATH observations measured from videotape with researcher in the lab.

^B One 2-man crew measured crab pot and gill net fishing; n = 25 individual fishermen were observed.

^C Captain and mate on crab pot 3-man crew observed on 2 days.

^A Low back compression measured in Newtons at L5/S1 joint with University of Michigan 3D Static Strength Prediction Program.^{( 34 , 35 )}

^B NIOSH Lifting Index, object weight divided by recommended weight limit.^{( 32 )}

^C Probability of high-risk group membership measured with Ohio State University Lumbar Motion Monitor.^{( 33 )}

^D Percentage of sampled time during that PATH task and activity, % (se); non-neutral trunk includes flexion > 20 degrees, bend and twist > 20 degrees, or lateral flexion, bend, and twist > 20 degrees.

^E Other PATH tasks include pre and post fishing, load and unload, and docking and casting off.

^F Manual materials handling and includes lift, lower, carry, push/pull, slide, or hold.

^A Percentage of observed workday.

^B Lift, lower, carry, push/pull, slide, or hold.

^A Percentage of observed workday.