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Previous literature has documented the alterations in the flexion-relaxation response of the lumbar extensor musculature to passive tissue elongation (PTE) and muscle fatigue (MF). There is no study, however, that has explored this response as a function of the combined effect of both PTE and MF, which is often seen in occupational settings. Twelve participants performed three experimental protocols on three different days to achieve (1) PTE, (2) MF and (3) PTE&MF (combined). Trunk kinematics and muscle activities were monitored to assess the effects of these protocols on the peak lumbar flexion angle and the lumbar angle of the flexion-relaxation of the trunk extensor muscles. Results showed responses to the uni-dimensional stresses (PTE and MF) consistent with those seen in the previous literature, while the combined protocol elicited responses that more closely matched the PTE protocol., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: The objective of this research was to determine the association between LBP that limited or interrupted fishing work and ergonomic low back stress measured by (1) self-reported task and (2) two ergonomic assessment methods of low back stress., Methods: Eligible participants were from a cohort of North Carolina commercial fishermen followed for LBP in regular clinic visits from 1999 to 2001 (n = 177). Work history, including crab pot and gill net fishing task frequency, was evaluated in a telephone questionnaire (n = 105). Ergonomic exposures were measured in previous study of 25 fishermen using two methods. The occurrence rate of LBP that limited or interrupted fishing work since last visit (severe LBP) was evaluated in a generalized Poisson regression model., Results: Predictors of severe LBP included fishing with crew members and a previous history of severe LBP. Among crab pot and gill net fishermen (n = 89), running pullers or net reels, sorting catch, and unloading catch were associated with an increased rate of LBP. Percent of time in forces >20 lb while in non-neutral trunk posture, spine compression >3,400 N, and National Institute of Occupational Safety and Health lifting indices >3.0 were associated with LBP., Conclusions: Tasks characterized by higher (unloading boat and sorting catch) and lower (running puller or net reel) ergonomic low back stress were associated with the occurrence of severe LBP. History of LBP, addition of crew members, and self-selection out of tasks were likely important contributors to the patterns of low back stress and outcomes we observed. Based on the results of this study, a participatory ergonomic intervention study is currently being conducted to develop tools and equipment to decrease low back stress in commercial crab pot fishing.

Commercial fishing is a job characterized by long hours in an unpredictable, dynamic natural environment and variable demands placed on the musculoskeletal system, requiring strength, coordination, and endurance. The focus of this project was in the quantification of the biomechanical stresses placed on the lumbar spine during the work activities of commercial crab fishermen. The continuous assessment of back stress (CABS) methodology was used to develop distributions describing the amount of time that each of the crew members on a two- or three-man crabbing crew spend at various levels of low back stress. The results of this analysis, expressed in terms of time-weighted histograms, show significant inter and intra-crewmember variability in the stress measures during regular daily work activities. For the three man crew, the captain has relatively low stress levels throughout the work day, while the mate performs high force (up to 30 kg), dynamic exertions while pulling the crab pots from the water up into the boat and high loads (20-40 kg) during the loading and unloading of the boat in the morning and evening, respectively. The third man of the crew experiences static awkward postures (forward flexed postures held for up to 5 min at a time) as he sorts and packs the crabs. For the two-man crew, the results show a more even distribution of the high stress activities between the crewmembers. The application of the results of this analysis for prioritization of work tasks for ergonomic intervention is discussed.

Alternative methods for viewing teeth while performing simulated dental procedures were investigated. The methods allowed participants to assume postures requiring less neck flexion than the standard direct view. One alternative used a video camera and monitor to view the mouth, the other incorporated 90 degrees prism glasses. The study was conducted in two parts: (1) novice participants performing a targeting task; (2) dental hygienists performing a scaling task on a mouth model. Posture and subjective perceptions were assessed in Parts 1 and 2. Muscle activity and performance were also assessed in Part 1. The alternative methods significantly reduced muscle activity, neck flexion, and discomfort, compared to the direct view. Preferences were a function of criteria (general, comfort, productivity, or accuracy). Previously, recommendations for reducing ergonomic risk factor exposure of dental professionals emphasized reducing time spent performing dental procedures. This study shows ergonomic interventions offer alternative means of risk exposure reduction.

Jobs with a high degree of variability in manual materials handling requirements expose limitations in current low-back injury risk assessment tools and emphasize the need for a probabilistic representation of the biomechanical stress in order to quantify both acute and cumulative trauma risk. We developed a hybrid assessment methodology that employs established assessment tools and then represents their evaluations in a way that emphasizes the distributions of biomechanical stress. Construction work activities in the home building industry were evaluated because of the high degree of variability in the manual material handling requirements. Each task was evaluated using the Revised NIOSH Lifting Equation, The University of Michigan Three-Dimensional Static Strength Prediction Program, and the Ohio State University Lumbar Motion Monitor Model. The output from each model was presented as time-weighted histograms of low-back stress, and the assessments were compared. The results showed considerable differences in what were considered high-risk activities, indicating that these 3 assessment tools consider the risk of low-back injury from different perspectives. The time-weighted distribution aspect of this methodology also contributed vital information toward the identification of high-risk activities. These results illustrate the necessity for more advanced low-back injury risk assessment techniques for jobs with highly variable manual materials handling requirements.

It is important to understand how trunk strength varies as a function of workplace factors so that the work environment can be designed to minimize the risk of low back injury. In this study maximal trunk torque production around the lumbosacral junction was measured in 44 subjects as trunk concentric and eccentric isokinetic velocity and trunk asymmetric line of action were varied. Trunk torque decreased by approximately 8.5% of maximum for every 15 deg of asymmetric trunk angle. Increases in concentric velocity decreased trunk strength, whereas increases in eccentric trunk velocity increased strength. Significant interactions were also found, and it was determined that the common finding that eccentric strength exceeds concentric strength is true only for forward trunk angles at all asymmetric angles. These results should have significant implications for the design of manual materials handling tasks.