John R. Heberger

Examining the Interaction of Force and Repetition on Musculoskeletal Disorder Risk: A Systematic Literature Review

Objective: Our aims were (a) to perform a systematic literature review of epidemiological studies that examined the interaction of force and repetition with respect to musculoskeletal disorder (MSD) risk, (b) to assess the relationship of force and repetition in fatigue failure studies of musculoskeletal tissues, and (c) to synthesize these findings. Background: Many epidemiological studies have examined the effects of force and repetition on MSD risk; however, relatively few have examined the interaction between these risk factors. Method: In a literature search, we identified 12 studies that allowed evaluation of a force-repetition interaction with respect to MSD risk. Identified studies were subjected to a methodological quality assessment and critical review. We evaluated laboratory studies of fatigue failure to examine tissue failure responses to force and repetition. Results: Of the 12 epidemiological studies that tested a Force × Repetition interaction, 10 reported evidence of interaction. Based on these results, the suggestion is made that force and repetition may be interdependent in terms of their influence on MSD risk. Fatigue failure studies of musculoskeletal tissues show a pattern of failure that mirrors the MSD risk observed in epidemiological studies. Conclusions: Evidence suggests that there may be interdependence between force and repetition with respect to MSD risk. Repetition seems to result in modest increases in risk for low-force tasks but rapid increases in risk for high-force tasks. This interaction may be representative of a fatigue failure process in affected tissues.

Analysis of Fatalities During Maintenance and Repair Operations in the U.S. Mining Sector

OCCUPATIONAL APPLICATIONS This analysis identified patterns in fatalities during maintenance and repair operations in mining. U.S. mining maintenance and repair fatal reports (2002–2011) were reviewed and used to develop a classification scheme. Fatalities were classified using this scheme, and proximal causes, tasks performed, and contributing factors were identified, as well as differences in patterns between coal and metal/nonmetal mines. Based on the results, possible interventions to reduce fatality occurrences are discussed. Primary suggestions include ensuring that workers are knowledgeable about and understand the importance of following proper de-energizing and lock out/tag out procedures, particularly in coal mines where the proportion of electrical-related deaths is significantly higher than in metal/nonmetal mines, and proper blocking procedures. Effort should be made to ensure that safety equipment and personal protective equipment are available and used where needed, especially in metal/nonmetal mines where a greater chance exists for objects or miners to fall from heights. TECHNICAL ABSTRACT Background: Maintenance and repair work in mining is particularly hazardous and yet has received little focus in ergonomics research. Purpose: In this article, an attempt has been made to determine if patterns can be identified to categorize maintenance and repair fatalities in mining, to compare occurrence of fatalities between coal and metal/nonmetal sectors, and to use this information to identify safety deficiencies and associated proposed remedial measures. Methods: A classification scheme was developed to identify patterns in fatalities, including proximal causes, tasks, and contributing factors. This scheme was tested to ensure adequacy of the categories, and fatalities were categorized using the scheme. All testing and categorization were done by two of the authors to ensure reliability of the coding scheme. Results: Patterns were successfully identified to categorize the fatalities, and these patterns were different between coal and metal/nonmetal mines. Coal mines had a greater proportion of electrical-related fatalities, while more fatalities related to potential energy occurred at metal/nonmetal mines. Most of the fatalities were caused by the victim coming into contact with an object or machine or the victim falling from height, and they occurred most often while the victim was performing maintenance or repair on equipment, cleaning, or removing blockages. The most frequent factors contributing to these incidents were failure to properly de-energize or lock out/tag out equipment, violation of work procedures, missing or inadequate safety equipment, and failure to block equipment properly. Conclusions: The classification approach used was successful in identifying hazard patterns during maintenance and repair fatalities in mining. These patterns identify areas to focus attention when developing interventions to prevent the occurrence of future fatalities.

Field assessment of biomechanical and physiological demands in sand and limestone bagging operations

Bagging operations are common in the mining industry and are associated with numerous musculoskeletal injuries. To better understand the physical demands of bagging operations, field evaluations quantifying low back loading and physiological costs of bagging tasks were performed at two bagging operations. A biomechanical model employing electromyography (EMG) and goniometry was used to estimate lumbar compression and a portable metabolic system used to assess heart rate and oxygen consumption. Manual palletizing of bags was found to generate a load of approximately 1,500 Newtons on the spine, with a few larger loads of 2,000-3,000 Newtons. The average oxygen cost for stacking was 5.3 METS, indicating moderately intense physical activity. Bag filling resulted in lower lumbar loads and a reduced physiological cost (3.2 METS), or a moderate level of energy expenditure. Use of a vacuum hoist resulted in a 39% reduction in the peak compressive load on the worker’s spine compared to manual lifting when palletizing 75-lb bags.

Development of ergonomics audits for bagging, haul truck and maintenance and repair operations in mining

Abstract The development and testing of ergonomics and safety audits for small and bulk bag filling, haul truck and maintenance and repair operations in coal preparation and mineral processing plants found at surface mine sites is described. The content for the audits was derived from diverse sources of information on ergonomics and safety deficiencies including: analysis of injury, illness and fatality data and reports; task analysis; empirical laboratory studies of particular tasks; field studies and observations at mine sites; and maintenance records. These diverse sources of information were utilised to establish construct validity of the modular audits that were developed for use by mine safety personnel. User and interrater reliability testing was carried out prior to finalising the audits. The audits can be implemented using downloadable paper versions or with a free mobile NIOSH-developed Android application called ErgoMine. Practitioner Summary: The methodology used to develop ergonomics audits for three types of mining operations is described. Various sources of audit content are compared and contrasted to serve as a guide for developing ergonomics audits for other occupational contexts.

Slip potential for commonly used inclined grated metal walkways

OCCUPATIONAL APPLICATIONS Grated walkway materials are used to discourage accumulation of debris in environments where spillage is likely. Several types of grated walkway materials exist and the choice of walkway material impacts the likelihood of a slip event. In this research, the normalized coefficients of friction were examined for three commonly used grated metal walkways at 0°, 5°, 10°, 15°, and 20°, during both contaminated and dry conditions, and for uphill and downhill walking. Slips were found to occur at inclines as low as 10° from the horizontal, with a high proportion of slips occurring at 20° in the contaminated conditions. The fewest slips occurred during trials for the diamond weave grating. As such, the authors suggest that this grating is preferable for preventing slips, compared to serrated bar or perforated gratings similar to those examined here. TECHNICAL ABSTRACT Background: No specific guidelines or regulations are provided by the Mine Safety and Health Administration for the use of inclined grated metal walkways in mining plants. Mining and other companies may be using walkway materials that do not provide sufficient friction, contributing to slip and fall injuries. Purpose: The purpose of this study was to determine if there are significant differences in the required friction for different grated metal walkways during walking in diverse conditions. Methods: The normalized coefficients of friction were measured for 12 participants while walking up and down an instrumented walkway with different inclinations (0°, 5°, 10°, 15°, and 20°) and with and without the presence of a contaminant (glycerol). Self-reported slip events were recorded and the required coefficients of friction were calculated considering only the anterior/posterior components of the shear forces. Additionally, the available coefficients of friction for these walkway materials were measured at the 0° orientation using a tribometer, with and without the presence of the contaminant, using a boot heel as well as Neolite as the test feet. Results: The number of slips increased when the inclination angle reached 10° and above. Of all materials tested, the diamond weave grating was found to have the best performance at all inclines and when contaminated or dry. A high number of slips occurred for the perforated grating and serrated bar grating at 20° when contaminated. Conclusions: Results of this study suggest that the diamond weave grating provides significantly better friction compared to serrated bar and perforated gratings, especially at inclines greater than 10°.

Inter-Rater Reliability of Video-Based Ergonomic Job Analysis for Maintenance Work in Mineral Processing and Coal Preparation Plants

A large proportion of fatal and non-fatal injuries in mineral processing and coal preparation plants can be attributed to maintenance and repair work. Maintenance work in the mining industry has received little attention due to the challenges associated with collecting and evaluating information on exposures to risk factors and possibly due to the adverse working conditions. The goal of this study was to develop a reliable method to systematically quantify exposures to environmental attributes and physical task demands for maintenance work in mineral processing and coal preparation plants. Hierarchical task analysis was carried out for commonly observed and reported maintenance tasks. A detailed taxonomy of environmental features and physical task demands thought to contribute to injury was created. Two raters independently coded 41 videos using the Multimedia Video Task Analysis™ software to measure the percentage of task time that workers were exposed to each of the variables defined in the taxonomy. For most exposure variables, the mean differences in exposures coded between raters were low and the correlations of exposure durations were high. For variables in which the mean differences in exposure were considered to be too high, modifications to the approach were made to improve measurement reliability. This study provides some evidence to suggest that video based ergonomic job analysis is a viable tool for characterizing the environmental and physical demands of maintenance work in mineral processing and coal preparation plants.