Jonisha P. Pollard

Electromyography of the thigh muscles during lifting tasks in kneeling and squatting postures

Underground coal miners who work in low-seam mines frequently handle materials in kneeling or squatting postures. To assess quadriceps and hamstring muscle demands in these postures, nine participants performed lateral load transfers in kneeling and squatting postures, during which electromyographic (EMG) data were collected. EMG activity was obtained at five points throughout the transfer for three quadriceps muscles and two hamstring muscles from each thigh. ANOVA results indicated that EMG data for nine of 10 thigh muscles were affected by an interaction between posture and angular position of the load lifted (p < 0.001). Muscles of the right thigh were most active during the lifting portion of the task (lifting a block from the participants right) and activity decreased as the block was transferred to the left. Left thigh muscles showed the opposite pattern. EMG activity for the majority of thigh muscles was affected by the size of the base of support provided by different postures, with lower EMG activity observed with a larger base of support and increased activity in postures where base of support was reduced (p < 0.05). Thigh EMG activity was lowest in postures with fully flexed knees, which may explain worker preference for this posture. However, such postures are also associated with increased risk of meniscal damage. Statement of Relevance:Kneeling and squatting postures are sometimes used for manual lifting activities, but are associated with increased knee injury risk. This paper examines the EMG responses of knee extensors/flexors to lifting in these postures, discusses the impact of posture and kneepads on muscle recruitment and explores the implications for work in such postures.

Locomotion in restricted space: kinematic and electromyographic analysis of stoopwalking and crawling.

Stoopwalking and crawling are compulsory gait techniques in some occupational settings, as in low-seam coal mines (where vertical space may be less than 122 cm). Nine participants, six males and three females (mean=35 years+17 SD), participated in a study examining kinematic and electromyographic (EMG) responses to natural cadence stoopwalking, four-point crawling (all fours), and two-point crawling (knees only). EMG data were collected from knee extensors and flexors, and a motion analysis system was used to obtain kinematic data. The average gait velocity for stoopwalking was 1.01 (±0.32)m/s with an average cadence of 112.8 steps/min and stride length of 1.04 m. Four-point crawling velocity averaged 0.50 (±0.20)m/s, with average cadence of 86.3 steps/min and stride length of 0.69m. Two-point crawling exhibited the slowest velocity (0.32m/s) and shortest stride length (0.40 m); however, cadence was greater than four-point crawling (96.8 steps/min). EMG findings included prolonged contraction of both knee extensors and flexors (compared to normative data on normal walking), increased relative activity SD of the flexors (versus extensors) in two-point crawling, and decreased thigh muscle activity in four-point crawling. Interlimb coordination in four-point crawling trials indicated trot-like, no limb pairing, and near pace-like limb contact patterns. Presence or absence of kneepads had no impact on kinematic or EMG measures (p>0.05); however, subjects complained of discomfort without kneepads (especially in two-point crawling). Results of this study have implications for work performed in underground coal mines, as well as emergency or evacuation considerations.

The effect of vibration exposure during haul truck operation on grip strength, touch sensation, and balance

Falls from mobile equipment are reported at surface mine quarry operations each year in considerable numbers. Research shows that a preponderance of falls occur while getting on/off mobile equipment. Contributing factors to the risk of falls include the usage of ladders, exiting onto a slippery surface, and foot or hand slippage. Balance issues may also contribute to fall risks for mobile equipment operators who are exposed to whole-body vibration (WBV). For this reason, the National Institute for Occupational Safety and Health, Office of Mine Safety and Health Research conducted a study at four participating mine sites with seven haul truck operators. The purpose was to ascertain whether WBV and hand-arm vibration (HAV) exposures for quarry haul truck operators were linked to short-term decreases in performance in relation to postural stability, touch sensation threshold, and grip strength that are of crucial importance when getting on/off the trucks. WBV measures of frequency-weighted RMS accelerations (wRMS) and vibration dose value (VDV), when compared to the ISO/ANSI standards, were mostly below levels identified for the Health Guidance Caution Zone (HGCZ), although there were instances where the levels were within and above the specified Exposure Action Value. Comparably, all mean HAV levels, when compared to the ISO/ANSI standards, were below the HGCZ. For the existing conditions and equipment, no significant correlation could be identified between the WBV, HAV, postural stability, touch sensation threshold, and grip strength measures taken during this study.

Using Multiple Complementary Methods to Develop Ergonomics Audits for Mining Operations

Although ergonomics audits are commonly used by consultants, the scientific literature on reliable and valid audits is sparse. This paper describes a multi-faceted methodological approach to developing ergonomics audits for three types of mining operations. The approach was derived from a validated audit (Ergonomics Assessment Program (ERNAP)) for aircraft maintenance operations. While there were contextual, regulatory, and intended end user differences, the general approach to establishing content validity through task analysis and workplace observations, surveillance data, and accepted practices and regulations proved to be effective, albeit with modifications. Analysis of fatality reports and desire for integration with existing mining safety approaches were two areas where the current approach differed from ERNAP.

The effect of kneepads on balance while kneeling or squatting

In all industries, maintaining balance is essential to ensure that workers can safely perform their job duties. In low-seam underground coal mines, workers perform their duties while kneeling, squatting, and crawling with kneepads. In this study, researchers examined the effects of kneeling and squatting on balance measures under the right knee (for kneeling) and right foot (for squatting) with and without kneepads. Results showed that kneepads did not significantly affect balance. Posture had a significant effect on balance measures, with squatting postures showing reduced balance compared to the kneeling postures. For the kneeling postures, ground force measurements were also correlated to balance measures. Posterior tibial forces were shown to have the greatest correlation to mediolateral and anteroposterior average velocities. Force and balance measures highlight a compromise between loading and balance, where improved balance is achieved with increased knee loading.

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.

Off-road truck-related accidents in U.S. mines

INTRODUCTION Off-road trucks are one of the major sources of equipment-related accidents in the U.S. mining industries. A systematic analysis of all off-road truck-related accidents, injuries, and illnesses, which are reported and published by the Mine Safety and Health Administration (MSHA), is expected to provide practical insights for identifying the accident patterns and trends in the available raw database. Therefore, appropriate safety management measures can be administered and implemented based on these accident patterns/trends. METHODS A hybrid clustering-classification methodology using K-means clustering and gene expression programming (GEP) is proposed for the analysis of severe and non-severe off-road truck-related injuries at U.S. mines. Using the GEP sub-model, a small subset of the 36 recorded attributes was found to be correlated to the severity level. RESULTS Given the set of specified attributes, the clustering sub-model was able to cluster the accident records into 5 distinct groups. For instance, the first cluster contained accidents related to minerals processing mills and coal preparation plants (91%). More than two-thirds of the victims in this cluster had less than 5years of job experience. This cluster was associated with the highest percentage of severe injuries (22 severe accidents, 3.4%). Almost 50% of all accidents in this cluster occurred at stone operations. Similarly, the other four clusters were characterized to highlight important patterns that can be used to determine areas of focus for safety initiatives. CONCLUSIONS The identified clusters of accidents may play a vital role in the prevention of severe injuries in mining. Further research into the cluster attributes and identified patterns will be necessary to determine how these factors can be mitigated to reduce the risk of severe injuries. PRACTICAL APPLICATION Analyzing injury data using data mining techniques provides some insight into attributes that are associated with high accuracies for predicting injury severity.