Gerard A. Davis

Effects of ventilated safety helmets in a hot environment

Forest workers are likely to remove head protection in hot and humid conditions because of thermal discomfort. However, a recent Occupational Safety and Health Administration (OSHA) regulation revision requires all workers in logging operations to wear safety helmets, thus creating a compliance problem. To determine which factors contribute to forest workers’ thermal discomfort, this study evaluated subjects’ physiological and psychophysical responses during tasks approximating the workload of forest workers in a high-temperature environment similar to that found in the southeastern United States during the summer. Environmental conditions in the helmet dome space were also evaluated. Three helmets were used in this study: a standard helmet, a passively ventilated helmet, and an actively ventilated helmet. It was found that none of the tested helmets burdened the body significantly for the physiological variables that were examined. Evaluation of the dome space environmental conditions showed that both the dry-bulb temperature (DBT) and wet-bulb temperature (WBT) varied significantly among the helmets tested. Psychophysical results showed that ventilation contributes to greater helmet comfort, and that weight and fit are important factors in helmet design. Relevance to industry Protective helmets for use in hot and humid environments should be modified to make them more comfortable, encouraging forest workers to wear them and thus comply with OSHA regulations. # 2001 Elsevier Science B.V. All rights reserved.

Morphometry of the lower lumbar intervertebral discs and endplates: comparative analyses of new MRI data with previous findings

PurposeVariability of the human lower lumbar geometry is related to complications of disc arthroplasty surgery. Accurate morphometric descriptions are essential for the design of artificial intervertebral discs to ensure good prothesis-vertebra contact and better load distribution, and can improve spinal biomechanics. Unfortunately, current knowledge of the lower lumbar geometry is limited either in the representativeness of sample populations or the accuracy and comprehensiveness of measurements. The objective of this study was to establish an accurate and reliable measurement protocol, provide a comprehensive database of lower lumbar geometry, and compare and summarize geometric data as reported in the literature.MethodsT2-weighted magnetic resonance imaging (MRI) scans of lower lumbar spine (L3–S1), taken from 109 adult subjects, were anonymized from the digital archive of a local hospital. A total of 318 intervertebral discs and 590 endplates met the inclusion criteria and were studied. Linear and planar measurements were performed using OsiriX software, and analyzed using split plot factorial (SPF) analysis of variance (ANOVA), independent student t tests, paired sample t tests, and Tukey’s honest significant difference (HSD) post hoc tests.ResultsExcellent intra- and inter-observer reliabilities were achieved using the proposed measurement protocol. The results of this study indicated that male subjects had significantly larger geometric dimensions. L5/S1 discs had the smallest geometric dimensions compared to the discs at other two levels. Significant craniocaudal differences were found in endplate morpohometry. The error associated with using ellipsoid methods was quantified at each lower lumbar level. A large comprehensive database compiling lower lumbar geometry from many studies was established. This study provides geometric data for the female subjects at the L5/S1 level, previously lacking in the literature.ConclusionThis study demonstrates the potential of using MRI data to establish a standard measurement protocol for morphometric quantification of the lower lumbar intervertebral discs and vertebral endplates. These results are invaluable in characterizing comprehensive lower lumbar morphometry, which may provide crucial information for planning spinal surgeries, designing artificial intervertebral discs, and for biomechanical modeling of the low lack.

Improving the risk assessment capability of the revised NIOSH lifting equation by incorporating personal characteristics

The impact of manual material handling such as lifting, lowering, pushing, pulling and awkward postures have been studied, and models using these external demands to assess risk of injury have been developed and employed by safety and health professionals. However, ergonomic models incorporating personal characteristics into a comprehensive model are lacking. This study explores the utility of adding personal characteristics such as the estimated L5/S1 Intervertebral Disc (IVD) cross-sectional area, age, gender and Body Mass Index to the Revised NIOSH Lifting Equation (RNLE) with the goal to improve risk assessment. A dataset with known RNLE Cumulative Lifting Indices (CLIs) and related health outcomes was used to evaluate the impact of personal characteristics on RNLE performance. The dataset included 29 cases and 101 controls selected from a cohort of 1022 subjects performing 667 jobs. RNLE risk assessment was improved by incorporation of personal characteristics. Adding gender and intervertebral disc size multipliers to the RNLE raised the odds ratio for a CLI of 3.0 from 6.71 (CI: 2.2-20.9) to 24.75 (CI: 2.8-215.4). Similarly, performance was either unchanged or improved when some existing multipliers were removed. The most promising RNLE change involved incorporation of a multiplier based on the estimated IVD cross-sectional area (CSA). Results are promising, but confidence intervals are broad and additional, prospective research is warranted to validate findings.

Evaluating the Linear Integration Method of Estimating Cumulative Loading Using an Eccentric Exercise

The ability to quantify cumulative exposure is critically in understanding dose-response relationship in the development of work-related musculoskeletal disorders. Different integration methods have been used in estimating cumulative loading (force or torque). The general objective of cumulative loading integration methods has been to sum the loading exposure for each individual task, calculate by multiplying the magnitude of the task loading times the task duration, and develop an “area under the curve”. An assumption of this linear integration model is that short time exposure to high forces will result in a similar level of damage as relatively long-time exposure to low forces. In this study, three loading groups of eccentric exercise with the same “area under the curve” were performed by thirty participants (ten in each group). Relaxed elbow angle and maximum isometric voluntary contractions (MIVC) were collected before, immediately after, and 2, 4, 8 days after the exercise. The relaxed elbow angle and the changes in MIVC were significantly impacted by the loading group. This result suggests that the linear integration method of estimating cumulative loading may underestimate the impact of high force loading in terms of cumulative muscle damage.

Lumbar Muscle Fatigue Analysis Using Sorensen Test with Different Upper Body Offload Conditions

The Sorensen test has been widely used in assessing the isometric endurance of trunk muscles. In this study, a modified Sorensen test was performed using four different upper body offload conditions (0%, 25% 50% and 75%) and surface EMG (sEMG) was used to determine fatigue characteristics in lumbar muscles. Results showed that the offloading of the upper body has a statistically significant impact on the slope of the EMG median frequency, which is representative of lumbar muscle fatigue responses. The first 25% offloading significantly decreased the fatigue response in the lumbar region. In addition, the 25% offload condition was significantly different from the 75% offload condition. However, the slopes of 25% and 50% offload conditions are not statistically different from each other and same for 50% and 75% offload conditions.

Effectiveness of Pictogram Instructions for Donning Smoke Hoods

Smoke hoods or respiratory protective emergency devices (RPEDs) are marketed to assist in evacuation from fire emergencies. Many smoke hood manufacturers often rely on pictograms to instruct proper donning procedures to smoke hood users. Comprehending the instructions delivered through pictograms plays an important role in properly donning a smoke hood, and avoiding further injuries or complications from improper usage of the smoke hood. The purpose of this study was to determine the effectiveness of pictogram instructions used by three types of smoke hoods for donning a smoke hood. Results of this study indicate that the type of pictogram instructions have a significant effect on the ability of a user to properly don a smoke hood. While detailed pictogram instructions help users properly don smoke hoods, they also have an impact on the time required to don a smoke hood.

Heart Rate and Perceived Exertion Among Young Adult Obese Males During One-Handed Carrying

Obesity is an increasing problem across the globe that has been strongly associated with work-related injury. One-handed carrying is considered one of the most fatiguing methods of load carrying. The objective of this study was to examine the effects of obesity and load magnitude on heart rate and ratings of perceived exertion among young adult males during one-handed carrying. Load magnitude was observed to have a statistically significantly effect on heart rate and perceived exertion of the arm, back and whole body, whereas obesity was significant only for perceived exertion of the arm. The results suggest that young adult obese males can carry similar loads as young adult non-obese males without having a statistically significant increase in heart rate or perceived exertion. However, more research is needed to validate these results for longer distances and carrying times.

Evaluating an Inertial Measurement Unit Based System for After-Reach Speed Measurement in Power Press Applications

The objective of this study was to measure the hand speed of eighteen (18) subjects making after-reach movements from an upper palm button (UB) and lower palm button (LB) on a simulated press. Each after-reach movement was measured with a Vicon optical motion capture system and an Xsens IMU based system. A Bland-Altman analysis of the speed measured by the two technologies demonstrated a general agreement (average bias 0.19 m/s) between the measurements and a potential for using IMUs for hand-speed measures in the future. However, the computation intensity required to manipulate the Xsens data is likely too complex and time consuming for practitioners who are busy with plant activities. A simple IMU system, designed specifically for hand speed capture, could be a viable option for measuring after-reach speed in the future.

One-handed carrying among elderly and obese individuals: A systematic review to identify research gaps

Abstract A systematic review of the literature regarding one-handed load carrying was conducted to identify research gaps for future load carrying studies. Twenty-six articles that may be relevant to elderly and obese people were included. Only two studies evaluated the effect of age as an independent variable during one-handed carrying. Obesity was not included as an independent variable in any of the articles. In general, the results suggested that one-handed carrying is more physically demanding than other methods of load carrying. In many cases, physiological responses to carrying a load in one hand were similar to carrying twice the load equally distributed between two hands. Some studies recommended a one-handed carrying weight limit of approximately 9–10 kg for men and 6–7 kg for women. However, more research on the effects of age and obesity during one-handed carrying is needed to determine if these results hold for elderly and obese people. Practitioner Summary: A systematic review of the scientific literature since 1966 regarding one-handed carrying that may pertain to elderly and/or obese people was performed. Few studies were identified that included aging and none included obesity as independent variables. Areas for future research are identified and discussed.

Can the Revised NIOSH Lifting Equation Be Improved by Incorporating Personal Characteristics

The impact of manual material handling such as lifting, lowering, pushing and pulling have been extensively studied. Many models using these external demands to predict injury have been proposed and employed by safety and health professionals. However, ergonomic models incorporating personal characteristics into a comprehensive model are lacking. This study explores the utility of adding personal characteristics such as the estimated L5/S1 Intervertebral Disc (IVD) cross sectional area, height, age, gender and Body Mass Index (BMI) to the Revised NIOSH Lifting Equation (RNLE) with the goal to improve injury prediction. A dataset with known RNLE Cumulative Lifting Indices (CLIs) and related health outcomes was used to evaluate the impact of personal characteristics on RNLE performance. The dataset included 29 cases and 101 controls selected from a cohort of 1,022 subjects performing 667 jobs. RNLE performance was significantly improved by incorporation of personal characteristics. Adding gender and intervertebral disc size multipliers to the RNLE raised the odds ratio for a CLI of 3.0 from 6.71 (CI: 2.2–20.9, PPV: 0.60, NPV: 0.82) to 24.75 (CI: 2.8–215.4, PPV: 0.86, NPV: 0.80). The most promising RNLE change involved incorporation of the multiplier based on the estimated IVD cross-sectional area (CSA). This multiplier was developed by normalizing against the IVD CSA for a 50th percentile woman. This multiplier could assume values greater than one (for subjects with larger IVD CSA than a 50th percentile woman). Thus, CLI could both decrease and increase as a result of this multiplier. Increases in RNLE performance were achieved primarily by decreasing the number of RNLE false positives (e.g., some CLIs for uninjured subjects were reduced below 3.0). Results are promising, but confidence intervals are broad and additional, prospective research is warranted to validate findings.