The Strain Index was originally designed to analyze mono-task jobs. An experiment using a grip dynamometer was used to simulate six multiple task jobs to study the effect of complex tasks on localized muscle fatigue and to evaluate six different models used to calcula te a Complex Strain Index score. These models included average Strain Index score, unadjusted summation, duration adjusted summation, complex equation, minimum intensity, and peak intensity. Two methods of calculating a continuous Strain Index score were also analyzed. Ratings of perceived exertion, hand and forearm fatigue and discomfort, Difficulty Rating, maximum voluntary contraction (MVC), and percent strength loss were recorded for each of the six treatments. Electromyography (EMG) was also recorded for the 24 subjects (12 males and females) who completed the experiment. The EMG signal was analyzed using root mean square (RMS), initial mean power frequency (IMnPF), and slope of the mean power frequency (MnPF). Each treatment, lasting one hour each, contained a primary exertion (Task 1) of either 10% or 40% MVC for three seconds and a secondary exertion (Task 2) of either 10% or 40% MVC for one or three seconds. Subjective variables linearly increased (R2 > 0.88) over the duration of the treatments and significantly differed between treatments (p < 0.05). Percent strength loss was the only variable with a gender effect (p < 0.05). RMS values did not indicate fatigue and were constant over each treatment, but were highly correlated with percent MVC. A significant difference was not found in IMnPF between pre and post treatment values or between treatments (p > 0.05). A significant difference was found for MnPF slope pre and post treatment, but no treatment effect was found (p > 0.05). The complex equation method of calculating a Strain Index score was the only model of the six evaluated that met all criteria for being an acceptable method of calculating a Complex Strain Index score. The two continuous methods presented for calculating a Strain Index score should not be used for job analysis until further research evaluates their reliability, validity, and critical scores for Hazard Classification.

The Strain Index (SI) has repeatedly shown high levels of validity for differentiating between safe and hazardous tasks for the distal upper extremity (DUE). One limitation of the SI is the lack of reliability data. This study was designed to evaluate the test-retest repeatability of the SI. Fifteen raters, divided into five teams of three, were asked to use the SI to analyze 73 video AVI files of different job tasks; initially as individuals and then as teams. Several months later, raters were asked to repeat individual and team job task assessments. Raters were instructed to analyze tasks using five of six SI task variables, while the sixth was held constant. For three of these task variables, additional data was collected such as peak force and duration of job cycle. Test-retest repeatability was measured using Pearson's R, Spearman's rho, and tetrachoric correlation according to the nature of the variable. Spearman's rho values for individual and team task variable ratings ranged from 0.68 to 0.96 (0.88 average). Pearson's R for task variable data ranged from 0.76 to 0.99 for both teams and individuals with an average of 0.91. The Strain Index's rho values for individuals and teams were 0.70 and 0.84, respectively. For hazard classification, the tetrachoric correlation for individuals was 0.81 and 0.88 for teams. Results of this study support the conclusion that the Strain Index is repeatable when used by teams as well as individuals.

The Strain Index (SI) has repeatedly shown high levels of validity for differentiating between safe and hazardous tasks for the distal upper extremity (DUE). One limitation of the SI is the lack of reliability data. This study was designed to evaluate the test-retest repeatability of the SI. Fifteen raters, divided into five teams of three, were asked to use the SI to analyze 73 video AVI files of different job tasks; initially as individuals and then as teams. Several months later, raters were asked to repeat individual and team job task assessments. Raters were instructed to analyze tasks using five of six SI task variables, while the sixth was held constant. For three of these task variables, additional data was collected such as peak force and duration of job cycle. Test-retest repeatability was measured using Pearson's R, Spearman's rho, and tetrachoric correlation according to the nature of the variable. Spearman's rho values for individual and team task variable ratings ranged from 0.68 to 0.96 (0.88 average). Pearson's R for task variable data ranged from 0.76 to 0.99 for both teams and individuals with an average of 0.91. The Strain Index's rho values for individuals and teams were 0.70 and 0.84, respectively. For hazard classification, the tetrachoric correlation for individuals was 0.81 and 0.88 for teams. Results of this study support the conclusion that the Strain Index is repeatable when used by teams as well as individuals.

O presente trabalho teve como objetivo estudar a comparação entre o protocolo de Couto e o protocolo Strain Index, de Moore e Garg, para Análise Ergonômica do Trabalho, em dois postos de tornearia do setor de usinagem de uma indústria de médio porte, do setor metalúrgico. Para tanto, realizou-se uma fundamentação teórica, para apresentação dos métodos, cujos protocolos não são equivalentes (embora sejam aplicados como tal). Foi uma pesquisa aplicada, cujos resultados foram submetidos à análise quantitativa, buscando verificar os mecanismos de lesão a que estão sujeitos os operadores de tornos, neste caso específico, de uma indústria metalúrgica que possui dois postos de tornearia, sendo um para peças maiores que necessitam do uso de dispositivos de içamento e o outro posto dedicado a peças menores, capazes de serem manuseadas pelo operador. Concluiu-se que a relação entre o trabalho e a saúde requer a implantação e implementação, por parte das organizações e de políticas de prevenção, construindo uma cultura organizacional, em que seja propícia a realização da missão da organização com a garantia da qualidade de vida e realização das pessoas. / This study aimed to study the comparison between the protocol and the protocol Couto Strain Index, Moore and Garg, for ergonomic work analysis in two positions in the industry turning the machining of a medium-sized industry, metallurgical industry. To this end, we carried out a theoretical basis for presentation of methods, protocols are not equivalent (although they are applied as such). It was an applied research, whose results were submitted to quantitative analysis, in order to understand the mechanisms of injury that are subject to the operators of lathes in this particular case, a metal industry, which has two turning stations, one for larger parts that need the use of lifting devices and other station dedicated to smaller parts, capable of being handled by the operator. It was concluded that the relationship between work and health requires the establishment and implementation by organizations and prevention policies, building an organizational culture that is conducive to achieving the mission of the organization with the guarantee of quality of life and fulfillment of people.

Protective clothing ensembles are worn by workers as a barrier to chemical and physical hazards, but can restrict heat loss and increase worker heat stress. The question of whether a respirator adds to heat stress or strain burden is a continuing concern among occupational health professionals. The purpose of this study was to determine if there are differences in heat stress or strain among the current Toxicological Agent Protective (TAP) ensemble and two ensemble variations used in demilitarization of chemical weapons. Four acclimatized adult males wore five ensembles in a balanced design while walking in a climatic chamber at a metabolic rate of about 170 W m-2. Heat stress (critical wet bulb globe temperature-WBGTcrit, evaporative resistance-Re,T,a, Clothing Adjustment Factor [CAF]) and heat strain (physiological strain index [PSI]) were compared against work clothes (WC) without respirator (a baseline ensemble); the current TAP apron over cloth coveralls with respirator (TAP+CA); the current TAP apron over cloth coveralls with respirator plus Tychem F® chemical barrier pants (TAP+CA+P); and Tychem F® Coveralls over cloth coveralls with respirator (VB+CA). A no-respirator comparison with the Tychem F coveralls (VB+CA-noR) was added to evaluate the contribution of a full-face negative pressure air-purifying respirator to heat stress. A progressive heat stress protocol was used to determine WBGTcrit, Re,T,a, CAF, and PSI. The results (WBGTcrit [°C-WBGT], Re,T,a [kPa m2 W-1], and PSI) were WC (35.5, 0.0112, 2.0), TAP (31.6, 0.0175, 1.8), TAP+P (27.7, 0.0240, 1.9), VB+CA (25.9, 0.0287, 1.8), and VB+CA-noR (26.2, 0.0293, 1.8). Mixed effects ANOVA was used to assess ensemble effects. Tukey's test was used to determine where significant differences occurred. WBGTcrit was the WBGT at the upper limit of thermal balance. Re,T,a increased while WBGTcrit progressively decreased going from WC to TAP+CA to TAP+CA+P to VB+CA. WBGTcrit was different between Work Clothes and TAP+CA and between WC and TAP+CA and the other ensembles. Re,T,a was different among all ensembles, except no differences in WBGTcrit and Re,T,a were observed between the presence and absence of a respirator with VB+CA. There were no differences among all ensembles for rectal temperature, heart rate, and PSI. Based on both WBGTcrit and Re,T,a, there were significant increases in heat stress going from WC to TAP+CA to TAP+CA+P to VB+CA. No differences in WBGTcrit, Re,T,a, and PSI were found for the presence or absence of a respirator, indicating no additional heat stress or strain burden. CAF is the WC WBGTcrit minus the ensemble WBGTcrit.. The recommended clothing adjustment factors (CAFs) are 0°C-WBGT for WC, 4 °C-WBGT for TAP+CA, 8 °C-WBGT for TAP+CA+P and 10 °C-WBGT for VB+CA. As vapor-barrier ensembles are sensitive to humidity, adding 2 °C-WBGT to VA+CA for a CAF of 12 °C-WBGT is recommended. This implicates the type of protective clothing ensemble worn will play a much bigger role in workplace heat stress effects and risk than the wear of a respirator.

Work-related musculoskeletal disorders (MSDs) account for more than 350,000 occupational illnesses and injuries in the United States. Many job risk factors for developing MSDs are found in the automotive industry and the United Automobile Workers (UAW)-Ford Ergonomics Surveillance Tool (EST) has been designed to screen these jobs into high, moderate or low risk for work-related musculoskeletal disorders affecting the distal upper extremity (DUE), lower back (LB) and/or neck and shoulders (NS). The purpose of this effort was to examine the predictive validity of the EST against a sample of target jobs at four Ford plants. Individual jobs for this study were selected by a stratified random assignment. Health records from Ford were reviewed in order to identify first time office visits (FTOVs), which were symptomatic complaints made by individual workers. Jobs that were associated with FTOVs were defined as case jobs for the three body regions. These case jobs were compared with predictions for injury by EST. Sensitivity and specificity were used to test predictive validity. While the sensitivity was poor for all body regions tested, the specificities were fairly strong for DUE and NS when looking at low risk compared to moderate/high risk. The low risk DUE specificity was 0.67 and increased to 0.78 when looking at low/moderate risk compared to high. Low back specificity for low risk was 0.51 but increased to 0.85 when looking at low/moderate risk compared to high. The NS specificity score was 0.81, increasing to 0.85 when looking at low/moderate risk. While the EST does not predict which jobs are high risk for injury, it does screen out safe jobs. Therefore, jobs identified by the EST as low/moderate risk are likely to be safe.

Assessment of heat strain considers an individual's tolerance and indicates the risk and physiological cost of working in hot environments. This study evaluated the discrimination ability of metrics of heat strain. The null hypotheses were that (1) the metrics individually could not discriminate between acceptable and unacceptable heat strain, (2) there were no significant differences among these metrics, and (3) there were no significant differences in the applicability of the metrics due to clothing or heat stress level. The experimental design was a case crossover. Clothing and heat stress level were potential confounders. Two clothing ensembles were work clothes and vapor-barrier coveralls with hood. Two heat stress levels for a moderate metabolic rate were 5°C-WBGT and 10°C-WBGT above the Threshold Limit Value adjusted for clothing. Eight male and four female acclimated individuals (age 18-36 years) participated. Four experimental trials were randomized in sequence. The transition point, when a participant's status changed from control (acceptable heat strain) to case (unacceptable), was the first occurrence of rectal temperature equal to or greater than 38.5°C, heart rate equal to or greater than 90% of maximum, or volitional fatigue. The metrics were rectal, ear canal, oral, and disk temperatures, heart rate including moving time averages of 5, 10, 20, 30 and 45 minutes, recovery heart rate, and physiological strain index. The data at the transition point were the case data; the data 10 minutes prior to that point were the control data. Analyses used primarily receiver operating characteristic (ROC) curves, which indicated the ability to distinguish acceptable from unacceptable heat strain. Further analyses included factorial analysis of variance and exact conditional logistic regression. Based on the ROC curve analyses, the physiological metrics can distinguish between acceptable and unacceptable heat strain with average area under the curves between 0.529 and 0.861. While there were no differences among the metrics based on the 95% confidence intervals of the areas under the curve, the results were compromised by low power. Based on ANOVA and logistic regression, clothing did not influence the metrics. There were insufficient data to evaluate the role of heat stress level.

Ebola, a type of filovirus that causes hemorrhagic fevers, dominated global headlines in 2014 when the largest Ebola epidemic in history took place in West Africa. Healthcare practitioners were at particular risk of contracting Ebola while taking care of patients with the disease because they were easily exposed to bodily fluids such as blood, urine, saliva, and feces, quite often in the intensive care unit (ICU). While personal protective equipment (PPE) protects the healthcare practitioner by providing an effective barrier against the virus, users were also at risk for heat stress because of the type of protective clothing. In this study, coveralls made of monolithic barriers, which prevent water vapor from escaping the suit, were compared to coveralls made of micro- porous material, which allows evaporated sweat to escape the suit. The Microgard® 2000 TS Plus, made of micro-porous barrier material and the monolithic barrier Microgard® 2300 Plus were compared against a control ensemble of work clothes consisting of a long-sleeve shirt and trouser. A progressive heat stress protocol was used to determine the critical environment at the upper limit of compensable heat stress. The critical condition was the point at which the heat gain caused by wearing the protective ensemble as well as dry heat exchange was balanced by the maximum heat loss due to evaporative cooling. Wet bulb globe temperature at the critical condition (WBGTcrit ) ,total evaporative resistance (Re,T,a), and clothing adjustable factor (CAF) were calculated for each ensemble based on data at the critical point. Also at the critical condition, participant rectal temperature vi (Tre) , heart rate (HR), skin temperature (Tsk), and physiological strain index (PSI) were noted and compared for each ensemble. A two-way ANOVA (ensemble x participant) for WBGTcrit and Re,T,a as dependent variables was used to determine whether or not there were differences among ensembles. Tukey’s honest significance test was used to determine where significant differences occurred. WBGTcrit was 33.8, 26.3, and 22.9 °C-WBGT for Work Clothes, M2000, and M2300 respectively. Re,T,a was 0.012, 0.031, and 0.054 kPa m2 W-1 for WC, M2000, and M2300 respectively. The higher the WBGTcrit for an ensemble, the more it can support evaporative cooling and hence the better it is at ameliorating heat stress. Based on this trial, the micro-porous ensemble Microgard® 2000 TS Plus has better heat stress performance than vapor-barrier Microgard® 2300 Plus. As expected, there were no differences for any of the physiological metrics at the critical conditions.