The Revised Strain Index (RSI), despite its prevalence in ergonomics field practice, is designed to assess jobs with cyclic and predictable physical and behavioral patterns. The quantification of exertion force, posture, and work task duration is substantially more challenging for non-routinized work in clinical and hospital environments. Using dental hygiene work as an exemplar, we proposed a consolidated method to characterize physical exertion for non-routinized work. We conducted the RSI adaptation process in two phases. In phase one, we characterized exertion in non-routinized work and identified representative intensity and posture patterns. In phase two, we validated the consolidated method using a small subset of dental hygiene video recordings and compared the results to the conventional sampling method.

In a previous study, an unexpected u-shaped relationship was observed between load level and fatigue/recovery responses. Moderate load levels resulted in lower perceived discomfort, pain, and fatigue, and shorter recovery times compared to either low or high load levels. This phenomenon has been reported in other studies, but no article has examined the possible mechanisms that might explain this u-shaped relationship. In this paper, we re-examined the previously published data and found that the phenomenon does not appear to be due to the experimental artefact; the u-shape may be due to unexpectedly lower fatigue effects at moderate loads, and higher fatigue effects at lower loads. We then conducted a literature review and identified several possible physiological, perceptual, and biomechanical explanatory mechanisms. No single mechanism explains the entirety of the phenomenon. Further research is needed on the relationship between work exposures, fatigue, and recovery, and the mechanisms related to the u-shaped relationship.Practitioner summary: We examine a previously observed u-shaped relationship between load level and fatigue/recovery, where moderate force resulted in lower perceived fatigue and shorter recovery times. A u-shaped fatigue response suggests that simply minimising load levels might not be an optimal approach to reduce the risk of workplace injuries.

OBJECTIVE:The aim of the study is to assess risk of common musculoskeletal disorders (MSDs) based on cardiovascular disease (CVD) risk scores.METHODS:Data from a 9-year prospective cohort of 1224 workers in three states were analyzed. Baseline data included questionnaires, structured interviews, physical examinations, anthropometric measurements, nerve conduction studies, and individualized measurement of job physical factors. Monthly follow-ups were conducted. Framingham risk scores were calculated. A priori case definitions were constructed for carpal tunnel syndrome, lateral epicondylopathy, medial epicondylopathy, and rotator cuff tendinopathy.RESULTS:Adjusted RRs for one or more MSDs increased to 3.90 (95% confidence interval, 2.20-6.90) among those with 10-year cardiovascular disease risk scores greater than 15% and 17.4 (95% confidence interval, 3.85-78.62) among those with more than 4 disorders.CONCLUSIONS:Cardiovascular disease factors are strongly associated with the subsequent development of common MSDs. Risks among those with multiple MSDs are considerably stronger.

BACKGROUND:Although recent studies have identified important risk factors associated with incident carpal tunnel syndrome (CTS), risk factors associated with its severity have not been well explored. OBJECTIVE:To examine the associations between personal, workplace psychosocial and biomechanical factors and incident work disability among workers with CTS. METHODS:Between 2001 and 2010 five research groups conducted coordinated prospective studies of CTS and related work disability among US workers from various industries. Workers with prevalent or incident CTS (N=372) were followed for up to 6.4 years. Incident work disability was measured as: (1) change in work pace or work quality, (2) lost time or (3) job change following the development of CTS. Psychosocial factors were assessed by questionnaire. Biomechanical exposures were assessed by observation and measurements and included force, repetition, duty cycle and posture. HRs were estimated using Cox models. RESULTS:Disability incidence rates per 100 person-years were 33.2 for changes in work pace or quality, 16.3 for lost time and 20.0 for job change. There was a near doubling of risk for job change among those in the upper tertile of the Hand Activity Level Scale (HR 2.17; 95% CI 1.17 to 4.01), total repetition rate (HR 1.75; 95% CI 1.02 to 3.02), % time spent in all hand exertions (HR 2.20; 95% CI 1.21 to 4.01) and a sixfold increase for high job strain. Sensitivity analyses indicated attenuation due to inclusion of the prevalent CTS cases. CONCLUSION:Personal, biomechanical and psychosocial job factors predicted CTS-related disability. Results suggest that prevention of severe disability requires a reduction of both biomechanical and organisational work stressors.

Objective To examine differences in demographic, psychosocial, and job physical exposure risk factors between multiple low back pain (LBP) outcomes in a prospective cohort of industrial workers. Background LBP remains a leading cause of lost industrial productivity. Different case definitions involving pain (general LBP), medication use (M-LBP), seeking healthcare (H-LBP), and lost time (L-LBP) are often used to study LBP outcomes. However, the relationship between these outcomes remains unclear. Method Demographic, health status, psychosocial, and job physical exposure risk factors were quantified for 635 incident-eligible industrial workers. Incident cases of LBP outcomes and pain symptoms were quantified and compared across the four outcomes. Results Differences in age, gender, medical history, and LBP history were found between the four outcomes. Most incident-eligible workers (67%) suffered an LBP outcome during follow-up. Cases decreased from 420 for LBP (25.4 cases/100 person-years) to 303 for M-LBP (22.0 cases/100 person-years), to 151 for H-LBP (15.6 cases/100 person-years), and finally to 56 for L-LBP (8.7 cases/100 person-years). Conversely, pain intensity and duration increased from LBP to H-LBP. However, pain duration was relatively lower for L-LBP than for H-LBP. Conclusion Patterns of cases, pain intensity, and pain duration suggest the influence of the four outcomes. However, few differences in apparent risk factors were observed between the outcomes. Further research is needed to establish consistent case definitions. Application Knowledge of patterns between different LBP outcomes can improve interpretation of research and guide future research and intervention studies in industry.

Background: The objective of this study was to investigate the prevalence of carpal tunnel syndrome (CTS) in workers with trigger digit. There are few cross-sectional studies that assess this relationship. Methods: A baseline examination of 1216 workers from 17 diverse manufacturing facilities was conducted. Worker demographics, medical history, and symptoms of trigger digit were assessed. Age, sex, and body mass index were obtained. Biomechanical factors were individually measured using the Strain Index (SI). Prevalence was assessed with univariate and multivariate logistic regression. Results: Unadjusted prevalence of trigger digit was 12.0%, and among those workers, there was an unadjusted CTS prevalence of 26.7%. The adjusted multivariate model found an odds ratio (OR) of CTS of 1.56 (95% confidence interval [CI], 1.03-2.36) among the workers with trigger digit. The ORs of CTS for SI (OR = 1.53 [95% CI, 1.04-2.23]), age (OR = 1.03 [95% CI, 1.01-1.04]), and current smoking (OR = 1.76 [95% CI, 1.12-2.75]) were also significant. Sex and diabetes were not statistically significant covariates. Conclusion: The prevalence of CTS is higher among workers with trigger digit.

Background. Cholesterol levels in total cholesterol (TC), low-density lipoprotein (LDL-C), high-density lipoprotein (HDL-C), and triglyceride (TG) contribute to atherosclerosis and its clinical consequences. Objectives. This study aimed to examine the trends in serum TC/HDL and LDL/HDL ratio across the age span. Methods. This is an observational study. Blood lipid measurements, taken from 85,646 noninstitutionalized participants, aged 6 to 80, were obtained from the National Health and Nutrition Examination Survey (NHANES) study. We compared the TC/HDL and LDL/HDL ratio trends in three distinct cross-sectional surveys during 2007-2010, 2011-2014, and 2015- 2018. Results. Cholesterol ratios changed by age and differed by sex. Mean TC/HDL ratios declined from 4.03 (95% CI, 4.01-4.05) in 2007-2010, to 3.84 (95% CI, 3.81-3.87) in 2015-2018 (p<.05 for linear trend) in male; mean TC/HDL ratios declined from 3.69 (95% CI, 3.67-3.70) in 2007- 2010, to 3.45 (95% CI, 3.42-3.47) in 2015-2018 (p<.05 for linear trend) in female. Mean LDL/HDL ratios declined from 2.30 (95% CI, 2.28-2.32) in 2007-2010, to 2.18 (95% CI, 2.15- 2.20) in 2015-2018 (p<.05 for linear trend) in male; mean LDL/HDL ratios declined from 2.04 (95% CI, 2.02-2.06) in 2007-2010, to 1.96 (95% CI, 1.94-1.98) in 2015-2018 (p<.001 for linear trend) in female. Conclusions. Between 2007 and 2018, favorable trends in lipid ratio levels were observed among noninstitutionalized residents in the US.

Objective The purpose of this study was to develop an approach to predict hand posture (pinch versus grip) and grasp force using forearm surface electromyography (sEMG) and artificial neural networks (ANNs) during tasks that varied repetition rate and duty cycle. Background Prior studies have used electromyography with machine learning models to predict grip force but relatively few studies have assessed whether both hand posture and force can be predicted, particularly at varying levels of duty cycle and repetition rate. Method Fourteen individuals participated in this experiment. sEMG data for five forearm muscles and force output data were collected. Calibration data (25, 50, 75, 100% of maximum voluntary contraction (MVC)) were used to train ANN models to predict hand posture (pinch versus grip) and force magnitude while performing tasks that varied load, repetition rate, and duty cycle. Results Across all participants, overall hand posture prediction accuracy was 79% (0.79 ± .08), whereas overall hand force prediction accuracy was 73% (0.73 ± .09). Accuracy ranged between 0.65 and 0.93 based on varying repetition rate and duty cycle. Conclusion Hand posture and force prediction were possible using sEMG and ANNs, though there were important differences in the accuracy of predictions based on task characteristics including duty cycle and repetition rate. Application The results of this study could be applied to the development of a dosimeter used for distal upper extremity biomechanical exposure measurement, risk assessment, job (re)design, and return to work programs.

Abstract The Revised Strain Index (RSI), a model that quantifies physical exposure from individual hand/wrist exertions, tasks, and multi-task jobs, was used to quantify exposure for 1372 incident-eligible manufacturing, service and healthcare workers. Workers were followed for an average of 2.5 years (maximum 6 years) and had an average carpal tunnel syndrome (CTS) incidence rate of 4.6 per 100 person-years. Exceeding the a-priori RSI limit of 10.0 showed increased risk of CTS (Hazard Ratio (HR) = 1.45, 95% CI: 1.11–1.91, p = 0.01). There also was a dose-response relationship using proposed low (RSI ≤ 8.5, HR = 1.00), medium (HR = 1.42 (95% CI: 0.96–2.09, p = 0.08)), and high limits (RSI > 15, HR = 1.79 (95% CI: 1.19–2.69, p = 0.01), respectively. RSI as a continuous variable showed CTS risk increased steadily by between 1.9% and 3.3% per unit increase in RSI (p ≤ 0.03). These results suggest that the RSI is a useful tool for surveillance as well as for job intervention/design and continuous improvement processes. Practitioner Summary The Revised Strain Index (RSI) quantifies physical exposure from individual hand/wrist exertions, tasks, and multi-task jobs. Increased cumulative RSI scores (i.e. daily exposure score) are associated with increased risk of carpal tunnel syndrome (CTS). The RSI is potentially useful as a risk surveillance and intervention design tool.

Recent studies have successfully reported the accuracy of using artificial neural networks to predict grip force in controlled settings. However, only relying on accuracy to evaluate the machine learning models may lead to overoptimistic results, especially on imbalanced datasets. The Matthews correlation coefficient (MCC) showed an advantage in capturing all the data characteristics in the confusion matrix. Therefore, a binary classification approach and the MCC value were introduced to assess the performance of previously proposed machine learning models. Our results show that the overall correlations ranging between 0.48 and 0.59 indicate a strong relationship between predictions and actual scenarios. The binary classification approach and the MCC values could be used for future performance comparison with other machine learning models.

The recently revised ACGIH TLV for Hand Activity (TLV2018) is a widely used tool for assessing risk for upper limb musculoskeletal disorders. The purpose of this analysis was to compare the strength of the exposure-response relationships between the TLV2018 and carpal tunnel syndrome (CTS) between men and women and across age strata. Heterogeneity of the effect size by sex or age would be important to specialists using the method for prevention of CTS among working populations. Data from two large prospective studies were combined to allow for stratification of exposure-response models assessing the association between the TLV2018 and CTS by gender and age. Results show greater risk for women than men and for younger workers than older workers for TLV2018 values above the action limit. Although the TLV2018 is an effective surveillance tool for estimating increased risk of CTS with increasing exposure, these analyses show that such increase are not homogeneous across sex and age.

Objective: Assessment of possible relationships between work-related psychosocial measures and self-reported low back pain (LBP) outcomes in a large pooled dataset of 1929 participants from 82 facilities in the United States. Methods: Pooled data from three prospective cohort studies were used to calculate odds ratios (OR) and 95% confidence intervals (95% CI) for relationships between psychosocial factors and the LBP outcomes. Personal and occupational confounders were controlled for in adjusted Logistic regression models. Results: Supervisor support and job satisfaction were significantly (P < 0.05) related to all three LBP outcomes. Other psychosocial factors were significantly (P < 0.05) associated with at least one of the LBP outcomes. Adjusted ORs ranged from approximately 1.50 to 3.50 for most associations. Conclusions: There is a significant relationship between work-related psychosocial measures and LBP outcomes.

Study DesignThis is a cross-sectional, observational study.IntroductionThe disability of the arm, shoulder and hand (DASH) questionnaire is an upper-extremity specific outcome measure commonly used in routine clinical care and clinical trials.Purpose of the StudyOur purposes were to: (1) examine the psychometric properties of the DASH questionnaire using factor analysis, one- and two-parameter item response theory models, and (2) develop a functional staging map illustrating the relationships between the item difficulty hierarchy of the DASH items and the patient's DASH total score.MethodsData from 2724 patients with orthopedic shoulder impairments seeking outpatient physical therapy in 79 clinics in the US were analyzed.ResultsFactor analysis supported a general factor, explaining 62.2% of the total variance. The coverage of DASH items was suitable for patients with shoulder impairments with no ceiling or floor effect. Endorsed items representing the most difficult items were related to feeling less capable, executing recreational activities with force or impact, and performing recreational activities in which you move your arm freely. Items with higher discriminating abilities were those related to do heavy household chores, garden/yard work, and change a light bulb overhead. With a separation index equaled to 4.94, the DASH can differentiate persons into at least 6 statistically distinct person strata. None of the DASH items exhibited differential item functioning by gender or symptom acuity, except two items by age group.DiscussionBesides a total (summed) final score obtained from a specific measure, the keyform and functional staging plots/maps can be used to assist clinicians in clinical interpretation of the scores.ConclusionsResults supported the clinical usage of the DASH questionnaire in patients with orthopedic shoulder impairments seeking outpatient rehabilitation.

INTRODUCTION:Commercial motor vehicle drivers, such as truck drivers, experience unique health, lifestyle, and occupational challenges directly associated with their profession.METHODS:All participants in this multistate cross-sectional study completed questionnaire measurements. Participants were categorized with metabolic syndrome (MetS) if they had at least three of the five modified criteria used in the joint scientific statement on metabolic syndrome.RESULTS:Overall MetS prevalence was 52.4% (n = 428) of the 817 participants. Prevalence of MetS criteria were waist circumference (n = 634, 77.0%), low HDL cholesterol (n = 580, 71.0%), elevated triglycerides (n = 552, 67.6%), elevated blood pressure (n = 175, 21.2%), and elevated hemoglobin A1c (n = 97, 11.9%). Truck drivers were 2.7 times more likely to have MetS compared to the general working population.CONCLUSION:Truck drivers in the United States have a high prevalence of MetS compared to the general working population.

Introduction: Commercial motor vehicle drivers, such as truck drivers, experience unique health, lifestyle, and occupational challenges directly associated with their profession. Methods: All participants in this multistate cross-sectional study completed questionnaire measurements. Participants were categorized with metabolic syndrome (MetS) if they had at least three of the five modified criteria used in the joint scientific statement on metabolic syndrome. Results: Overall MetS prevalence was 52.4% ( n = 428) of the 817 participants. Prevalence of MetS criteria were waist circumference ( n = 634, 77.0%), low HDL cholesterol ( n = 580, 71.0%), elevated triglycerides ( n = 552, 67.6%), elevated blood pressure ( n = 175, 21.2%), and elevated hemoglobin A1c ( n = 97, 11.9%). Truck drivers were 2.7 times more likely to have MetS compared to the general working population. Conclusion: Truck drivers in the United States have a high prevalence of MetS compared to the general working population.

Low back pain (LBP) is a common health problem and a major cause of lost productivity in workplaces. Manual materials handling (MMH) jobs have traditionally been regarded as risk factor for LBP. Compared to two-handed lifting, one-handed lifting has received little attention in both epidemiological and biomechanical research. In addition, one frequent complaint of the revised NIOSH lifting equation (RNLE) has been the lack of capability to directly evaluate one-handed lifting. Modifications have been proposed by the European Union, however their efficacy and influence have not yet been evaluated. This cross-sectional study provided objective survey of the MMH jobs, especially the one-handed lifting performed in manufacturing industry and investigated the outcomes of three proposed methods to address one-handed lifting using RNLE approach. Preliminary results suggest that workers with some one-handed lifting are associated with higher physical exposure. However, the increase was more significant among those who perform primarily one-handed lifting.

Approximately 1.6 million commercial construction workers in the US use rotary hammer drills for drilling into concrete to insert anchor bolts or rebar. The exposure to vibration may lead to hand-arm vibration syndrome and other musculoskeletal disorders depending on handle vibration acceleration level, hand grip force, and duration of exposure. There is little information on the relationship between feed force (FF), e.g., the push force applied by the worker, and handle vibration. A robotic test bench for rotary hammer drills was used to evaluate the effects of different FF on handle vibration and productivity (e.g., penetration rate and holes drilled). Increasing FF from 95 to 163 N was associated with an increase in total weighted handle vibration (a(hv)) of 7.2-8.5 m/s(2) (slope, p < 0.001) but from 163 to 211 N there was no change in vibration level (slope, p=0.17). Increasing FF from 95 to 185 N was associated with an increase in penetration rate of 7.2-8.5 m/s(2) (slope, p < 0.001) but from 185 to 211 N there was no change in penetration rate (slope, p - 0.49). Based on the maximum allowable duration of exposure to hand vibration, specified by the ISO and ACGIH Action Limits, and the penetration rate, the drilling productivity, in m drilled per day, is greatest for the lowest FF tested. Contractors and construction workers should be informed that when drilling into concrete, the lowest exposure to harmful hand vibration and the best overall productivity occurs when the lowest operational FF is applied during hammer drilling.

Study Design: This is a cross-sectional observational study. Background: Reference equations for describing hand-grip strength across the age span were derived from the 2011 NIH Toolbox norming study. Purpose: The purpose of this study was to cross-validate reference equations by evaluating its predicting power on a separate, independent data set from the 2011-2014 National Health and Nutrition Examination Survey (NHANES) study Methods: Observed hand-grip strength data from 13,676 noninstitutionalized participants were obtained from the NHANES study. Best values (best from 3 trials) and the mean values (averaged from 3 trials) were determined for each hand. Using the age (yr), height (m), and weight (kg), we computed predicted grip strength values for dominant and nondominant hands using the reference equations. For validation, three predictability measures: the correlation coefficient, residuals, and accuracy, were used along with the Bland-Altman plot. Results: The predicted values highly correlated with observed values (r = 0.90, ICC = 0.89). In predicting best values, means (SD) of residuals were 1.41 (5.57) and 1.03 (5.44) kg for dominant and nondominant hands, respectively. In predicting mean values, means (SD) of residuals were -0.23 (5.42) and -0.54 (5.31) kg for dominant and nondominant hands, respectively. Root mean square error ranged from 4.10 (female's nondominant mean values) to 6.74 (male's dominant best values). About 5.56% fell outside of the 95% confidence interval of the prediction. Conclusions: We acknowledged that the two studies' hand-grip protocols (NIH Toolbox, NHANES) were different. Results provided the preliminary predicting performance of the reference equations derived from the NIH Toolbox study. (C) 2021 Published by Elsevier Inc. on behalf of Hanley & Belfus, an imprint of Elsevier Inc.

Background:  Previously reported risk factors for common musculoskeletal disorders (MSDs) have been low in magnitude and with unclear pathophysiological mechanisms.  Methods:  Data from a nine-year prospective cohort were analyzed.  Baseline data included computerized questionnaires, structured interviews, physical examinations, anthropometric measurements, nerve conduction studies, and individualized measurement of job physical factors.  Framingham risk scores were calculated.  A priori case definitions were constructed for carpal tunnel syndrome, lateral epicondylopathy, medial epicondylopathy, and rotator cuff tendinopathy.  Monthly follow-ups were conducted to assess symptoms (development, resolution and/or treatments) and to perform physical examinations.  Nerve conduction studies were performed every 6 months if any new-onset paresthesias in the prior six-month interval were reported.    Results:  The relative risk of four different MSDs increased with rising cardiovascular disease risk scores; adjusted relative risks for one or more MSD increased to 3.90 (95% CI, 2.20, 6.90) among those with 10-year cardiovascular risk scores above 15%.  The relative risk of multiple MSDs increased more strongly with rising cardiovascular disease risk; adjusted relative risk for four or more MSDs increased to 17.40 (95% CI, 3.85, 78.62) among those with 10-year cardiovascular risk scores above 15%.  Conclusions: Cardiovascular disease risk factors are strongly associated with the subsequent development of common MSDs.  Risks among those with multiple MSDs are considerably stronger.  Further investigations of this new potential line of prevention are needed, as well as the utility of these MSDs to identify the development of silent coronary artery disease. Funding Statement: This work was supported, in part, by grants from the National Institute for Occupational Safety and Health (NIOSH/CDC) grant 1R01OH010474–01 and NIOSH Education and Research Center training grant T42/CCT810426–10. Declaration of Interests: The authors declare that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. Ethics Approval Statement: Institutional review boards of the University of Utah, University of Wisconsin-Milwaukee and Medical College of Wisconsin approved this study.

Objective: The primary goal of this cross-sectional analysis was to determine the relationships between self-reported low back pain (LBP) ratings and use of opioid medications. Methods: At baseline, subjects completed a computerized questionnaire. Structured interviews were conducted by residents or certified therapists under the direction of board-certified physicians. Results: There was a statistically significant nonlinear relationship between lifetime prevalence of worst LBP rating (0 to 10) and lifetime prevalence of opioid use. Those with a low pain rating for worst lifetime LBP and those with high LBP ratings were significantly more likely to have been prescribed opioids. Surprisingly, those with moderate pain ratings were the least likely to have used opioids. Conclusion: This study found a higher use of opioids between workers with low and high severe pain rating then those with moderate pain. We also found an increase of opioid use for severe pain.