Barbara Silverstein

Comparison of self-report, video observation and direct measurement methods for upper extremity musculoskeletal disorder physical risk factors

The prevention of work-related musculoskeletal disorders has become a national priority in many countries. Increasingly, attempts are made to quantify those exposures that increase risk in order to set exposure limit values. This study used commonly employed field measurement methods and tools in order to perform an inter-method comparison between three primary methods of risk factor exposure assessment: self-report questionnaires, observational video analysis and direct measurement. Extreme posture duration, repetition, hand force (estimated from electromyography) and movement velocity were assessed for 18 subjects while performing each of three jobs processing tree seedlings. Results indicated that self-reports were the least precise assessment method, which consistently overestimated exposures for each of the measured risk factors. However, adjustment of the reports as psychophysical scales may increase agreement on a group level. Wrist flexion/extension duration and repetition were best measured by electrogoniometer. Electrogoniometric measures of wrist deviation duration and frequency were less precise than video analysis. Forearm rotation duration and repetition, grip force and velocity appeared to be best quantified by direct measurement as measured by electrogoniometer and electromyography (EMG) (as root-mean-square amplitude). The results highlight the fact that it is as important to consider and report estimated measurement error in order to reduce potential exposure misclassification in epidemiologic studies.

Underreporting of work-related injury or illness to workers' compensation : Individual and industry factors

Objective: We quantified the underreporting of work-related injury or illness to workers’ compensation (WC). Methods: Using data from 2612 wage-earning respondents who participated in the 2002 Washington State Behavioral Risk Factor Surveillance System, we assessed work-related injury or illness in the previous year and identified the factors associated with WC claim filing by logistic regression. Results: The self-reported rate of work-related injury or illness of respondents was 13%. Among those who had a work-related injury or illness, 52% filed a WC claim. After adjustment for age, gender, and race, those who filed WC claims were more likely to be overweight and married. WC claim filing varies considerably across industry and occupation groups holding all other measured factors constant. Conclusions: Individual and industry/occupation factors are related to underreporting of work-related injury or illness to the WC system.

Rotator cuff syndrome: personal, work-related psychosocial and physical load factors.

Objective: To identify factors associated with rotator cuff syndrome (RCS) among active workers. Methods: Seven hundred thirty-three workers in 12 worksites participated in a cross-sectional study with individual structured physical and psychosocial health interviews, physical examinations, and exposure assessments of biomechanical factors. Work organization, including job content or structural constraints, was assessed at the departmental level. Multivariable logistic modeling was used. Results: Fifty-five subjects (7.5%) had RCS. Cases were more likely to report low job security (P < 0.04) and to have very high job structural constraints (P < 0.03). Age and body mass index were marginally significant. Upper arm flexion ≥ 45° ≥ 15% of time and either duty cycle of forceful exertions ≥9% time (odds ratio = 2.43, 95% CI = 1.04 to 5.68) or forceful pinch >0% [odds ratio = 2.66, 95% CI = 1.26 to 5.59] were significant risk factors. Conclusions: Long duration of shoulder flexion and forceful exertion (especially pinch) in a job are significant risk factors for RCS. Work organization may impact physical and psychosocial exposures and should be further explored.

Workplace Changes Associated with a Reduction in Musculoskeletal Symptoms in Office Workers

The purpose of this study was to identify factors associated with reductions observed in musculoskeletal symptoms when office workers were moved to a new building. A questionnaire including items regarding symptoms and aspects of the work environment was administered to 577 office workers before and after they were moved from nine buildings to a single new facility in 1992. Employees working in two reference buildings, where they remained throughout the study period, were also surveyed. Two musculoskeletal outcomes, hand/arm and neck/shoulder/back, were selected for study. In matched multivariate analyses, the reduction in hand/arm symptoms from 1992 to 1993 was associated with improved satisfaction with the physical workstation (odds ratio [OR] = 2.0); the reduction in neck/shoulder/back symptoms was associated with improved chair comfort (OR = 1.8), fewer housekeeping responsibilities (OR = 3.6), female gender (OR = 1.8), and low pay range (OR = 1.7). Longitudinal results suggested that changes in workstations resulted in decreased symptoms. Results of this investigation might be used to develop workplace changes that result in reductions of musculoskeletal disorders

Observational Analysis of the Hand and Wrist: A Pilot Study

Abstract A system for quantitative analysis of risk factors associated with cumulative trauma disorders of the hand and wrist was developed and tested in a pilot study. To use the system, analysts observed the worker and counted the total number of hand exertions per work cycle and the number of exertions associated with specific risk factors such as high force or adverse postures. Pilot study analyses were performed both at the job site and from videotapes of the jobs. Analyses of hand posture performed at the job site provided more accurate data than did analyses performed from videotapes. Compared to analysis methods that utilize frame-by-frame review of videotape or film, the proposed system required considerably less time. Agreement among analysts was strong. The system may be used for quantitative descriptions of ergonomic risk factors on hand-intensive jobs, pre- and postintervention comparisons of engineering and administrative controls, and exposure classification in epidemiologic studies of work...

Estimation of hand force in ergonomic job evaluations.

The aims of the present study were: (1) to collect normative data of pinch and power grip strength with a newer digital dynamometer; (2) to study the ability of hand grip force matching using a hand dynamometer where the validity and reliability issues were studied; and (3) to study the relationship between hand grip force matching and muscle activities of three forearm and hand muscles. This study consisted of two experiments. One hundred and twenty subjects volunteered in the first experiment, where hand grip strength and hand force estimation data were collected. The second experiment had 14 volunteers, where muscle activities of the hand and forearm were collected during the tests of hand grip strength and hand force matching estimations. Results showed that the power grip and pinch grip strengths collected with a newer digital dynamometer were comparable to similar studies using older equipment. At the group level, the force matching method was largely accurate and consistent. Instructions to the subjects about force matching estimation were important to the accuracy and consistency of the estimated forces. Estimation in force matching might depend on perceptions of several major muscle activities.

Quantifying repetitive hand activity for epidemiological research on musculoskeletal disorders--part II: comparison of different methods of measuring force level and repetitiveness.

This paper focuses on comparisons between the different methods of assessing repetitive hand activities. Various methods were used to measure hand force and repetitiveness of hand activities on 733 subjects in the study described by Bao et al. (2006). Two definitions of repetitiveness were used in analysis of detailed time studies of repetitive hand activities and four parameters of the American Conference of Governmental Industrial Hygienists (ACGIH) hand activity level (HAL) and the Strain Index methods were estimated by ergonomists and used to quantify repetitiveness. Hand forces were measured or estimated using three different methods: 1) measured with a force gauge or mimicked on a force gauge (force matching); 2) estimated by ergonomists using rating scales; 3) self-reports by subjects. The jobs were also evaluated using the ACGIH HAL and Strain Index methods when different repetitiveness quantification methods were used. Results showed that different definitions of repetitive exertion might lead to measuring different physical exposure phenomena and produce very different results. There were poor correlations between the measures of repetitiveness estimated by the different methods. Correlations between force quantifications using different methods were also poor. This suggests that parameters measured by different methods might not be interchangeable. Both the ACGIH HAL and Strain Index methods identified more ‘hazardous’ jobs when repetitiveness was estimated by ergonomists than when it was calculated by detailed time studies of forceful hand exertions. The Strain Index method identified more ‘hazardous’ jobs than the ACGIH HAL method. Overall, the between-methods agreements were found to be moderate to substantial.

Risk factors for work-related musculoskeletal disorders in an aluminum smelter

A cross-sectional study of selected jobs in an aluminum smelter was conducted to assess the prevalence of work-related musculoskeletal disorders (WMDs), and to estimate their association with physical and psychosocial characteristics of the jobs. A structured interview and physical exam were used to assess the musculoskeletal health status of the participants, and a self-administered questionnaire was used to assess the psychosocial factors. Observational job analysis was conducted to evaluate 37 potential physical risk factors. Complete data were available for 104 subjects. The prevalence of WMDs on interview and physical exam were 0.8%, 14.9%, 11.6%, 14.9%, and 17.4% for the neck, shoulder, elbow/forearm, hand/wrist, and low back regions, respectively. Unconditional multiple logistic regression was used to model the relationship between physical and psychosocial factors and health status. Years of forearm twisting were found to be a significant predictor for hand/wrist disorders on interview (OR = 17, 95% CI = 2.9-106); for elbow/forearm disorders on physical exam and interview (OR = 37, 95% CI = 3.0-470); and for shoulder disorders on interview (OR = 92, 95% CI = 7.3-infinity) and on interview and physical exam (OR = 46, 95% CI = 3.8-550). Low decision latitude was also found to be significant for the shoulder on interview (OR = 4.5, 95% CI = 1.3-16). High job satisfaction (OR = 5.9, 95% CI = 1.4-25) and low social support (OR = 5.3, 95% CI = 1.3-22) were associated with low back pain report on interview; only high job satisfaction (OR = 5.3, 95% CI = 1.1-26) was associated with low back pain on both interview and physical exam.

Two posture analysis approaches and their application in a modified Rapid Upper Limb Assessment evaluation

This paper presents two posture risk quantification methods: first, an event-based method where the most common and the worst postures are estimated in a task; second, a time-based method where posture distributions are calculated from random samples of observed postures in the task. A ‘click-on-screen’ posture data entry method was developed for the time-based posture analysis method to make the observation process easier and to reduce possible posture categorization bias. Both methods were used to quantify various work posture parameters among a study cohort of 733 subjects from a prospective epidemiological study of upper extremity musculoskeletal disorders. Composite posture indices using a modified Rapid Upper Limb Assessment (RULA) method were also computed using data obtained by the two posture analysis methods. Results showed that both methods were able to distinguish jobs with large differences in certain posture measures. However, they did not produce the same results and could not be used interchangeably. Risk evaluation criteria should be developed, either for specific posture parameters or as a composite index, with a well-defined postural analysis method, so that users can follow exact procedures and obtain comparable results. The event-based method is easy to use and may suit practitioners better, while the time-based method adds more information to the measurement and may suit users who want more detailed information about posture exposure.

Quantitative exposure-response relations between physical workload and prevalence of lateral epicondylitis in a working population.

BACKGROUND Lateral epicondylitis is a common work-related musculoskeletal disorder. The objective of this study was to identify risk factors associated with lateral epicondylitis among active workers. METHODS Seven-hundred thirty-three workers in 12 Washington worksites participated in structured interviews, physical examinations, and individual exposure assessments of biomechanical and psychosocial factors. Multivariable logistic modeling was used. RESULTS Thirty-eight subjects (5.2%) had lateral epicondylitis. Age (36-50 years-old), being female, and low social support at work were significant risk factors. Frequency of forceful exertion (> or =5 vs. < 1 times/min (OR 5.17, 95%CI 1.78-15.02), and > or =1 to <5 vs. <1 (OR 4.47, 95%CI 1.57-13.71)) and forearm supination at > or =45 degrees for > or =5% of the time with high lifting force (OR = 2.98, 95% CI 1.18-7.55) were significant physical load factors. CONCLUSIONS Frequency of forceful exertion or a combination of forearm supination and forceful lifting were significant physical factors and should be considered for prevention strategies.