Work-related neck and upper limb disorders - quantitative exposure-response relationships adjusted for personal characteristics and psychosocial conditions.

BACKGROUND: We have previously reported quantitative exposure-response relationships between physical exposures recorded by technical methods, and complaints and diagnoses in the neck/shoulders, and the elbows/hands, based on group data. In the present study the number of workers was doubled, and information on individual factors, and psychosocial working conditions was used. Relationships between various kinds of exposure and response have been analysed in this larger and more detailed sample. METHODS: The prevalence of complaints (Nordic Questionnaire) and diagnoses (clinical examination) were recorded in a number of occupational groups within which the participants had similar work tasks, 34 groups of female employees (N = 4733 women) and 17 groups of male employees (N = 1107 men). Age and other individual characteristics were recorded, as well as psychosocial work environment factors (job-content questionnaire) for most participants. Postures and velocities (inclinometry) of the head (N = 505) and right upper arm (N = 510), right wrist postures and velocities (electrogoniometry; N = 685), and muscular activity (electromyography; EMG) in the right trapezius muscle (N = 647) and forearm extensors (N = 396) were recorded in representative sub-groups. Exposure-response relationships between physical exposure and musculoskeletal disorders, adjusted for individual factors with Poisson regression were then calculated. The effect of introducing psychosocial conditions into the models was also assessed. RESULTS: Associations were found between head velocity, trapezius activity, upper arm velocity, forearm extensor activity and wrist posture and velocity, and most neck/shoulder and elbow/hand complaints and diagnoses. Adjustment for age, other individual characteristics and psychosocial work conditions had only a limited effect on these associations. For example, the attributable fraction for tension neck syndrome among female workers with the highest quintile of trapezius activity was 58%, for carpal tunnel syndrome versus wrist velocity it was 92% in men in the highest exposure quintile. CONCLUSIONS: Based on the findings, we propose threshold limit values for upper arm and wrist velocity.

Exposure-response relationships for work-related neck and shoulder musculoskeletal disorders--Analyses of pooled uniform data sets.

There is a lack of quantitative data regarding exposure-response relationships between occupational risk factors and musculoskeletal disorders in the neck and shoulders. We explored such relationships in pooled data from a series of our cross-sectional studies. We recorded the prevalence of complaints/discomfort (Nordic Questionnaire) and diagnoses (physical examination) in 33 groups (24 female and 9 male) within which the workers had similar work tasks (3141 workers, of which 817 were males). In representative sub-groups, we recorded postures and velocities of the head (N = 299) and right upper arm (inclinometry; N = 306), right wrist postures and velocities (electrogoniometry; N = 499), and muscular activity (electromyography) in the right trapezius muscle (N = 431) and forearm extensors (N = 206). We also assessed the psychosocial work environment (Job Content Questionnaire). Uni- and multivariate linear meta-regression analysis revealed several statistically significant group-wise associations. Neck disorders were associated with head inclination, upper arm elevation, muscle activity of the trapezius and forearm extensors and wrist posture and angular velocity. Right-side shoulder disorders were associated with head and upper arm velocity, activity in the trapezius and forearm extensor muscles and wrist posture and angular velocity. The psychosocial work environment (low job control, job strain and isostrain) was also associated with disorders. Women exhibited a higher prevalence of neck and shoulder complaints and tension neck syndrome than men, when adjusting for postures, velocities, muscular activity or psychosocial exposure. In conclusion, the analyses established quantitative exposure-response relationships between neck and shoulder disorders and objective measures of the physical workload on the arm. Such information can be used for risk assessment in different occupations/work tasks, to establish quantitative exposure limits, and for the evaluation of preventive measures.

Exposure-response relationships in work-related musculoskeletal disorders in elbows and hands - A synthesis of group-level data on exposure and response obtained using uniform methods of data collection.

There is a serious lack of quantitative data regarding exposure-response relationships between occupational risk factors and musculoskeletal elbow and hand disorders. This paper explores such relationships in group-level data from our earlier cross-sectional studies. Prevalence of complaints (Nordic Questionnaire) and diagnoses (physical examination) were recorded in 19 groups of female workers (1891 individuals), and 8 groups of male workers (761 individuals), with highly similar work tasks within each group. Linear regression was performed on the group means of wrist postures and angular velocity (obtained by electrogoniometers), as well as muscular load (obtained using electromyography), recorded in representative sub-samples, and psychosocial exposure (Job Content Questionnaire). To tackle within-group variations in physical exposure, sensitivity analyses were performed by bootstrapping simulations, rendering confidence intervals. The sex-adjusted slope of the regression line (ß) for wrist angular velocity vs. complaints during the past 7 days was 0.6%/(°/s), (95% CI 0.3-0.9), and for carpal tunnel syndrome (CTS) 0.2%/(°/s), (0.1-0.3). For palmar flexion, p50, ß over the past 7 days was 0.8%/° (0.4-1.2); for CTS 0.3%/° (0.1-0.5); ß for muscular activity p90: 0.9%/%MVE (0.3-1.6), and 0.3%/%MVE (-0.03-0.6) respectively and finally ß for muscular rest: -1.2%/%time (-2.4-0.03) and -0.5%/%time (-0.9 to -0.01). Relationships were also demonstrated for low job control, job strain and isostrain. Women exhibited a higher prevalence of complaints than men. In conclusion, we have established quantitative exposure-response relationships between physical work load and elbow/hand disorders. Wrist angular velocity was the most consistent risk factor.

Rationalization in meat cutting - consequences on physical workload.

Meat cutting is associated with several ergonomic risk factors and a high risk of musculoskeletal disorders. The development of new production systems points to an increased degree of mechanization; instead of subdividing split carcasses of pigs with a knife, the halves are trisected by an electrical saw into 'sixth-parts', resulting in shorter work cycles for the workers. Recently, machine-directed line-production systems have been implemented. This study evaluates differences in the physical workload between the production systems. The postures and movements (inclinometry and goniometry) and muscular load (electromyography) of workers in the split-carcass- (five subjects), sixth-part- (ten) and line-production systems (five) were recorded. Most measures showed a statistically significant trend of declining physical exposure with increasing degrees of mechanization. For example, movement velocities of the upper arm were higher in the split-carcass system (50th percentile: mean 209°/s) than in the sixth-part (103°/s) and line production (81°/s). However, the latter two were not statistically significantly different. A novel method for quantifying posture variation, based on inclinometry, showed that the split-carcass system implied the highest variation of the upper arm postures "within-minute" (i.e., a high range of motion each minute), but the lowest "between-minute" (i.e., a low variation during the course of the workday). In conclusion, the physical workload in the line-production system was significantly lower than in the split-carcass one, and tended also to be lower than in the sixth-part system. However, there may be disadvantages in line production, such as machine-directed work pace and shorter work cycles.

Discrepancies in pain presentation caused by adverse psychosocial conditions as compared to pain due to high physical workload?

Disorders in the musculoskeletal system have been associated with a high physical workload as well as psychosocial and individual factors. It is however not obvious which of these factors that is most important to prevent. Musculoskeletal disorders in neck and upper extremity was assessed by interview and clinical examination in 79 teachers and 93 assisting nurses, all females. Psychosocial work environment was assessed by questionnaire. The physical workload was recorded by technical measurements of postures, movements and muscular load, in 9 teachers and 12 nurses. The physical workload was lower among the teachers, but they had a more demanding psychosocial work environment. Among the nurses, but not in the teachers, the neck-shoulder disorders were associated with a high body mass index (BMI). The teachers reported neck-shoulder complaints to a higher extent than the nurses, but had much lower prevalence of diagnoses in the clinical examination (12% vs. 25%; POR 0.3 CI 0.1 - 1.2; adjusted for age and BMI). The results suggest that adverse psychosocial conditions among the teachers give rise to a different kind of pain in the neck-shoulder region than from physical overload, troublesome but not as severe as the one afflicting the nurses.

Can the job content questionnaire be used to assess structural and organizational properties of the work environment?

OBJECTIVE: The theory behind the Job Content Questionnaire (JCQ) presumes that the "objective" social environment is measurable via self-report inventories such as the JCQ. Hence, it is expected that workers in identical work will respond highly similar. However, since no studies have evaluated this basic assumption, we decided to investigate whether workers performing highly similar work also responded similarly to the JCQ. METHODS: JCQ data from a rubber-manufacturing (RM: n = 95) and a mechanical assembly company (MA: n = 119) were examined. On each worksite, men and women performed identical machine-paced job tasks. A population sample (n = 8,542) served as a reference group. RESULTS: In both the RM and MA groups, the job support questions were rated most similar. Yet, there was a substantial variation as regards choosing to agree or disagree with single JCQ items. The variation was also reflected in the scale scores. In the RM and MA groups, the variance of job demand and job control scores was 64-87% of that of the population sample. For job support scores, the corresponding variation was 42-87%. CONCLUSION: Conducting highly similar work does not lead to highly similar reports in the JCQ. In view of the large response variation, it seems that the attempt to avoid personal influence by minimizing the self-reflexive component in the questions asked, and using response alternative that indicates degree of agreement, does not seem to work as intended.

Risk of musculoskeletal disorders among females and males in repetitive/constrained work.

This paper combines epidemiological data on musculoskeletal morbidity in 40 female and 15 male occupational groups (questionnaire data 3720 females, 1241 males, physical examination data 1762 females, 915 males) in order to calculate risk for neck and upper limb disorders in repetitive/constrained vs. varied/mobile work and further to compare prevalence among office, industrial and non-office/non-industrial settings, as well as among jobs within these. Further, the paper aims to compare the risk of musculoskeletal disorders from repetitive/constrained work between females and males. Prevalence ratios (PR) for repetitive/constrained vs. varied/mobile work were in neck/shoulders: 12-month complaints females 1.2, males 1.1, diagnoses at the physical examination 2.3 and 2.3. In elbows/hands PRs for complaints were 1.7 and 1.6, for diagnoses 3.0 and 3.4. Tension neck syndrome, cervicalgia, shoulder tendonitis, acromioclavicular syndrome, medial epicondylitis and carpal tunnel syndrome showed PRs > 2. In neck/shoulders PRs were similar across office, industrial and non-office/non-industrial settings, in elbows/hands, especially among males, somewhat higher in industrial work. There was a heterogeneity within the different settings (estimated by bootstrapping), indicating higher PRs for some groups. As in most studies, musculoskeletal disorders were more prevalent among females than among males. Interestingly, though, the PRs for repetitive/constrained work vs. varied/mobile were for most measures approximately the same for both genders. In conclusion, repetitive/constrained work showed elevated risks when compared to varied/mobile work in all settings. Females and males showed similar risk elevations. This article enables comparison of risk of musculoskeletal disorders among many different occupations in industrial, office and other settings, when using standardised case definitions. It confirms that repetitive/constrained work is harmful not only in industrial but also in office and non-office/non-industrial settings. The reported data can be used for comparison with future studies.

Physiological and psychological reactions to work in men and women with identical job tasks.

Differences in physiological functioning in the hypothalamus-pituitary-adrenal cortex axis and the autonomic nervous system have been suggested to contribute to many of the health differences that may be observed between men and women as well as being relevant for the development of musculoskeletal pain. To clarify whether men and women with identical work tasks reacted differently when doing work known to induce musculoskeletal pain, ratings and physiological measurements were obtained at work start (15:30) and at the end of the workshift (22:30) on 17 men and 20 women. Men showed a larger decrease in perceived energy levels during the workshift but there were no differences between men and women as regards cortisol, adrenaline, noradrenaline, heart-rate activation, perceived stress, pain and physical exertion. In conclusion, differential physiological activation during the workshift seem to be an unlikely mechanism for explaining gender differences in pain associated with exposure to awkward and repetitive movements.

Gender differences in workers with identical repetitive industrial tasks: exposure and musculoskeletal disorders.

OBJECTIVES: For unknown reasons, females run a higher risk than males of work-related musculoskeletal disorders. The aim of this study was to evaluate whether male and female workers, with identical repetitive work tasks, differ concerning risk of disorders, physical or psychosocial exposures. METHODS: Employees in two industries were studied; one rubber manufacturing and one mechanical assembly plant. These industries were selected since in both, large groups of males and females worked side by side performing identical repetitive work tasks. Physical exposure was measured by technical equipment. Postures and movements were registered by inclinometry for the head and upper arms, and by electrogoniometry for the wrists. Muscular activity (muscular rest and %max) was registered by surface electromyography for m. trapezius and the forearm extensors (18 males and 19 females). Psychosocial work environment was evaluated by the demand-control-support model (85 males and 138 females). Musculoskeletal disorders were assessed (105 males and 172 females), by interview (last 7-days complaints), and by physical examination (diagnoses). RESULTS: Concerning physical exposure, females showed higher muscular activity related to maximal voluntary contractions [(%MVE); m. trapezius: females 18 (SD 9.2), males 12 (SD 4.3); forearm extensors: females 39 (SD 11), males 27 (SD 10), right side, 90th percentile]. Working postures and movements were similar between genders. Also, concerning psychosocial work environment, no significant gender differences were found. Females had higher prevalences of disorders [complaints: age-adjusted prevalence odds ratio (POR) 2.3 (95% CI 1.3-3.8) for neck/shoulders, 2.4 (1.4-4.0) for elbows/hands; diagnoses: neck/shoulder 1.9 (1.1-3.6), elbows/hands 4.1 (1.2-9.3)]. In 225 workers, PORs were adjusted for household work, personal recovery and exercise, which only slightly affected the risk estimates. CONCLUSION: In identical work tasks, females showed substantially higher muscular activity in relation to capacity, and higher prevalence of musculoskeletal disorders of the neck and upper extremity, than did males.

Differences in physical workload, psychosocial factors and musculoskeletal disorders between two groups of female hospital cleaners with two diverse organizational models.

OBJECTIVES: To clarify if differences in the physical workload, the psychosocial factors and in musculoskeletal disorders can be attributed to work organizational factors. METHODS: The physical workload (muscular activity of m. trapezius, positions and movements of the head, upper arms and wrists and heart rate) was assessed in 24 female hospital cleaners working in a traditional work organization (TO) and in 22 working in an extended one (i.e. with an enlarged work content and more responsibilities; EO). The psychosocial work environment was assessed as job demand, decision latitude and social support in 135 (TO) and 111 (EO) cleaners, and disorders of the neck and upper extremity by a physical examination. RESULTS: The EO group was associated with lower physical workload, in terms of heart rate ratio (23 vs 32; P<0.001), head and upper arm positions and movements (right upper arm, 50th percentile, 35 degrees/s vs 71 degrees/s; P<0.001) and wrist movements (20 degrees/s vs 27 degrees/s; P=0.001), than the TO group. The EO group reported higher decision latitude and lower work demand than the TO one, while we found no difference in social support. The prevalence of complaints and diagnoses in neck/shoulders were lower in the EO group (diagnoses 35% vs 48%; P=0.04). Moreover, the prevalence of subjects with at least ten physical finding in elbows/hands was lower in the EO group (10 vs 29; P<0.001). CONCLUSION: Hospital cleaners have a high prevalence of neck and upper limb disorders and a high physical workload. Comparing two groups of cleaners, with differences in the way of organizing the work, lower physical workload, more beneficial psychosocial factors and a better musculoskeletal health was found in the group with an extended organization. Hence, the differences found can be attributed to the organizational factors.

Physical workload on neck and upper limb using two CAD applications.

The aim was to evaluate (1) the physical workload on neck and upper limb in computer-aided design (CAD) work; (2) the impact of two applications (PROFESSIONAL-CADAM and PRO/Engineering) and (3) two input devices (computer mouse and keyboard), as well as (4) sitting and standing work positions. Fifteen CAD operators were interviewed and examined physically. For nine subjects, the physical workload was measured: electromyography (EMG) of trapezius and forearm extensor muscles, inclinometry of the head, the upper back and upper arms, as well as wrist goniometry. The muscular load was low in CAD work, but the inter-individual variation was considerable. Neither the positions were extreme, nor the movements. The applications, per se, did not have a large impact on the workload, but because of the need for different input devices the effect was strong. Using a keyboard meant higher angular velocities than using a mouse. Hence, when choosing a new software, which requires mainly a mouse as input device, this has to be balanced against the risk of disorders.