| 1. |
- Hansson, Gert-Åke, et al.
(författare)
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Precision of measurements of physical workload during standardised manual handling. Part II: Inclinometry of head, upper back, neck and upper arms
- 2006
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Ingår i: Journal of Electromyography & Kinesiology. - : Elsevier BV. - 1050-6411 .- 1873-5711. ; 16:2, s. 125-136
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Tidskriftsartikel (refereegranskat)abstract
- For measuring the physical exposure/workload in studies of work-related musculoskeletal disorders, direct measurements are valuable. However, the between-days and between-subjects variability, as well as the precision of the method per se, are not well known. In a laboratory, six women performed three standardised assembly tasks, all of them repeated on three different days. Triaxial inclinometers were applied to the head, upper back and upper arms. Between-days (within subjects) and between-subjects (within tasks) variance components were derived for the 10th, 50th and 90th percentiles of the angular and the angular velocity distributions, and for the proportion of time spent in predefined angular sectors. For percentiles of the angular distributions, the average between-days variability was 3.4 degrees , and the between-subjects variability 4.0 degrees . For proportion of time spent in angular sectors, the variability depended on the percentage of time spent in the sector; the relative variability was scattered and large, on average 103% between days and 56% between subjects. For the angular velocity percentiles, the average between-days variability was 7.9%, and the average between-subjects variability was 22%. The contribution of the measurement procedure per se to the between-days variability, i.e., the imprecision of the method, was small: less than 2 degrees for angles and 3% for angular velocity.
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| 2. |
- Mathiassen, Svend Erik, et al.
(författare)
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Task-based estimation of mechanical job exposure in occupational groups
- 2005
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Ingår i: Scandinavian Journal of Work, Environment and Health. - 0355-3140 .- 1795-990X. ; 31:2, s. 138-51
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: This study examined the validity of a common belief in epidemiology with respect to work-related musculoskeletal disorders, that individual mechanical job exposure is better estimated from tasks performed in the job than from the mean exposure of the occupational group. METHODS: Whole-day recordings of upper trapezius electromyography were obtained from 24 cleaners and 23 office workers. Trapezius activity was analyzed in the level (gap time) and frequency (jerk time) dimensions. On the same day, the job of each person was divided into periods of active work and breaks by means of continuous observations. The bootstrap re-sampling technique was used with this database to compare task-based job exposure estimates with estimates based on the occupational mean. For a particular person, the task-based estimate was obtained by combining the average work and break exposures in the occupation with the personal time proportions of the two tasks in the job. RESULTS: The task-based estimates were, in general, equivalent to, or less correct than, occupation-based estimates for both exposure parameters in both occupations and for individual exposures, as well as for group means. This was the result in spite of significant and consistent exposure differences between work and breaks, in particular among the cleaners. CONCLUSIONS: Even if task exposure contrasts are large, task-based estimates of job exposures can be less correct than estimates based on the occupational mean. Since collecting and processing task information is costly, it is recommended that task-based modeling of mechanical exposure be implemented in studies only after careful examination of its possible benefits.
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