Proceedings of the IEA 2000/HFES 2000 Congress, Vol. 5, San Diego, CA, July 30-August 4, 2000. Santa Monica, CA: Human Factors and Ergonomics Society, 2000 Jul; 5:720-723
Widely accepted guidelines, such as the revised NIOSH Lifting Equation (Waters, 1994) are available to evaluate physical stressors of the back, but similar guidelines for the upper extremities are unavailable. Although many exposure assessment methods have been used in studies to evaluate physical stressors to the upper extremities, they tend to be specific to one type of work or limited in the range of stressors that they assess. If researchers can agree on how to measure repetitiveness, force, awkward postures, and other physical stressors in a way that applies to all or most jobs, data could be pooled to advance our knowledge of relationships between these stressors and upper extremity MSDs. Better quantitative or at least semi-quantitative measures would improve our ability to assess dose-response relationships between specific stressors and health outcomes. This paper describes an effort by a group of NIOSH researchers to develop a standard method to evaluate physical stressors of the 'upper extremities in epidemiologic field studies. Workplace physical stressors associated with musculoskeletal disorders (MSDs) include highly repetitive or static muscle exertion, work requiring high force, insufficient recovery time, awkward postures, localized contact pressure, vibration, and cold (Bernard, 1997). Direct reading instruments can provide objective, quantitative information about these stressors in laboratory studies, but are infrequently used in large field studies. Expense and interference with work limit the use of instrumentation in field studies that evaluate different stressors (e.g., force, posture and repetition) at multiple body locations simultaneously. Workers' self-reported ratings of ergonomic stressors via questionnaires have been widely used in field studies, with varying reports on reliability and validity. Observational methods are most commonly used in field studies, with analysts counting, rating, or noting the presence of ergonomic stressors, either from direct observation of workers in the field or from videotapes. Observational methods are widely used in epidemiologic studies (Kilbom, 1994). Recent research has resulted in improvements in these methods, including improving reliability (Keyserling, 1986; Vander Beek, 1992; Burt and Punnett, 1999), and standardizing classifications for postures (Juul-Kristensen, 1997). Quantitative information such as weights of objects and production figures often are used to supplement observations. An ideal method would be reliable and valid, inexpensive and practical for use in large studies, and would apply to a wide variety of jobs. Kilbom. (1994) stressed that although several methods summarize exposure data into an index intended for priority setting for ergonomic interventions, they have not been fully validated, and should never be used in a way that obscures an analysis of the effects of single exposure variables.
Proceedings of the IEA 2000/HFES 2000 Congress, Vol. 5, San Diego, CA, July 30-August 4, 2000