The design of assessment strategies depends on the risk factors of interest, features of the measurement device, feasibility considerations, and variation at the workplace. The selection of variables should permit specific etiologic inferences. Several researchers have combined different methods into a broad array of exposure measures. Other authors have converted inputs from disparate methods into a common exposure metric, varying from subjective ratings to quantitative measures such as compression forces in the lumbar back. The parameterization of an exposure variable should address the 3 principal exposure dimensions intensity, frequency, and duration. Standardized expressions of variation patterns of exposure have been suggested. An alternative approach is the modeling of exposure variability that allows for exposure assessment at the individual level. A related topic is the critical time window of risk factors for musculoskeletal disorders. This window not only requires detailed information of exposure events over time, but also appropriate characterization of episodic musculoskeletal problems.

Key terms epidemiology; exposure modeling; review