In spite of extensive research efforts in epidemiology and applied physiology, the critical exposure determinants of upper extremity and neck disorders in occupations with medium or low exposure levels are still unresolved, let alone the mechanisms explaining why those determinants would have an effect on, e.g. pain and performance.
An increasing interest has been paid to the basic hypothesis that risk may increase when an imbalance between exposure and recovery occurs, rather than as a result of the average exposure level per se. Thus, according to this hypothesis, the temporal pattern of exposure, i.e. exposure variation, is crucial to risk. This paradigm drives programme A, the superior goal of which is to understand the effects of physical and mental variation on musculoskeletal health, well-being and performance, for the purpose of designing sustainable jobs.
The focus on variation implies that controlled laboratory studies of possible mechanisms leading to disorders need investigate responses to different exposure time-lines (beyond the classical issue of intermittent isometric exercise with rest breaks); epidemiologic cohort studies need address associations between time-domain exposure variables and outcomes of interest (performance, well-being, disorders); intervention studies need examine the feasibility and effect of possible sources of variation in occupational settings, including intrinsic sources (e.g. working technique, motor variability) and extrinsic initiatives (e.g. combining tasks to give exposure time lines with ample variation, or introducing activities promoting recovery); and this research needs be accompanied by developing standardized methods with known properties (validity, statistical performance) for quantifying the extent of variation in naturally occurring exposure time lines.
Svend Erik Mathiassen