[Stress-strain approach--a principle for ergonomic studies]

In the terminology of occupational hygiene and the WAO no distinction has been made to date between "load" and "strain". Occupational medicine and ergonomics by contrast, in addition to differentiating between the terms, have been developing the "load-strain approach" since about 1970. After outlining the historical development of the terms and explaining them, the approach is derived and presented in a simple and extended form. Starting from demands made by the WAO, the significance of the approach for the planning and execution of ergonomic investigations is explained. In the approach differentiation between the "description", "assessment" and "judgement" of working conditions is recommended. Possible approaches and criteria for forming a judgment are presented and discussed, with special attention being paid to models for the operationalization of strain. A concept for pragmatic judgment is presented after discussion about the necessity, frequently encountered in practice, of balancing the demands of providing scientific proof and of arriving at decisions relevant to practical problems.