This thesis is divided in three parts. Part 1 focuses on the methodology used to
characterize physical work load as risk factor for LBP. In Part 2 dose-response relations
of occupational exposure to physical and psychosocial factors and LBP are evaluated. In
Part 3 the information on dose-response relations is used to simulate the dynamic course
of LBP over time by continuing exposure to physical load.
In Chapter 2 of Part 1 we review the scientific literature on work-related back
disorders in order to evaluate the strength of the associations between physical load and
LBP among different studies, and, secondly, to analyze whether the strength of the
associations can partly be explained by the study design and methods used to
characterize physical work load. In Chapter 3 we propose a novel approach to evaluate
simultaneously level, frequency, and duration of lumbar posture during work in order
to determine the essential characteristics in postural load. In Chapter 4, the last Chapter
of Part 1, two important features in modeling dose-response relations between physical work load and LBP are evaluated: the measurement strate
