The impact of physical load on the course of low back pain

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