The high economical costs produced by the impact of low back pain on sick-listing and loss of manpower at work encouraged the search for personal or situational characteristics that indicate an increased risk for an acute onset of back pain or for its continuation towards chronicity. Risk factors for the onset of acute pain identified at the workplace refer to mechanical and psychomental strain. Vibration as well as lifting and carrying of heavy loads, especially if combined with a twisting of the trunk, are the most prominent mechanical risks, whereas dissatisfaction with the job or the working conditions, especially if there is a lack of social support either at the workplace or at home by the family or the spouse, increase the risk on a psychosocial level. Although these risks continue to be effective in the process of chronicity, other risks pertaining to behavioral and emotional reactions to the acute pain episode gain in importance. At the acute level, avoidance of physical and social activities are often encouraged by physicians who prescribe bed rest or give advice to regulate the active reinvolvement in daily life by assessing pain levels ('let the pain guide'). On the other hand, with regard to the prevention of chronicity, a strategy of graded early activation aiming at a reinforcement of healthy behaviors has more beneficial effects. After a short period of bed rest, no longer than two days, if at all necessary, patients are taught to maintain their daily activities and to practice specified exercises, while receiving time-contingent pain medication.(ABSTRACT TRUNCATED AT 250 WORDS)