Previous reviews have claimed that it is difficult to conclude whether exercise therapy is effective in the treatment of chronic low back pain (LBP). It has been concluded that the trials covering this area have low methodological quality. Little attention has been paid to the actual intervention applied in such trials. A potential effect has to be based on existing theoretical principles of exercise physiology. The objective with this systematic review is to evaluate the efficacy of exercise in the treatment of chronic LBP, with emphasis on dose and type of exercise as well as methodological quality. Medline and SPORT searches (1966 to 1995), and manual searches from relevant reference lists were undertaken. Internal validity was assessed by using a list of predefined criteria. Nine randomized trials were included. Six trials evaluated the effect of exercise versus control treatment (RCTs), and three compared different exercise interventions. Inadequate reports of descriptive statistics and heterogeneity across across included studies made a statistical meta-analysis impossible. Internal validity scores varied from seven to 26 points on a scale from zero to 39 points. The number of RCTs were too small to analyse whether variation in internal validity could explain divergent results across studies. Length of exercise interventions varied from 2 weeks to 3 months, the total number of sessions from eight to 270, the repetition number per session from 60 to 300, and consisted either of flexion and/or extension exercises. No firm conclusions concerning efficacy of exercise in the treatment of chronic LBP can be drawn from the existing RCTs retrieved in the present review. There is a need for more trials with high internal validity, and exercise protocols grounded on established theoretical principles concerning type and dose of exercises.

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A brief summary and a critical assessment of this review may be available at DARE