Study Design. A systematic review of randomized controlled trials was performed. Summary of Background Data. Exercise therapy is a widely used treatment for low back pain. Objectives. To evaluate the effectiveness of exercise therapy for low back pain with regard to pain intensity, functional status, overall improvement, and return to work. Methods. The Cochrane Controlled Trials Register, Medline, Embase, PsycLIT, and reference lists of articles were searched. Randomized trials testing all

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... s of exercise therapy for subjects with nonspecific low back pain with or without radiation into the legs were included. Two reviewers independently extracted data and assessed trial quality. Because trials were considered heterogeneous with regard to study populations, interventions, and outcomes, it was decided not to perform a metaanalysis, but to summarize the results using a rating system of four levels of evidence: strong, moderate, limited, or none. Results. In this review, 39 trials were identified. There is strong evidence that exercise therapy is not more effective for acute low back pain than inactive or other active treatments with which it has been compared. There is conflicting evidence on the effectiveness of exercise therapy compared with inactive treatments for chronic low back pain. Exercise therapy was more effective than usual care by the general practitioner and just as effective as conventional physiotherapy for chronic low back pain. Conclusions. The evidence summarized in this systematic review does not indicate that specific exercises are effective for the treatment of acute low back pain. Exercises may be helpful for patients with chronic low back pain to increase return to normal daily activities and work. [