PROJECT SUMMARY: Back pain is one of the most prevalent conditions afflicting American adults and is the leading reason for using complementary and alternative medical (CAM) therapies. Yoga is an increasingly popular "mind-body" CAM therapy often used for relieving back pain and several small studies have found yoga effective for this condition. The proposed randomized trial will determine if yoga is an effective treatment for chronic low back pain compared with usual care and exercise and if so, will explore the mechanisms responsible for its benefits. A total of 210 participants with low back pain lasting at least 3 months will be recruited from primary care clinics of a large healthcare system based in Seattle. They will be randomized in a 2:2:1 ratio to receive 12 weekly yoga classes, 12 weekly conventional therapeutic exercise classes of comparable physical exertion, or usual care. Interviewers masked to participants'treatment group will assess outcomes at baseline and 6, 12 and 26 weeks after randomization. Primary outcomes will be back-related dysfunction and symptom bothersomeness. In addition, data will be collected on physical measurements (e.g., flexion) at baseline and 12 weeks and salivary samples will be obtained at baseline, 6 and 12 weeks. Information will be collected on specific physical, psychological, and physiological factors to allow exploration of possible mechanisms of action through which yoga could relieve back pain and dysfunction. The effectiveness of yoga will be assessed using analysis of covariance (GEE) within an intention-to-treat context. If yoga is found effective, further analyses will explore whether yoga's benefits are attributable to physical, psychological and/or physiological factors. This study will provide the clearest evidence to date about the value of yoga as a therapeutic option for treating chronic back pain, and if the results are positive, will help focus future, more in-depth, research on the most promising potential mechanisms of action identified by this study. RELEVANCE: Chronic low back pain is a major public health problem affecting millions of Americans and resulting in huge medical care and disability costs and lost productivity. This study will determine if yoga is more effective for chronic back pain than usual medical care or conventional exercise, and if so, if any of yoga's advantages may be attributed to its effects on the mind as well as on the body.