The researchers assigned patients at random to receive 1) 12 weekly 75-minute yoga classes designed for patients with back pain and instructions to practice daily at home; 2) 12 weekly 75-minute sessions of aerobic, strengthening, and stretching exercises, which were developed by a physical therapist, and instructions to practice daily at home; or 3) a personal copy of The Back Pain Helpbook by Jim Moore and colleagues (Reading, MA: Perseus Books; 1999). Study patients could use drugs, such as anti-inflammatory agents or acetaminophen, as needed. Interviewers, who did not know which treatment each patient received, called patients after 6, 12, and 26 weeks and used standard questions to collect information on pain and dysfunction.