2. A clinical diagnosis of nonmalignant, chronic low back pain (CLBP). LBP, as defined by Quebec Task Force in class 1 - pain without radiation and class 2 - pain with proximal radiation above the knee. CLBP is defined as being present for at least several hours a day, at least half the days in the previous 6 months, and being the principal pain condition. (In accordance with the NIH 2013 Task Force on Research Standards for Chronic Low Back Pain).