This randomized controlled study will evaluate the cost effectiveness of a yoga intervention compared to two evidence based programs; giving advice to stay active and guided exercise sessions. The first active program includes a six week standardized strength training program where the participants are personally instructed by a trained physiotherapist. The second active program is a six week standardized kundalini yoga program with group sessions twice a week lead by an experienced yoga instructor. Both programs consist of two exercise sessions per week and lasts for six weeks. After six weeks the participants are instructed to continue practicing their program twice a week on their own. The hypothesis are that a kundalini yoga program as an early intervention for Low Back Pain (LBP) is more cost effective than the two other interventions studied.

Participants were recruited through the occupational health services and by advertisement in the local press. Study subjects eligible for inclusion were informed of the study either by health care personnel at the occupational health care centers or by a research assistant at the Karolinska Institutet. Subjects were informed that if they were eligible to participate in the study they would be given the opportunity to participate in one of three approaches for treatment of neck and back pain.

The study was a randomized control trial with a 12-month follow-up that compared active early intervention using medical yoga with exercise therapy and self-care advice. The medical yoga intervention was a standardized program based on Kundalini yoga. The group was led by an experienced yoga instructor. The exercise therapy was a standardized strength training program led by a trained physiotherapist. Both medical yoga and exercise interventions were held in groups and included two sessions per week over six weeks. After the sixth week, participants were instructed to continue practicing at least twice a week on their own. In the medical yoga group, the participants received written information and a disk providing additional guidance. In the exercise therapy group, the participants received tailored written information on exercise. The third group, evidence-based self-care advice, was physically examined by experienced back pain experts (an orthopedic specialist and a licensed chiropractor), and received an oral recommendation to stay active and a booklet containing evidenced-based self-care advice.

The participants were randomized to one of these three treatment groups after undergoing the initial examination and receiving the evidence-based information on self-care and staying active. The form of randomization was block randomization using the pre-randomization technique, in which for each participant an opaque envelope was picked, in consecutive order, by an external research assistant who had no contact with the participants. After randomization the back pain specialist met with the participants and gave them background information about the intervention they were being offered. Previous studies [19, 20] have shown that expectations of treatment and response levels differ depending on, whether the treatment is physically or psychologically oriented. Therefore, the two training interventions (yoga and exercise therapies) were both presented as well established training therapies, to improve the level of participation and to equalize the participants' expectations of the treatment and its outcomes. After the assignment of study participants to intervention groups, the statistician who performed the analyses on the intervention outcomes was "blinded". This implies that the statistician while assessing the outcomes of the interventions was not aware of the assigned intervention of participants and therefore, was not influenced in any way by the knowledge of which group was the intervention or the control.

Ethical consideration All three groups received treatments based on ethical grounds. The study was approved by the Regional Ethics Committee (2010/108-31/3) and registered in the clinicaltrials.gov protocol registration system (NCT01653782).

Data collection Participants were recruited through the Occupational Health Services (OHS) and by advertisement in the local media in Sweden's Stockholm County. People of working age with neck/back pain were invited to apply for participation in the study. Then, a screening questionnaire was mailed to those who responded to the invitation to participate in the study. Those who scored 90 points or more, i.e., fulfilling the requirements for a yellow flag, on the Örebro Musculoskeletal Pain Screening Questionnaire (OMPSQ) [25] were invited for further physical examination.

The inclusion criteria were having non-specific low back pain, being with the age range of 18-60, having scored 90 points or more on the OMPSQ screening questionnaire and having a sufficient command of Swedish. The exclusion criteria were pregnancy, comorbidities that could affect the ability to perform exercise, ongoing regular weekly yoga practice or strength training and ongoing sickness absences of eight weeks or more.

Inclusion Criteria:

• non- specific low back pain,
• 18-60 years old,
• > 90 points on the OMPSQ screening questionnaire for yellow flags and sufficient understanding of the Swedish language

Exclusion Criteria:

• presence of so called Red flags,
• pregnancy,
• comorbidities affecting the ability to perform the interventions,
• presently on sick leave for > 8 weeks,
• ongoing regular weekly yoga practice or strength training.

Serious and Other (Not Including Serious) Adverse Events were not collected/assessed.

Problems in recruiting eligible subject and drop outs especially in the control group resulted in a small number of subjects analysed.