The goal of this clinical trial is to investigate the effectiveness of yoga for patients with chronic low back pain and high risk of poor prognosis. The main question it aims to answer is:

- In patients with back pain and high risk of poor prognosis, what is the effectiveness of yoga plus education on reducing pain and disability compared to a control group receiving education alone?

A total of 110 patients with chronic low back pain and classified as high risk of poor prognosis according to the Orebro Musculoskeletal Pain Screening Questionnaire (i.e. score ≥ 50 points out of 100) will be recruited for this study. Participants will be randomized into two groups: yoga and control. The yoga group will receive a 3-month course of yoga program consisting of two sessions per week and 3 educational classes. The control group will receive 3 educational classes over a 12-week period. Outcome measures will be assessed at baseline, at post-intervention (i.e. 3-months post randomization) and at 6-month follow up (i.e. 6-months post randomization).

Inclusion Criteria:

• report chronic nonspecific LBP, defined as pain and discomfort localized below the costal margin and above the inferior gluteal folds, with or without leg pain and of at least 3 months' duration.
• score ≥ 50 points (out of 100) in the Orebro Musculoskeletal Pain Questionnaire.
• have an average back pain intensity of 3 points or more on a 0-10 numerical pain rating scale.

Exclusion Criteria:

• serious spine pathology (e.g. tumors, fractures, and inflammatory diseases).
• nerve root compromise (i.e. at least 2 of the following signs: weakness, reflex change, or sensation loss associated with the same spinal nerve).
• previos spinal surgery.
• pregnancy or having given birth within the previous 3 months.
• any medical condition that prevented being physically active (e.g., serious cardiovascular, kidney or neurological diseases).
• any other musculoskeletal condition that may affect activity and movement participation in a Yoga program during the last year.
• not currently receiving other physical activity-based intervention (e.g., Pilates, physical therapy, aquatic exercise).
• inadequate Portuguese literacy for the study's questionnaires and instructions.

The data of this study will be available from the principal investigator upon reasonable request.