Effects of a Protocol of Hip Flexor Stretching on Chronic Mechanical, Non-specific LBP.

The goal of this clinical trial is to compare the effectiveness of a stretching, exercise and education protocol versus usual care in improving pain, function and disability in patients with non-specific mechanical chronic low back pain (CLBP). The research hypothesis is: A combination of hip flexors stretching, exercise and education is more effective than usual care to improve pain, function and disability in patients with CLBP. Participants will be randomly allocated in one of the two treatment groups. Pain, function and disability will be assessed before starting treatment, after the end of the treatment and one month , three months and one year after the end of the treatment.