The relevance of this study is given by the feasibility to assess the effect of an intervention program based on the postural control and trunk neuromuscular activity, comparing two methods: stabilization exercises vs. back strengthening exercises, in athletes with low back pain. The main outcomes will be computed by electromyography measurement so that to assess the trunk neuromuscular activation pattern as well as by force platform parameters for determining of postural control. Clinical symptoms such as pain intensity, perception of disability and fear and avoidance will also be computed. This is the first study to compare two intervention methods using the main biological outcomes related to trunk neuromuscular function.

For this study, a proposal of a 8-week intervention program will be carried out with lumbar stabilization exercises and back strengthening exercises, in 32 athletes with chronic low back, recruited by convenience and voluntaries from the community local and sports centers. Before intervention, all participantes will be evaluated by: electromoyography during back endurance and strength tests, balance performance, physical capacity, and by clinical outcomes such as pain, disability and psychological factors. All baseline testing and evaluation will be performed by a blinded evaluator to the study intervention. Afterwards, the participants will be randomized in two groups by a blinded evaluator (people not enroled to study): G1: exercises for lumbar stabilization; and G2: strengthening exercises. The intervention will follow 8 weeks, with 50 minutes of duration each session of therapy including measurement of blood pressure, heart rate and the Visual Analogue Scale (VAS) before and after each session, and the perception of exercise intensity monitored by Borg Scale. Within this proposal, the exercise sessions will performed twice a week. The intervention will follow the CONSORT recommendations for randomized controlled trials. The intervention will start in: G1 (n=16, motor control group), which will perform therapy with specific exercises for lumbar stabilization including the Swiss ball as therapeutic resource; while G2 (n=16, strength group) will perform back endurance progressive and resisted exercises on a Roman chair. The participants will not be blind to the study due to the characteristic of the exercises that often reflect to the improvement of the symptoms. In case of eventual losses, the intention-to-treat method will be used for the analyses. After the intervention, all groups will be invited to come back to the laboratory to proceed the same evaluation from baseline (trunk activation during exercises, balance, and clinical outcomes). For the analysis two-way ANOVA with repeated measures will be performed to compare the effects of the intervention (two groups) and times (baseline vs. end 8-weeks measurement) and the effects of interaction (Groups x Times). The size effect also will be computed to determine the rate of the changes observed.

Inclusion Criteria:

• chronic low back pain at least for three months, in a unique or multiple episodes.
• low back pain of unknown origin and mechanical nature.
• athletes must be train or play five times in a week.
• athletes must be participate in some official competition.

Exclusion Criteria:

• previous surgery (locomotor appareil).
• discal herniation diagnosis.
• nerve root entrapment.
• spondylolisis.
• spondylolisthesis;
• lumbar stenosis.
• hip cartilage damage.
• labral injury,
• piriformis syndrome.
• neurological disease.
• no current treatment in Physiotherapy or Pilates or Manual Therapy.