Nowadays, the research priority in low back pain area have been find subgroup of patients with the same characteristics that might achieve better outcomes in a specific intervention. However, even though the studies in this area have increased, questions of this nature remaining without an adequate answer, or with limited evidence. Therefore, the investigators propose to examine the ability of clinical tests, developed to assess alterations related to clinical lumbar instability, to identify subgroups of patients with non specific chronic low back pain that may have better outcomes after a motor control exercises intervention.

Changes relative to clinical instability are well established in individuals with non specific chronic low back pain. However, in this population, these changes vary widely, characterizing them as an heterogenous group. Motor Control Exercises (MCE) aims to improve the impaired coordination of deep and superficial muscles of the trunk, to reestablish the stability of the lumbar spine reducing the common alterations in this population, and are associated with reduction of pain and disability of patients with non specific chronic low back pain. To specific assessment of the changes found in this population, clinical tests are often used: in the assessment to identify motor control alterations; during intervention as parameter for treatment progress (e.g. to increase exercises difficulty); and after intervention, to ensure that there was normalization of the motor control. There are several clinical tests to assess changes relative to clinical instability, such as: Clinical Classification Scale (CCS) to assess abdominal muscles and the coordination between superficial and deep trunk muscles; Clinical Test of Thoracolumbar Dissociation (CTTD) to assess anterior/posterior tilt while maintain a constant position of thoracolumbar junction; and the Prone Instability Test (PIT) and Passive Lumbar Extension Test (PLET) used to detect structural lumbar instability.

Therefore, primary objectives of this study are: to investigate the ability of clinical tests in predict clinical outcomes, pain and disability, in motor control exercises program, and to investigate the association of two or more tests to predict clinical outcomes.

Inclusion Criteria:

• between 18 and 60 years.
• non specific chronic low back (pain for more than 3 months) with pain intensity of at least 3 points measured by pain numerical rating scale (0-10) and disability of at least 6 points in the 24-item Roland Morris Disability Questionnaire (0-24).
• classified as low or medium risk though StarT Back Screening Tool

Exclusion Criteria:

• cardiovascular and neurological pathologies
• serious pathology in the spine and pelvic.
• previous spinal surgery of at least 1 year before the trial period.
• check-list with the red flags was performed to exclusion
• classified as high risk through StarT Back Screening Tool, due these patients have high psychological components and needed of specialized psychological attendance