Chronic non-specific low back pain (CNSLBP) has been defined as a persistent pain in the lower back for at least three months with no known causes. The CNSLBP prevalence is estimated of 90% among all types of the LBP. The LBP imposes high direct and indirect costs on the patients and the society. Whereas a specific pathology has not been identified for CNSLBP, mechanical factors (e.g. changes in muscle length, strength, or endurance) may contribute to the pain and disability.

Inclusion Criteria:

• Patients with chronic non-specific LBP,
• LBP duration ≥ 6 months.

Exclusion Criteria:

• spinal osteoarthritis,
• spondylolisthesis,
• history of vertebral fractures.

Patients with chronic non-specific LBP were recruited from five hospitals in Ahvaz, Iran.