As mentioned above, this study was carried out to determine and compare the effectiveness of stabilization and McKenzie exercises on pain, disability and Transverse abdominis and multifidus muscle thickness in resting and contracting states in patients with nonspecific chronic low back pain. It was hypothesized that stabilization exercises would increase the thickness of Transverse abdominis and multifidus muscles and that McKenzie exercises would not have any effects on the thickening of the Transverse abdominis and multifidus muscles.