there was high intra-tester reliability for the ultrasound measurements of the multifidus and Transverse abdominis muscle thicknesses at rest and during contraction (ICCs= 0.87 to 0.96). To measure the thicknesses of the multifidus and Transverse abdominis muscles, a B-mode ultrasound apparatus (MyLab 50 XVision, ESAOTE S.p.A, Genova Italy)