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Background: The comparison between voluntary and automatic contraction of deep abdominal muscles in patients with Nonspecific Low Back Pain (nLBP) may the best treat for them. The aim of this case-controlled study was to compare changes in the thickness of the Transverses Abdomin is (TrA) and Internal Oblique (IO) muscles during the Abdominal Drawing-In Maneuver (ADIM) and the Active Straight-Leg Raise (ASLR) test. Methods: This study involved 30 women including 20 women with and 10 women without non-specific low back pain. The abdominal muscle thickness in the supine crook-lying, ASLR, and ADIM exercises were measured. Two-way repeated-measures ANOVA was used to compare the thickness ratio results between the two groups. Results: There were significant differences between the TrA (p < 0.05) and IO (p < 0.05) muscle thickness ratios during the ADIM compared to the ASLR in the neutral lumbar posture in supine lying in the healthy group; However, in the subjects with nLBP, only the TrA (p < 0.005) muscle thickness ratio was significantly higher in the ADIM rather than in the ASLR. Conclusion: These findings suggest that in both groups the deep abdominal muscles (the TrA and the IO) responded differently according to the variable type of activities such as voluntary or automatic, therefore, in training programs, in addition to a voluntary workout, automatic type of exercises should also be taught.