Purpose: This study was conducted to determine whether there are changes in the muscle thickness of the Transversus abdominis, Internal oblique, and External oblique muscles by applying the abdominal drawing-in while maintaining hip joint adduction using ultrasound. Methods: Thirty healthy adult men and women in their 20s located in J City were selected for the study. The participants performed the bridge posture while maintaining hip joint adduction, with the knee joint bending angle was set to 90° and 120°, and the abdominal drawing-in applied. The exercises were performed three times a week for a total of four weeks, and after applying exercise, the thickness of the Transversus abdominis, Internal oblique, and External oblique muscles were measured using ultrasound. After applying the exercise, the paired t-test was used to compare the effects of individual exercise training, and the independent t-test was used to compare the differences of each group. Results: The significance level was set at α<0.05. As a result of the study, the muscle thickness of the Internal oblique significantly increased during the 90˚ flexion of the knee joint (p>.05). Internal and External oblique muscle thickness significantly increased during the 120˚ flexion of the knee joint (p>.05). Conclusion: When the knee joint angle is 90° and 120°, with the bridge exercise in place, and the abdominal drawing-in applied, back pain can be prevented by selectively activating the Internal oblique External oblique muscles.