Context: Inappropriate activation of the anterolateral abdominal muscles affects the stability of the lumbopelvic zone and increases the appearance of pain and lesion in the area. Therefore, ways to improve its effective contraction are crucial in rehabilitation. The aim of this study was to compare the activation of the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles in 3 different pelvic positions (down pelvis [DP], horizontal pelvis [HP], and up pelvis [UP]) during sling bridge exercise (SBE) to determinate which position is more effective to promote a correct contraction of the anterolateral abdominal muscles. Design: Cross-sectional study. Methods: Fifteen participants performed 3 variations (DP, HP, and UP) of a one-legged exercise called “supine pelvic lift” on a sling device. The thicknesses of the TrA, IO, and EO were recorded at rest and at the 3 positions using ultrasound imaging. Thickness, change ratio, lateral slide of TrA, and preferential and contraction activation ratio of TrA, IO, and EO were analyzed. Results: TrA and IO showed greater activation (P = .01) in the UP position than the other pelvic positions. In addition, UP position decreased the activation of the EO (P = .01). Conclusion: Based on the results of this study, SBE in the UP position has the potential to improve normal contraction patterns of the musculature and can be used in future intervention of the lumbopelvic zone.