Background: Most papers examining the lateral abdominal muscles (LAMs) and low back pain (LBP) are cross-sectional,with groups of participants being divided into a control and an LBP group.We hypothesized that morphological measurements of the LAMs in adolescent soccer players may predict future LBP incidence.The aim of this study was to examine the associations between the morphology of LAMs and LBP incidence rate among adolescent soccer players.Methods: Ninety-seven adolescent male soccer players with no LBP at baseline were recruited into the prospective cohort study.The thickness of the LAMs was measured at baseline by ultrasound imaging in a supine rest position.Nine cases of LBP occurred during the follow-up 6-month observation.Results: An obliquus internus (OI) asymmetry was related to increasing LBP risk (odds ratio =19.99;95％CI: 2.4-167.9).Spearman correlation also showed a linear relationship between OI asymmetry value and duration of LBP (R =0.75,p =0.02).An OI side-to-side difference greater than 1.25 mm suggests possible LBP incidence in the 6-month observation among adolescent soccer players.Conclusion: The morphological changes of the OI may be related to LBP's incidence in adolescent soccer players.The presence of OI asymmetry increases the odds of LBP by at least 2.4 times.Hypertrophy of the OI on one side of the body may contribute to trtnk muscle imbalance.