Context: One of the main reasons why athletes with a high physical condition suffer from low back pain disease is because they often participate in sports that involve disc compression movements during flexion, lifting loads, or torsion movement. Objectives: This study aims to examine the effectiveness of the postural treatment of the Mezieres method on elite rhythmic gymnastics athletes with low back pain. Design: Double-blind, randomized, controlled trial. Setting: The sports hall of "Puente Tocinos," Murcia, Spain. Participants: Ninety gymnastics athletes were randomized into 2 parallel groups (intervention: n = 39; control: n = 51), of whom 98.9% were women (women = 89; man = 1). Intervention: The Mézierès method postural therapy was implemented. It lasted about 60 minutes in repeated sessions of 2 to 3 meetings per week by counting in overall 60 sessions during a 24-week period. Main Outcome Measures: Visual analog scale of pain, sit and reach flexibility test, Runtastic (pedometer performance android application), Roland-Morris Questionnaire for the physical disability, and the Health Status Questionnaire were used. Results: The univariate analysis of variance and independent sample t test revealed a significant improvement in the intervention group concerning the visual analog scale pain assessment scale (P < .05, ηp² = .625), and, also, the between-groups effect size was high during the 24 sessions of treatment (d > 0.8) compared with the control one. The same situation persists even for Roland-Morris Questionnaire (P < .05, ηp² = .802), physical score (P < .05, ηp² = .613), mental score (P < .05, ηp² = .736), sit and reach flexibility test (P < .05, ηp² .666), and Runtastic performance (P < .05, ηp² = .790), where the between-groups effect size was high during the 24 sessions of treatment (d > 0.8). Conclusion: The Mézierès method treatment performed on athletes with low back pain has caused positive effects on all the outcomes analyzed compared with the ones of control group. [ABSTRACT FROM AUTHOR]