Mézières Method vs. Isostretching Postures on Countermovement Jump Performance in Elite Rhythmic Gymnasts with Low Back Pain: A Randomized Controlled Trial

This study aims to investigate the influence of the Mézières method and Isostretching postures on countermovement jump (CMJ) performance in rhythmic gymnasts with low back pain (LBP) by examining changes in jump height, movement efficiency, and pain perception. A randomized controlled trial (RCT) with a parallel-group design was conducted. Participants were randomly allocated into one of two intervention groups: the Mézières or the Isostretching group. Both groups underwent a total of 24 sessions. The Baiobit sensor was used as the primary assessment tool for measuring CMJ performance in elite rhythmic gymnasts with low back pain. A total of 17 rhythmic gymnastics athletes with LBP participated in the study. No differences were observed between groups in age, weight, or height; nevertheless, the Isostretching group had greater variability in age (SD = 4.82 vs. 0.91), while the Mézières group showed higher variability in height. As per maximal speed and height, the overall treatment effect was significant (p = 0.006, η2 = 0.431), indicating long-term benefits for Mezieres training, which also had a significant impact on CMJ Maximal Force, particularly at four sessions (p = 0.036), with improvements continuing over time (p = 0.003, η2 = 0.672). The Mezieres group showed higher force values compared to the Isostretching group at all time points. The results indicate that Mezieres training significantly improved CMJ Flight Time over time (p = 0.005, η2 = 0.440), with notable increases at all time points compared to the Isostretching group. Improvements were particularly evident in the 12th and 24th sessions, confirming its sustained effectiveness. CMJ Contact Time also showed a significant overall effect (p = 0.027, η2 = 0.521), with Mezieres training leading to greater reductions in contact time, particularly at 24 sessions (p = 0.003), highlighting improved efficiency in jump execution. Lastly, CMJ VAS (perceived exertion or discomfort) showed a significant overall effect (p < 0.001, η2 = 0.896), with Mezieres training leading to a progressive reduction in perceived exertion, particularly from eight sessions onwards, and the most pronounced effect at 24 sessions. The Mézières method and Isostretching postures offer substantial benefits for gymnasts with low back pain, though their mechanisms of improvement differ.