## 4 Discussion  
The present study aims to analyze the role of the [PERSON] method and Isostretching on CMJ performance in rhythmic gymnasts with LBP. All variables exhibit large or very large effect sizes, indicating that the [PERSON] training had a substantial impact on jump performance and efficiency over time. Specifically, CMJ Maximal Force (\(\eta^{2}\) = 0.672) showed a large effect, suggesting significant strength improvements. CMJ Concentric (\(\eta^{2}\) = 0.170) and CMJ Excentric (\(\eta^{2}\) = 0.375) variables also displayed large effects, highlighting enhanced force production in both phases of the jump. Additionally, CMJ Flight Time (\(\eta^{2}\) = 0.440) and CMJ Contact Time (\(\eta^{2}\) = 0.521) demonstrated notable changes, pointing to improved jump mechanics and power application. The most pronounced effect was observed in CMJ VAS (\(\eta^{2}\) = 0.896), indicating a very large reduction in pain perception, reinforcing the method's effectiveness in addressing low back pain while enhancing gymnastic performance. The analysis demonstrated that both interventions significantly reduced low back pain intensity, as measured by the Visual Analogue Scale (VAS). However, gymnasts in the Mezieres group showed a slightly greater reduction in pain scores compared to those in the Isostretching group. These findings align with previous research emphasizing the benefits of postural re-education and myofascal elongation techniques [11]. Given that the Mezieres method primarily focuses on global postural correction and muscle chain stretching, it may offer superior relief by addressing underlying musculoskeletal imbalances contributing to chronic pain. Although both groups exhibited improved core stability and strength, the Isostretching group showed a more pronounced increase in core endurance. Since core engagement plays a critical role in jump mechanics, force transfer, and eccentric control, the observed improvements in maximal speed, maximal height, Maximal Force, and Concentric-Eccentric Exercise Performance parameters could be explained due to neuromuscular efficiency and stabilizing muscle activation improvement. The observedimprovements suggest that postural interventions, particularly Isostretching, may enhance neuromuscular efficiency by promoting better activation of stabilizing muscles. These results correspond with findings from [PERSON] et al. (2023), which highlight the importance of core stability in enhancing gymnastic performance. The Isostretching technique, which emphasizes controlled breathing and muscle activation, may have facilitated more efficient neuromuscular engagement, leading to better stabilization of the lumbar region [25]. While the [PERSON] method showed substantial effects on CMJ metrics, including Maximal Force (\(\eta^{2}\) = 0.672) and flight time (\(\eta^{2}\) = 0.440), the improvements were more focused on flexibility and pain reduction rather than explosive power. [PERSON] et al. (2024) reported that cluster-based pyometrics specifically optimized neuromuscular coordination and rapid force development, which might offer superior benefits for gymnasts requiring quick, explosive movements [26]. However, the [PERSON] method's advantage in reducing CMJ VAS (\(\eta^{2}\) = 0.896) suggests that it provides better pain management, which is critical for long-term athletic performance and injury prevention. A combined approach integrating both methodologies could maximize performance gains while ensuring injury resilience. Functional movement improvements were assessed through standardized gymnastic performance tests, including vertical jump and dynamic flexibility assessments. Athletes undergoing the Mezieres method displayed an enhanced range of motion, particularly in spinal mobility and hamstring flexibility. These findings are consistent with those reported by [PERSON] et al. (2020), who indicated that flexibility gains contribute to better biomechanical efficiency during jumps and landings [27].