## 4 Discussion
The predictive value of PSAP for mid-phase sprint distances (0-20 m and 0-30 m) indicates that elastic pre-tension contributes to sustained acceleration beyond initial propulsion. In this context, PSAP may serve as an indirect marker of stretch-shortening cycle efficiency, highlighting its role not only in vertical displacement but also in optimizing horizontal force application during prolonged sprint efforts. The link between musculo tendons stiffness and initial sprint acceleration highlights the importance of optimal elastic tension for rapid force transmission. During the first 10 m of sprinting where ground contact time is minimal, adequate stiffness enhances mechanical efficiency by reducing energy dissipation. Conversely, suboptimal stiffness may impair force application, resulting in reduced acceleration capacity. Therefore, stiffness should be considered a key neuromechanical quality in explosive locomotor tasks. Taken together, these findings highlight the significant impact of eccentric-phase characteristics on sprinting, vertical jump, and change of direction performance in female athletes. Therefore, these variables should be integrated into comprehensive performance profiling and individualized training strategies. The inclusion of athletes from various sports disciplines in this study suggests that sport-specific physiological and technical demands may have influenced performance outcomes. For instance, athletes from sports such as football, handball, and basketball are expected to perform better in sprint and change-of-direction tests due to the frequent need for rapid acceleration, deceleration, and re-acceleration in their sports. Conversely, vertical jump performance may be more pronounced in sports like volleyball and basketball, where vertical force production is a core component of performance. These differences highlight the potential influence of sport-specific training backgrounds, neuromuscular adaptations,and technical movement patterns on the measured parameters. Future studies may benefit from subgroup analyses based on sport type to provide more refined and contextually relevant interpretations. In contrast, no significant relationships were found between EUR and any performance variables in male athletes, indicating that EUR may be inadequate in capturing elastic energy utilization capacity in this group. This may be attributed to sex-based differences in neuromuscular, structural, and elastic characteristics. Female athletes tend to exhibit greater tendon elasticity, more compliant muscle-tendon architecture, and a higher reliance on passive elastic components, which may enhance elastic energy recovery during the eccentric phase [39, 40]. Conversely, higher absolute strength, muscle mass, and Type II fiber proportion in males may limit the explanatory capacity of ratio-based metrics like EUR [41]. Additionally, since EUR is calculated as the CMJ/SJ ratio, the typically higher SJ values observed in male athletes may reduce the relative difference between CMJ and SJ, resulting in lower EUR values. Consequently, EUR may not accurately reflect elastic energy efficiency in males. In contrast, the relatively lower SJ scores in female athletes allow for greater improvement in CMJ, which in turn results in higher EUR values and a more pronounced influence of the eccentric phase on performance. Moreover, high EUR values should not always be interpreted as indicators of superior performance. A recent study [9] reported that a student control group exhibited higher EUR values than all nine elite athlete groups involved in the research. The authors suggested that this outcome may have resulted from lower SJ performance in the control group, potentially reflecting lower rapid force development or greater muscle slack [19]. This implies that high EUR values may sometimes stem from artificially low SJ scores, rather than from high CMJ performance. Therefore, the CMJ/SJ ratio may inflate EUR in contexts where SJ is suppressed, leading to misleading interpretations.