## 4 Discussion  
For the first time, we examined the effects of two novel PAPE protocols, comprising FW squats vs. DJs, on the power- and speed-related performance of elite rugby players. Additionally, we compared the variations in muscle mechanical properties, as assessed by TMG, induced by both protocols. Despite using two CAs that have already demonstrated their effectiveness in previous research [10; 16; 18; 21; 30], we did not observe any significant changes in the range of variables considered in this study. Therefore, our initial hypothesis, suggesting that DJ exercises could be more effective and faster in producing acute improvements in speed- and power-related capacities, was not confirmed. This is likely because, for these highly trained athletes, the volume of exercises provided as CAs was insufficient to elicit positive changes in their physical performance [21; 43]. Overall, various types of jump exercises (e.g., vertical and horizontal DJs, CMJs, squat jumps, standing long jumps, etc.) are regularly used by coaches and practitioners to induce positive PAPE responses in athletes across various sport disciplines (e.g., track and field, handball, rugby union, hurling, etc.). For example, [PERSON] et al. [17] verified that the simple inclusion of continuous CMJs as CAs (three sets of five CMJs with a 1 min rest interval between sets) in the regular warm-up routine of national-level spriternes increased their 30 m sprint speed 2 and 4 min after the execution of the jumps. In the same vein, [PERSON] et al. [43] applied an extensive and varied pylemetric PAPE protocol that included 2 sets of 10 ankle hops, 3 sets of 5 hurdle hops, and 5 depth jumps from a height of 50 cm (totaling 40 jumps) to a sample of professional rugby union players and observed significant improvements in CMJ height at 1, 3, and 5 min after completing the CAs. Two studies using only DJs, with or without additional loads, were also able to promote significant increases in CMJ height or sprinting speed [44; 45]. In the first study, strength-trained athletes performed one set of five DJs from their optimal drop heights with no additional load and with extra loads (i.e., dumbbells) equal to \(10\%,20\%\), and \(30\%\) of their body mass before completing three CMJs following recovery periods of 2, 6, and 12 min. After analyzing and comparing all CAs, the authors concluded that the greatest subsequent CMJ performance was achieved utilizing an extra load of \(20\%\) of body mass at the 2 min interval. Similarly, in an investigation involving high-level sprinters, [PERSON] et al. [44] found significant improvements in the CMJ and 50 m sprint performances after completing a CA consisting of two sets of five DJs from a 75 cm box, with a 3 min rest after each set. Therefore, it is difficult to explain why our players, regardless of their playing positions, did not show significant improvements in any of the speed-related variables (i.e., 10 m sprint, 30 m sprint, and COD speed). Compared with the aforementioned studies, perhaps the use of a fixed drop height (45 cm) instead of an \"optimal drop height\" (determined by the reactive strength index [RSI], for example) [10; 46] or the execution of only a single (rather than multiple) set(s) of DJs, may have negatively influenced the results, making this stimulus ineffective for the vast majority of the group. These hypotheses should be tested in future studies examining PAPE responses not only in rugby players but also in athletes from other team sports. Flywheel exercises have been extensively investigated in recent years, showing promising results in terms of PAPE responses [18; 20; 21; 26]. An interesting study compared the