## 1 Introduction
Another issue to consider is the temporary and transitory nature of PAPE [10; 25; 28], which, regardless of the method or exercise used as the CA, could be ineffective during matches or even shorter competitions (e.g., certain track and field disciplines). In this respect, current evidence [10; 21; 28] may suggest that pyometric exercises, such as DJs, could exhibit a PAPE effect closer to the CA (e.g., \(<\)5 min) compared to other resistance exercises (e.g., flywheel EOL exercises, back squats, etc.) whose effects are more pronounced after 5 min of recovery. Another common type of CA utilized by athletes, especially in team sports, is jumping under loaded or unloaded conditions [29; 30; 31; 32]. Among these drills, the DJ unquestionably emerges as one of the most frequently used and studied exercises [16; 33]. In a study comparing different volumes and intra-repetition rest periods of DJs in 29 male hurling players competing at college and club levels, the authors reported that one set of three DJs, with individualized drop heights based on the reactive strength index (RSI, i.e., the ratio between jump height and ground contact time), and 15 s intervals between repetitions followed by a 15 s recovery after the last DJ, was effective in enhancing subsequent 20 m sprint speed [16]. [PERSON] et al. [33] also found positive results after examining the acute effects of vertical and horizontal DJs (VDJs and HDJs, respectively) on the physical performance of under-20 National Team handball players. Nevertheless, in that study, the acute effects on athletic abilities were retested 8 min after completing CAs composed of either three sets of five vertical-alternate single-leg DJs or three sets of five horizontal-alternate single-leg DJs, and the responses observed were very specific. While the VDJ condition induced greater changes in variables related to vertical jump performance, such as peak ground reaction forces (+ 9.6% vs. +1.3%) and RSI (+7.3% vs. +2.4%), the HDJ condition significantly improved the change-of-direction (COD) performance by reducing contact time (CT) during directional changes more than the VDJ condition (\(-\)13.3 vs. \(-\)22.4%, respectively) [33]. These results suggest that the HDJ condition is more effective at significantly reducing the CT of the \"plant\" step, thereby reinforcing the correlation between shorter contact times during deceleration maneuvers and superior COD techniques [33; 34; 35]. Other speed-related metrics, such as 25 m sprint speed, also exhibited a more substantial increase after executing the HDJ protocol compared to the VDJ protocol [33]. Together, these diverse effects may suggest that the nature and orientation of the CAs could be highly specific and should be prescribed according to the sport-specific tasks and their respective demands. However, this concept has not been consistently confirmed and requires further investigation [10; 33]. The primary aim of the current study was to examine the effects of two different CAs (i.e., FW EOL squats vs. 45 cm DJs) on the power- and speed-related performance of elite rugby players. Furthermore, as a secondary objective, to better understand and explain the potential changes in certain physical capabilities, we also analyzed the variations in muscle mechanical properties through the use of tensiomyography (TMG) after the execution of both PAPE protocols. We hypothesized that both protocols would be effective, but that the DJ protocol would enhance players' performance earlier than the FW protocol.