## 1 Introduction  
Increases in strength, speed, and power are among the primary objectives in many sports disciplines [1; 2; 3; 4]. In collision sports, such as rugby and American football, these improvements are of utmost importance, as the majority of sport-specific tasks (e.g., tackling, trucking, and scrumming) heavily rely on high levels of these physical capacities [3; 5; 6]. In this context, throughout the annual season, a substantial portion of the physical training routine in these sports is composed of strength, speed, and power training sessions [7; 8; 6]. However, despite this priority, variations in these independent measures of athletic performance (e.g., speed and power) tend to be minimal or even nonexistent in elite players [3; 9], leading to a constant search for novel and more effective training strategies. While the majority of these processes are focused on investigating distinct training programs and their mid- or long-term adaptations in physical and technical performance, there has recently been a growing interest in examining the potential effects of acute enhancements that can be promoted by certain types of conditioning activities (i.e., CAs). In the literature, the term commonly used to describe this phenomenon is \"post-activation performance enhancement\" (PAPE), which refers to improvements in performance achieved during voluntary activities (e.g., a short sprint or a jump trial) after a CA [10; 11]. For this purpose, a myriad of exercises and methods (e.g., loaded and unloaded jumps, resistance exercises, and resistance sprints) are frequently used by coaches and sport scientists with athletes from various sports. Specifically for rugby--a team sport that requires exercises and techniques that can be applied quickly and simultaneously to multiple athletes [6; 12; 13]--only a few studies [14; 15] have examined the acute effects of different CAs. In one study [14], the authors found no effect of either heavy hip thrust or back squat exercises on short sprinting capacity (i.e., 5-10 m). More recently, another study [15] identified that heavier (50% 1 RM) but not lighter (30% 1 RM) jump squats promoted greater muscle stiffness during drop jumps (DJs). Therefore, more studies examining the effectiveness of alternative CAs on the specific performance of rugby players are warranted. In this regard, a series of previous studies support the use of various types of vertical jumps (e.g., sequential countermovement jumps [CMJs] or drop jumps [DJs] [16; 17]) and isoinertial exercises (e.g., isoinertial squats or deadlifts [18; 19]) as effective methods for improving speed- and power-related performance in athletes and individuals with diverse training backgrounds. For example, a randomized crossover study compared the effects of two different PAPE protocols (i.e., 3 sets \(\times\) 6 reps of traditional half squats or isoinertial flywheel [FW] squats), conducted one week apart, on the squat jump performance of physically active students [20]. Although both protocols were executed at the load that maximized power output, only the FW squat demonstrated a PAPE effect on squat jump performance, as measured by jump height, velocity, and power [20]. Other studies (including reviews) [21; 22; 23; 24; 25] have already identified acute increases in subsequent physical performance tests (e.g., jump, directional changes, and sprint measurements) and in a range of kinetic and kinematic parameters, such as force, impulse, power, and acceleration rate, following the use of various types of FW eccentric-overload (EOL) exercises. However, it is worth noting that some authors have highlighted important points related to the CAs performed to induce PAPE, as well as the transient responses of these potential improvements. According to these authors, the kinetic and kinematic characteristics of the CA should be as similar as possible to evoke an enhanced effect on the succeeding motor task (e.g., FW squat and CMJ) [21; 24; 26; 27].