###### Abstract  
The purpose of the present study was to investigate effect of post-activation performance enhancement (PAPE) induced by the eccentric half-squat exercise on vertical jump performance in male jumpers. The jumping height, peak power, and work were measured and evaluated in twenty male jumpers (age: \(21.2\pm 1.7\) years, height: \(191.1\pm 3.3\) cm, body mass: \(81.56\pm 7.3\) kg) who participated in the national championship last year. Participants performed five eccentric half-squats at 85% of their one-repetition maximum (1 RM), with a knee angle below \(90^{\circ}\), followed by immediate and 2 min delayed jump assessments using the Squat Jump (SJ) and Countermovement Jump (CMJ) tests. Results showed that this specific PAPE protocol did not significantly improve jump performance for the SJ (Height: ES = 0.613, \(p\) = 0.462, Work: ES = 0.124, \(p\) = 0.231, Power: ES = 0.382, \(p\) = 0.125) or CMJ (Height: ES = 0.523, \(p\) = 0.368, Work ecc: ES = 0.133, \(p\) = 0.505 (only main effect time \(p\) < 0.05), Work con: ES = 0.114, \(p\) = 0.101, Power ecc: ES = 0.134, \(p\) = 0.177, Power con: ES = 0.182, \(p\) = 0.195, Leg stiffness: ES = 0.095, \(p\) = 0.358) tests. Factors such as stimulus specificity, rest intervals, muscle length, and the balance between potentiation and fatigue may explain these results. This study highlights the complexity of PAPE responses and suggests that a single set of eccentric squats with a short rest may not improve jump performance in male jumpers. Further research is required to optimize the interplay between conditioning stimuli and rest periods to maximize PAPE effects in athletic performance enhancement. post-activation performance enhancement; eccentric half-squat; squat jump; countermovement jump; jumping height; rest 2020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020220202020202020202020202202 and male adolescent soccer players showed a significant improvement in repeated sprint performance after performing loaded back squats [8]. Even in young female soccer players, combined balance and strength training acted as an effective PAPE stimulus to enhance jumping performance [9]. These findings highlight the potential impact of PAPE on sports activities with high power demands. The importance of power and work production, coupled with the levels of leg stiffness during an athletic performance, has been previously described [10; 11; 12; 13; 14]. Power production in eccentric and concentric phases has been described as a determined factor in the final jumping performance [15; 16]. The ability to rapidly produce high levels of force is directly linked to the capacity for work, allowing athletes to execute powerful jumps. The optimal level of leg stiffness ensures the proper transmission of the body from the eccentric to the concentric phase of the stretch-shortening cycle, leading to an efficient transfer of the produced work [14; 17]. However, despite the importance of these parameters to the jumping performance, the final jumping height seems to be the best indicator of an optimal use of the produced force and an efficient transmission of produced power and work. Given the above, the analysis of the kinetic parameters provides important insights into the jumping performance; however, the final jumping height seems to be the best indicator of an optimal jump. Isometric exercises have been effective in triggering PAPE responses, especially in individuals with high-strength capabilities [1]. A previous study suggested that 15 short, intermittent, and repetitive maximal voluntary contractions (MVCs) provide the most effective isometric stimulus to induce PAPE [18]. A 3 \(\times\) 3 s stimulus of an isometric half-squat led to increased jumping performance due to a greater rate of force development in trained individuals [1].