# Effects of Post-Activation Performance Enhancement on Jump Performance in Elite Volleyball Players
## 4 Discussion
Much longer rest periods were originally suggested to induce a PAPE effect (7-10 min by [PERSON] et al. [2]), especially for vertical jump performance (3-7 min by [PERSON] et al. [37]). This may explain why some of the participants were categorized non-responders in this study. Conclusions of previous studies [2; 26; 37] indicate that using the same CA parameters and different rest intervals (reduced or extended) may be appropriate to induce PAPE in elite volleyball players. Therefore, in future research other variables could be adjusted to optimize PAPE in elite volleyball players, i.e., by solely manipulating rest intervals between CA and an explosive exercise and either keeping CA or parameters constant or manipulating them as well. A possible explanation for the higher efficacy of CA in SJ than CMJ is the specific range of motion of a trap bar deadlift, which is similar to that of SJ. According to [PERSON] et al. [38] the range of motion of the CA has a significant effect on the magnitude of the PAPE response, with the most considerable effect achieved when the range of motion of the CA is similar to that of the subsequent explosive task. In the present study, the depth of SJ was set to approximately 90 degrees of knee flexion, whereas the depth of CMJ was individual determined for each athlete. Analysis of the biomechanics of a trap bar deadlift revealed 78.8 \(\pm\) 11.2 degrees of knee flexion in the starting position [39]. Taking into consideration that every athlete likely did not perform the SJ with exactly 90 degrees of knee flexion, as we did not measure this value with a device, it could be debated whether the level of knee flexion is similar between SJ and a trap bar deadlift. It has been proven that when performing CMJ, countermovement depth affects vertical jump performance [40; 41; 42; 43; 44; 45]. As the athletes in the present study self-selected countermovement depth and this parameter was not measured using a device, we speculate that CMJ depth could play a role in the achievement a potentiation response after CA. Therefore, in the future, researchers should consider first measuring CMJ depth of an individual and then prescribing an appropriate squat depth or height of the bar lifted from the floor to achieve a similar level of knee flexion, possibly inducing PAPE more effectively. A possibly explanation as why participants turned were either responders or non-responders is a somatic component expressed in the body height. As previously mentioned, the accommodating resistance used in the present study was an elastic band with approximately 25 kg band tension, amounting to 18 \(\pm\) 2% of 1 RM in CA. Therefore, the use of the same band for all participants rather than choosing a distinct band for every participant to achieve the intended percentage of 1 RM may have influenced the results of the present study. For taller participants, the band provides more tension during the concentric phase, as it stretches for a greater distance, likely resulting in a 1-2% difference in 1 RM. Participant mean body height in CMJ was 194 \(\pm\) 6.8 cm for responders and 195.3 \(\pm\) 4.9 for non-responders; in SJ, mean body height 195.8 \(\pm\) 5.7 for responders and 193 \(\pm\) 5.9 for non-responders, suggesting that the body height of the participants and the resulting differences in tension of the elastic band was not a limiting factor that could have influenced the results of the study. Additionally, volleyball position was not a limiting factor, as the players of every volleyball position were both responders and non-responders in both tests. Although the protocol applied in the present study was partially appropriate to induce PAPE in elite volleyball players, CA was more effective in terms of potentiating SJ than CMJ (8 of 11 players responded in SJ vs. 6 of 12 in CMJ). A possible explanation for this phenomenon is that performing SJ is more specific to a trap bar deadlift than performing CMJ.