## 5 Discussion  
This study's objective was to assess the effects of self-selected intra-complex rest interval on CMJ and standing spike attack performance after the pyometric CA. This study showed that a pylemetric CA with a self-selected intra-complex rest interval failed to elicit localized and non-localized PAPE effect in a group of sub-elite volleyball players. Moreover, results of the present investigation showed a negative trend in the attack jump (decline in \begin{table}
\begin{tabular}{c c c c} \hline \hline
**BA** & **Post-CA** & **ES** & **RE [\%]** \\ (95 CI; Median [IQR]) & **(95 CI; Median [IQR])** & **ES** & **RE [\%]** \\ \hline \multicolumn{4}{c}{Jump Height [cm]} \\ \hline \(49\pm 5\) & 47.4 \(\pm\) 6.7 & \(-\)0.27 & \(-\)2 \(\pm\) 19.2 \\ (48.7 to 52.3; 46.5 [8.2]) & (42.9 to 51.9; 45.9 [6.3]) & \(-\)0.27 & \(-\)2 \(\pm\) 19.2 \\ \hline \multicolumn{4}{c}{Relative Mean Power Output [W/kg b.m.]} \\ \hline \(47.\) \(3\pm 9.5\) & \(43.4\pm 7.2\) & \(-\)0.46 & \(-\)5 \(\pm\) 25 \\ (40.8 to 53.6; 48 [17]) & (38.6 to 48.3; 43.2 [10.5]) & \(-\)0.46 & \(-\)5 \(\pm\) 25 \\ \hline \multicolumn{4}{c}{Ball Velocity [km/h]} \\ \hline \(72.9\pm 6\) & 68.6 \(\pm\) 5.9 * & \(-\)0.72 & \(-\)6 \(\pm\) 7 \\ (68.9 to 76.9; 75 [7]) & (64.7 to 72.6; 68 [10]) & \(-\)0.72 & \(-\)6 \(\pm\) 7 \\ \hline \hline \end{tabular}  
*BA—baseline; CA—conditioning activity; ES—effect size; RE—relative effect; CI—confidence interval; IQR—interquartile range; b.m.—body mass; *\(p\) < 0.05 significant different from the baseline.  
\end{table} 
Table 2: Baseline and post-CA performance. Figure 1: Individual choice of intra-complex rest intervals by the volleyball players participating in the study. height by \(\sim\)2% and in relative mean power output by \(\sim\)5%), as well as a significant decrease of ball velocity during the standing spike attack (by \(\sim\)6%). Several reasons may explain the lack of performance enhancement observed in the protocol of this study. First, the participants in our study self-selected average intra-complex rest intervals of 262 \(\pm\) 66 s for the attack jump and 197 \(\pm\) 110 s for the standing spike attack (Figure 1); however, as shown by [PERSON] and [PERSON] [19], intervals above 5 min are needed to enhance a greater PAPE effect than a shorter rest interval. In the case of the study by [PERSON] et al. [27] in which the half squat exercise improved the countermovement jump performance with self-selected intra-complex rest intervals, the participants chose a longer rest interval time of 357 \(\pm\) 164 s. It can therefore be assumed that the PAPE effect was not elicited because most likely fatigue exceeded the accompanying potentiation caused by the CA applied. Secondly, this is the first study on female athletes using self-selected intra-complex rest intervals in PAPE protocols, while previous studies were carried out on males. Sex differences in muscle fatigue have been suggested before, with females generally exhibiting a greater relative fatigue resistance than males [33]. Therefore, females may also show a different level of perception of fatigue from males; however, this is speculation and therefore further studies are warranted. Third, the participants in the [PERSON] et al. [27] study showed significantly higher levels of relative muscle strength (\(\sim\)2.4) than those in the [PERSON] et al. [28] study (\(\sim\)1.9 kg/kg body mass (b.m.) as well as ours (\(\sim\)1.16 kg/kg b.m.) in the half back squat exercise. [PERSON] and [PERSON] [19] showed that the level of muscle strength has a significant impact on the magnitude of the PAPE effect, stating that the stronger (above 1.75 kg/kg b.m. for men and 1.5 kg/kg b.m. for women in the back squat) show a greater response than the weaker ones (below 1.75 kg/kg b.m. for men and 1.5 kg/kg b.m. for women in back squat). It seems that the participants of this study failed to reach the moment in which the performance enhances after the CA. This study raises another intriguing issue, the non-localized PAPE phenomenon.