## 4 Discussion
Also, the groups were similar in terms of RASTmean (\(p\) = 0.99), RASTbest (\(p\) = 0.99), and RASTtotal time (\(p\) = 0.99). These results aligned with those of a prior study [14]. The previous study investigating the impact of the PAPE protocol on RSA in soccer players revealed that PAPE responses were more pronounced among elite soccer players. However, the researchers observed that individual differences among amateur athletes could obscure RSA performance [14]. A similar effect may have occurred in our study. On the other hand, the nonsignificant difference between the experimental conditions may be due to insufficient statistical power. The researchers reported that analyses without sufficient statistical power are prone to Type I error [42]. This study selected athletes with different competition levels for power analysis [14; 23]. The findings of previous studies may not apply to the present participants. The nonsignificant difference in the time-condition interaction may also be associated with the RAST responses of amateur athletes during the PAPE protocol. Although previous studies claimed that PAPE could improve RAST performance, it was reported to have a nonsignificant or negligible effect on amateur athletes [14]. Therefore, it was assumed that the absence of a significant difference between the groups in our study is consistent with the existing literature. This study was the first to examine the individual RAST responses of soccer players during PAPE protocols. Twelve soccer players exhibited varying RAST responses during PAPE. These results may suggest that the time-condition interaction leads to insignificant outcomes. It is well established that individual differences influence the PAPE phenomenon [11; 12; 19]. Factors such as VO2 max, time constant, and physiological biomarkers may also impact the RAST performance of amateur soccer players [43; 44]. These variables create limitations in accurately assessing the effect of PAPE on RAST performance. This study has several limitations. The first limitation pertains to the rest period. Researchers have reported that individuals with high strength experience the greatest PAPE effect after 5 to 7 min of preload, while those with lower strength require at least 8 min of recovery [45]. Since the current study implemented a 5 min rest period for PAPE in weaker individuals, future research could evaluate the effects of PAPE on the RAST with longer rest intervals. Additionally, male amateur soccer players with low strength levels were included in this study. The study protocol could also be applied to soccer players with higher strength levels. Beyond the factors influencing the PAPE phenomenon, numerous mediating variables can affect RAST performance in team sports [46; 47; 48; 49; 50]. This study determined that mediators such as heart rate and perceived exertion did not significantly impact performance. However, future studies could assess mediating variables such as VO2 max and blood biomarkers to understand the relationship between PAPE and the RAST better. Finally, movement speed may also influence preload protocols [50]. Therefore, future research could confirm the effects of performing half squats versus full squats and the outcomes of varying the number of sets and types of exercises. The current study included a sample of 18 amateur male soccer players. This sample may not be sufficient to prove the global effectiveness of an intervention targeting the physical performance of soccer players. Therefore, this study can be repeated with larger sample groups.