## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Variable** & **Pre** & **Post** & **t** & \(p\) & **Upper** & **Lower** \\ \hline Pain threshold & 7.6 \(\pm\) 2.4 & \
\begin{tabular}{c} 18.8 \(\pm\) \\ 23.9 \\ \end{tabular} &
\begin{tabular}{c} \(-\)2.625 \\ \end{tabular} & 0.014 & \(-\)20.12 & \(-\)2.45 \\ \hline Blood lactate (mmol/L) & 2.4 \(\pm\) 0.5 & 14.5 \(\pm\) 2.6 & \(-\)23.494 & \(p\) \(<\) 0.001 & \(-\)13.04 & \(-\)10.94 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Changes in perceived pain before and after the first and second HIIT series. enhancements are pivotal for improving endurance and have been widely corroborated by existing research [36]. Additionally, the post-HIIT rise in the rate of perceived exertion (RPE) offers a vital subjective perspective on the participants' perceived levels of exertion and the physiological stress endured. RPE serves as an indispensable tool for gauging the subjective intensity of the workout, where its elevation following HIIT sessions in this study reveals the substantial effort and energy participants invested in the regimen [37]. Expanding upon these findings, our study not only confirms the acute physiological impacts of HIIT but also sheds light on its effectiveness as a potent training modality. The observed metabolic and cardiovascular responses provide strong evidence of HIIT's capacity to foster significant physiological adaptations. These adaptations are instrumental in boosting athletic performance and elevating physical fitness levels. By engaging in HIIT, individuals can experience profound improvements in both their cardiovascular efficiency and metabolic function, underscoring the multifaceted benefits of this training approach. This comprehensive analysis emphasizes HIIT's dynamic role in advancing physical conditioning and enhancing endurance, positioning it as a key component of fitness regimens aiming to achieve optimal health and performance outcomes. The observed post-HIIT enhancement in muscular performance intriguingly challenges the traditional notion that fatigue invariably leads to diminished muscle function. Contrary to expectations, our study found a notable increase in muscular strength, especially in those muscle groups directly involved in the HIIT protocols. This was particularly evident in the enhanced outcomes of the horizontal jump tests, which point to a significant boost in lower body muscle power and strength. Additionally, an improvement was also noted in muscle groups not directly engaged in the HIIT exercises, as demonstrated by the increased isometric hand strength observed after the second series of HIIT. This broadening of benefits across various muscle groups underscores the comprehensive impact of HIIT, suggesting that its effects transcend the specific muscles actively engaged in the exercises. The unexpected improvement in muscular strength, despite the presence of fatigue, could be attributed to the heightened sympathetic activation that accompanies HIIT. This activation is believed to enhance the transmission of neural signals to the muscles, thereby potentially augmenting muscular performance. Such a mechanism is supported by studies suggesting that increased sympathetic activity can lead to a more efficient recruitment of muscle fibers [38]. This enhanced neural engagement may not only counteract the effects of fatigue but also facilitate a greater activation of muscle groups, including those not directly involved in the exercise regimen. This phenomenon provides a plausible explanation for the observed improvements in muscle function post-HIIT, highlighting the complex interplay between neural mechanisms and muscular adaptations induced by high-intensity exercise. The incorporation of intermittent recovery periods within the HIIT design is pivotal in facilitating sustained muscular performance, even amidst escalating fatigue.