## 3 Results  
Analyzing the results of cardiopulmonary parameters, both averaged and peak values, statistically significant differences were found between SIE\({}_{10\%}\) and SIE\({}_{7.5\%}\) in VO\({}_{2}\)mean and HR mean. Both values were lower in the interval session with a 10% load of the participant's body mass. An inverse positive trend was observed in lactate levels after performing SIE\({}_{10\%}\) (Table 2). In the first series, in the experimental condition (SIE\({}_{10\%}\)), HR mean was higher compared to SIE\({}_{7.5\%}\), respectively 174 \(\pm\) 6 vs. 168 \(\pm\) 8 (\(p\) < 0.01; ES = 0.9). Similarly, differences were observed in the second series as follows: 180 \(\pm\) 8 vs. 177 \(\pm\) 9 (\(p\) < 0.01; ES = 0.4). In both the first and second series, we observed lower RPE (\(p\) < 0.01) in the experimental condition (SIE\({}_{10\%}\)) as follows: first series 16 to 18 (\(p\) < 0.01; t = 3.6; ES = -1); second series 17 to 19 (\(p\) < 0.01; t = 6.6 ES = -1.3). In addition, the course of 5 min restitution after the second series was analyzed. Statistically significantly lower oxygen uptake (15%, \(p\) < 0.01) and heart rate (3.9%, \(p\) < 0.01) were observed in the first minute of restitution in the SIE\({}_{10\%}\) protocol compared to SIE\({}_{7.5\%}\) (Figure 2). Statistical significance was demonstrated in the higher fatigue index in the first series in SIE\({}_{10\%}\) (Table 3). The mean value of total work in the first and second series was not statistically significantly different between conditions. When comparing the relative peak power output in subsequent repetitions of the first and second series in both conditions (SIE\({}_{7.5\%}\) vs. SIE\({}_{10\%}\)), a statistically significant difference was observed in the first repetition of the first series (Figure 3). A 10.3% higher power output was obtained in the SIE\({}_{10\%}\) compared to the SIE\({}_{7.5\%}\) (\(p\) < 0.01, t = 3.8). \begin{table} \begin{tabular}{l l l l l} \hline \hline
**Values** & **SIE\({}_{7.5\%}\)** & **SIE\({}_{10\%}\)** & **t-Test** & **ES** \\ \hline VPEeak (L-min\({}^{-1}\)) & 154.6 \(\pm\) 5.3 & 154.8 \(\pm\) 9.2 & \(-\)0.03 & 0.1 \\ VPEmean (L-min\({}^{-1}\)) & 79.4 \(\pm\) 7.9 & 75.4 \(\pm\) 7.9 & 1.2 & \(-\)0.5 \\ VO\({}_{2}\)peak (mL-kg\({}^{-1}\cdot\)min\({}^{-1}\)) & 47.7 \(\pm\) 6.0 & 47.4 \(\pm\) 6.0 & 0.1 & \(-\)0.1 \\ VO\({}_{2}\)mean (mL-kg\({}^{-1}\cdot\)min\({}^{-1}\)) & 29.1 \(\pm\) 2.3 & 26.0 \(\pm\) 1.4 & 3.9 & \(-\)1.6 \\ VTpeak (L) & 3.7 \(\pm\) 0.7 & 3.4 \(\pm\) 0.3 & 1.6 & \(-\)0.6 \\ VTmean (L) & 2.5 \(\pm\) 0.4 & 2.3 \(\pm\) 0.4 & 1.6 & \(-\)0.5 \\ HRpeak (beats-min\({}^{-1}\)) & 186 \(\pm\) 6 & 188 \(\pm\) 6 & \(-\)1.6 & 0.3 \\ HRmean (beats-min\({}^{-1}\)) & 152 \(\pm\) 10 & 150 \(\pm\) 10 & 2.4 & \(-\)0.2 \\ T (\({}^{\circ}\)C) & 36.1 \(\pm\) 0.3 & 36.2 \(\pm\) 0.4 & \(-\)0.8 & 0.3 \\ La\({}^{-}\) mean (mmol\(\cdot\)L\({}^{-1}\)) & 12.6 \(\pm\) 1.0 & 13.1 \(\pm\) 2.1 & \(-\)1.3 & 1.2 \\ RPEmean (AU) & 19 \(\pm\) 1 & 17 \(\pm\) 2 \({}^{*}\) & 3.1 & \(-\)1.3 \\ \hline \hline \end{tabular}  Parameters are presented as arithmetic mean and standard deviation (\(\overline{x}\) \(\pm\) SD), peak or mean. VO\({}_{2}\)—oxygen uptake; VPE-pulmonary minute ventilation; VT—tidal volume; HR—heart rate; T——When analyzing the time to achieve PPO in each repetition, a statistically significantly shorter time of 25.5% was observed (\(p\) < 0.05, t = 2.3) during the second repetition of the second series at SIE\({}_{10\%}\) compared to SIE\({}_{7.5\%}\) (Figure 4). The time to achieve PPO was statistically significantly lower during the second repetition of series II during SIE\({}_{10\%}\). Figure 2: Course of 5 min restitution of HR (**A**); VO\({}_{2}\) (**B**); VE (**C**); and VT (**D**) after SIE with 7.5% (SIE\({}_{7.5\%}\)) and 10% (SIE\({}_{10\%}\)) load relative to body mass. * statistically significant difference (\(p\) < 0.05) in the first minute of restitution between conditions.