## 3 Results
### Effects of Fatigue  
In the pre-intervention moment, no significant time \(\times\) group effects (F = 2.453; \(p=0.108\)) were found in the isometric force production during the fatigue protocol. In addition, no differences were found between the NAC and control groups in any set of isometric contractions (\(p=0.467\); 95% confidence interval (CI) of the mean difference (MD) = \(-62.17\) to 29.50 N\(\cdot\)m), although a significant decrease in force production compared to basal level (time effect) was described for both groups (F = 53.962; \(p<0.001\)). The force production of the control group decreased 34.1 \(\pm\) 10.7% at the end of the fatigue protocol and a decrease of 38.1 \(\pm\) 14.1% was observed in the NAC group. After the supplementation intervention, there was no significant time \(\times\) group effect (F = 2.1; \(p=0.151\)). In addition, no differences between the NAC and control groups were found in any set of isometric contractions (\(p=0.467\); 95% CI of MD = \(-62.17\) to 29.50 N\(\cdot\)m), although a significant decrease in the force production compared to the basal level (i.e., time effect) was described for both groups  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & **PRE (N-m)** & **POST (N\(\cdot\)m)** & **POST-24 h (N\(\cdot\)m)** & **F** & \(p\)**-Value** & **pp\({}^{2}\)** \\ \hline Pre-supplementation intervention & & & & & & \\ NAC & 61.03 \(\pm\) 16.87 & 28.96 \(\pm\) 14.24 * & 57.54 \(\pm\) 24.82 & & & \\ CONTROL & 56.88 \(\pm\) 24.82 & 37.35 \(\pm\) 14.95 * & 62.68 \(\pm\) 17.37 & Group Effect & 0.110 & 0.745 & 0.006 \\ Post-supplementation intervention & & & & Time Effect & 28.391 & \(<\)0.001 & 0.916 \\ NAC & 67.85 \(\pm\) 23.26 & 42.17 \(\pm\) 19.32 * & 73.69 \(\pm\) 24.39 & Time \(\times\) Group & 0.955 & 0.479 & 0.269 \\ CONTROL & 65.86 \(\pm\) 12.83 & 46.59 \(\pm\) 13.85 * & 69.01 \(\pm\) 15.22 & & & \\ \hline \end{tabular}
\end{table}
Table 1: Maximal voluntary contraction evolution (mean \(\pm\) standard deviation).  
(F = 24.6; \(p\) < 0.001). The force production of the control group decreased 26.9 \(\pm\) 10.3% at the end of the fatigue protocol and a decrease of 32.1 \(\pm\) 16.6% was observed in the NAC group. The decrease in the isometric force production was the same for both groups, the control group and NAC group, at the pre-intervention moment (\(p\) > 0.054) and post-intervention moment (\(p\) > 0.396). Finally, after the supplementation intervention, the control group reached a maximum decrease in the isometric force production at set 4 (no differences were found in force production from set 4 to the end of the fatigue protocol (\(p\) = 0.167), but the NAC group reached the maximum decrease in the isometric force production from set 5 to the end of the fatigue protocol (\(p\) = 0.095). The results of the isometric force production during the fatigue protocol are shown in Figure 2.  
In the intra-group comparison of strength loss (all comparisons were made against the first set of the fatigue protocol) between pre- and post-intervention; in the control group, the strength loss was significantly lower at the post-intervention moment from set 5 (\(p\) < 0.017). In the NAC group, the strength loss at the post-intervention moment was lower compared to the pre-intervention moment from set 4 (\(p\) < 0.045) (Figure 3).  
Figure 2: Isometric force production during the fatigue protocol (mean \(\pm\) standard error). * Significant differences compared to set 1 at the pre-intervention moment; \(\uparrow\) significant differences compared to set 1 at the post-intervention moment; \(\uparrow\) significant differences compared to set 7 at the pre-intervention moment; \(\uparrow\) significant differences compared to set 7 at the post-intervention moment; significance criteria: \(p\) < 0.05.