## 4 Discussion
### Acute Load  
Regarding the relative changes in SlgA in acute load, previous studies involving elite athletes within their regular training regimens or competitive settings have shown that intense endurance exercise typically leads to reduced levels of SlgA post-exercise [43]. This consensus is supported by numerous studies illustrating declines in SlgA levels following intense physical exertion [20; 23; 24; 25; 44; 45]. However, the present study did not find evidence to support the hypothesis that a congested period of matches and training sessions during the futsal preseason would transiently suppress mucosal immune function in elite players, as assessed by SlgA levels. Notably, increases in SlgA, as observed in the players (see Figure 1), have been similarly reported in prior investigations [27; 46; 47; 48]. These discrepancies in the scientific literature may be attributed to the variability in the SlgA measurement employed in the studies to elucidate the findings. The ratio of SlgA to total protein (SlgA/Pro ratio) has been investigated and discussed in previous exercise immunology research papers. [PERSON] et al. [49] reported a higher percentage of SlgA depletion when this variable was expressed relative to the concentration of total proteins. However, it has been suggested that utilizing the ratio of SlgA to total protein concentration can lead to misinterpretation due to the fact that the total protein content of saliva is considerably more variable due to the high concentrations of enzymes such as amylase, which are induced by flow rate stimulation. It may be more appropriate to express salivary IgA concentration as a ratio to albumin, as albumin is less influenced by flow rate and is not actively secreted across the epithelial membrane [46; 50].  
Regarding total protein, the results of the present study also show that there was a significant increase in total protein from PRE (1.49 \(\pm\) 0.79 mg/mL\({}^{-1}\)) to POST (2.25 \(\pm\) 1.40 mg/mL\({}^{-1}\)) training and PRE (1.31 \(\pm\) 0.77 mg/mL\({}^{-1}\)) to POST (1.81 \(\pm\) 1.22 mg/mL\({}^{-1}\)) match. These findings support the results found in other studies [46], which showed increases in total protein concentrations (0.48 \(\pm\) 0.10 mg/mL\({}^{-1}\) to 1.80 \(\pm\) 0.38 mg/mL\({}^{-1}\)). The role of total protein in immunological studies and the changes in protein levels under different physiological conditions are still poorly understood. These limitations are extensive for most of the salivary protein functions [51]. In addition, between matches and training sessions, during acute loads, total protein seems to be a less sensitive variable for determining the acute effect on elite futsal players compared to SlgA; these changes appear to be largely due to stimulation of amylase secretion by increased sympathetic nervous activity, which appears to have a greater effect on SlgA levels [52].  
Concerning the relative changes in TOS, TAC, and oxidative stress index under acute loading conditions, the present study did not observe statistically significant differences (\(p>0.05\)) in all variables, except for TAC. This discrepancy could be attributed to a intra-subject coefficient of variation (33.45%). Oxidative responses to workload are inherent to the body's physiological processes. However, to ascertain the body's oxidative load tolerance, it is imperative to scrutinize its antioxidant response. Therefore, the TOS/TACratio serves as an indicator of the oxidative stress index. Furthermore, as demonstrated in Table 2, match-related loads elicit a significant increase in both TOS and TAC variables (\(p\)-value \(<\) 0.02 and \(p\)-value \(<\) 0.01, respectively) compared to training sessions. Nevertheless, no distinctions are evident in the oxidative stress index, suggesting that the antioxidant defense mechanism adequately counteracts the oxidative demands. These findings imply that subjects in this study did not exhibit oxidative stress in response to acute loads during the congested match and training schedule.