## 4 Discussion
### Chronic Load  
Regarding chronic load, a congested week of preseason was analyzed to observe if there were significant changes in the variables total protein, SlgA, TAC, TOS, and oxidative stress index at three time points (see Figure 2) compared to PRE levels. The findings did not show significant differences in any of the evaluated variables beyond the results shown in the acute load mentioned earlier. However, there appears to be a positive trend between the chronic load during a congested week of the precompetitive season and the decrease in total protein and SlgA levels, and a positive relationship was found between internal training loads and oxidative/antioxidant responses.  
Total protein and SlgA levels did not show significantly altered values at 48 h or 120 h, indicating that the subjects included in this study do not show a risk of contracting upper respiratory tract infections (URTIs) due to a decreased immune reaction, as shown in other studies [13, 53, 54, 55] where a significant depletion of SlgA was found with the progression of workloads supported by athletes. The findings may be due to the large interindividual variability of the variables (total protein and SlgA), as well as the small sample size. Additionally, the time of measurement of the mentioned variables appears to be a determining factor for their determination; most articles that have analyzed this variable show highly heterogeneous measurement times [20, 23, 24, 25, 27, 44, 45, 46, 47, 48, 49], making it difficult to determine the most suitable time to measure this variable, as we can find in other variables such as lactate, of which we know that its optimal measurement time is around 3-5 min after activity [56]. The values of TAC, TOS, and oxidative stress index remained unchanged (see Figure 2), indicating that the chronic load supported by elite futsal athletes during the evaluated week in the preseason showed no signs of oxidative stress. The TOS and TAC variables behaved similarly, resulting in an unchanged oxidative stress index. The loads induced on these athletes during this period were optimally assimilated at the oxidative level by all elite players, showing no signs of a high oxidative stress index.  
The present findings indicate that after a congested period of matches and training during the competitive preseason in elite futsal players, total protein and SlgA variables have proven to be sensitive in detecting physiological changes in athletes under acute load. Additionally, SlgA emerges as a more sensitive variable than total protein in distinguishing between training and matches, partly explained by the influence of sympathetic nervous system activity. This study suggests that chronic load does not appear to diminish SlgA levels. However, this does not imply that SlgA should be disregarded as a potential mechanism that could render athletes more susceptible to infection, especially during periods of overreaching or overtraining. Moreover, given the nature of team sports and their distinct demands compared to endurance exercises, the likelihood of different effects should be considered. Regarding the oxidative stress index, players did not exhibit signs of oxidative stress under acute and chronic loads, indicating optimal assimilation of the load during congested matches and training schedules.