## 4 Discussion  
The main objective of this study is to examine T and C concentration levels over a 16-week competitive period to gain a more comprehensive understanding of sporting performance in elite female volleyball players. The main results describe that serum total T concentrations were higher (0.7 ng/mL vs. 0.35 ng/mL), twice the ranges recorded in  
Figure 5: Correlations established between T and physical fitness tests at T1. Figure 6: Correlations established between T and C and physical fitness tests at T2. previous studies in female volleyball players [1] at both time points, although the values obtained are within the theoretically established ranges for serum total T of 0.3-0.9 ng/mL for women. The results also show that C levels were on average 4.7% (19.1 ug/dL vs. 18.2 ug/dL) higher at T1 and 1.57% (18.5 ug/dL vs. 18.2 ug/dL) according to these studies, ranges that are also within the theoretically established levels for basal C in women of 6-30 ug/dL. Of note, the hormone levels observed in this study were higher than those commonly used as a reference in clinical practice, which are derived from a \"reference\" population of healthy women [2]. Consistent results from different statistical methods suggest that young female athletes differ constitutively from the general female population in terms of their hormone levels [96]. Since the T concentration between moments has improved (2.945%) in the body of the participants, without being a significant change, this will tend to develop muscle mass more easily and therefore athletic performance will increase, as observed in some of the CMJ (3.0% \(\pm\) 2.2%; \(p\) = 0.002) and ABK (2.2% \(\pm\) 3.1%; \(p\) = 0.028) jumps, with significant changes between moments. Consequently, and knowing that muscles are the most energy-consuming tissue, participants will increase their energy expenditure the more physical activity they do, while developing their muscle mass according to their situation [3]. In the case of T, the more T that is secreted (within established theoretical levels) and the more physical exercise that is performed, the more muscle mass and strength will increase. Furthermore, as this hormone speeds up metabolism, it will help to lose body fat, while increasing muscle mass [3]. This will help participants to increase their level of jumping, as we have seen. We can see that, as mentioned above, participants have T concentration levels that are within the established theoretical parameters at both time points, with a slight percentage increase (2.945%) between time points. This indicates that, although not by much, the work performed between time points has been adequate. The correlations between T and the agility test at T1 (high) showed the expected pattern of correspondence, with a considerable magnitude of change, indicating a high causal probability of the changes produced not being influenced by chance and that being negative indicates that the level of T influences this type of test inversely proportional to the reduction in test times. The Illinois agility test is considered a standard agility test [8] due to its high validation and reproducibility [9,10]. It is used to assess speed and agility abilities, including reaction time, acceleration, deceleration and change of direction [11], and it is used to quantify changes in directional ability [12]. The intraclass correlation coefficient and standard error of measurement values for the test are 0.96 (95% CI, 0.85-0.98) and 0.19 s, respectively. The validity of the COD IAGT has been assessed with the t-test, yielding a correlation coefficient of r = 0.31 (95% CI, 0.24-0.39) and a significant \(p\)-value \(<\) 0.05 [9]. These findings suggest that the COD IAGT is a reliable and valid test for assessing agility. The measurement scales showed high significant correlations at T1 between T and the ABK jump (high), a significant disturbance suggesting a minimal probability of chance, because it is an action that requires explosive strength and coordination.