## 3 Results
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Population Group** & **OR (Lower CI–Upper CI)** & **Q1/Q2** & **Q1/Q3** & **Q1/Q4** & **Q2/Q3** & **Q2/Q4** \\ \hline Total Federated & 0.993 (0.96–1.03) & 1.069 * & 1.137 * & 1.077 * & 1.146 * & 1.063 * \\  & (1.03–1.11) & (1.10–1.18) & (1.04–1.11) & (1.11–1.19) & (1.03–1.10) \\ TF-F & 0.964 (0.91–1.02) & 1.108 * & 1.073 * & 1.150 * & 1.113 * & 0.968 \\  & (1.05–1.17) & (1.01–1.14) & (1.09–1.22) & (1.05–1.18) & (0.91–1.03) \\ TF-M & 1.009 (0.97–1.05) & 1.049 * & 1.175 * & 1.039 * & 1.164 * & 1.120 * \\  & (1.01–1.09) & (1.13–1.23) & (1.00–1.08) & (1.12–1.22) & (1.07–1.17) \\ Youths & 0.971 (0.91–1.04) & 1.246 * & 1.261 * & 1.284 * & 1.299 * & 1.012 \\  & (1.16–1.33) & (1.18–1.35) & (1.20–1.37) & (1.21–1.39) & (0.94–1.09) \\ F-Y & 1.021 (0.92–1.13) & 1.388 * & 1.198 * & 1.360 * & 1.174 * & 0.863 ** \\  & (1.25–1.54) & (1.08–1.33) & (1.22–1.51) & (1.06–1.30) & (0.77–0.96) \\ M-Y & 0.937 (0.86–1.02) & 1.158 * & 1.309 * & 1.236 * & 1.397 * & 1.131 * \\  & (1.06–1.26) & (1.20–1.43) & (1.13–1.35) & (1.28–1.53) & (1.03–1.24) \\ Elite & 1.059 (0.90–1.25) & 1.543 * & 1.136 & 1.457 * & 1.073 & 0.737 ** \\  & (1.30–1.84) & (0.96–1.34) & (1.22–1.74) & (0.91–1.27) & (0.62–0.88) \\ F-E & 0.731 ** (0.55–0.97) & 0.947 & 0.881 & 1.296 & 1.205 & 0.929 \\  & (0.71–1.26) & (0.66–1.17) & (0.98–1.71) & (0.92–1.58) & (0.70–1.23) \\ M-E & 1.301 * (1.06–1.60) & 2.054 * & 1.301 * & 1.578 * & 1.000 & 0.634 ** \\  & (1.65–2.56) & (1.06–1.60) & (1.26–1.98) & (0.81–1.24) & (0.50–0.80) \\ \hline \hline \end{tabular} Note. (*) Positive statistical significance (95% C1) = 1; (**) Negative statistical significance (95% C1 < 1). Total Federated includes all categories of the SQL, for both female (TF-F) and male (TF-M) athletes. The youths subgroup encompasses the F-Y categories (F-12, F-14, F-16, F-18, F-20), and M-Y categories (M-12, M-14, M-16, M-18, M-20). Additionally, it includes the elite subgroup, consisting of the elite female (F-E) and male (M-E) categories. Q1 = born in the first quarter of the year (January–March); Q2 = born in the second quarter of the year (April–June); Q3 = born in the third quarter of the year (July–September); Q4 = born in the fourth quarter of the year (October–December).  
\end{table} 
Table 6: Odds ratios (OR) and confidence intervals (95%) for comparisons between birth quartiles in the different studied population groups. Figure 3: Bar chart representing the birth date distribution by semester (S1 and S2) for male athletes according to their age group. (*) Statistically significant differences compared to athletes born in S1 (January–June), \(p\) < 0.05. In green, above each blue column (S1), the Cramer’s V value, indicative of the effect size, is shown for the S1/S2 relationship. In general, men (TF-M, M-E) show stronger associations between quartiles, especially between the Q1/Q4 and Q1/Q3 pairs, compared to women. In the Total Federated population (TF), significant associations are observed in all comparisons except Q1/Q2. Similarly, in the subgroup of young athletes (Youths), significant differences are observed between all compared pairs except Q1/Q2 and Q3/Q4. Notably, differences between Q1/Q2 only exist in the F-E group (inverse relationship) and M-E group. Meanwhile, Table 7 presents the ORs and their 95% CIs for the comparisons between birth quartiles in the different age groups evaluated. As with the population groups, associations between birth quartiles and participation in various competitive categories were examined using the Z-test, and the results are consistent with the interpretations of the ORs' 95% confidence intervals. Therefore, comparisons where the OR values reflect significant positive (95% CI > 1) or negative (95% CI < 1) associations are marked with an asterisk (*) for positive statistical significance (95% CI > 1) and a double asterisk (**) for those with a significant but less than one OR.