## 2 Materials and Methods
### Statistics Analysis  
Statistical analysis was performed with OriginPro version 2019b software. (OriginLab. Northampton USA). The significant \(p\)-value was set at \(p\) = 0.05. Means and standard deviations for each of the variables were used to describe the data collected. Outliers were eliminated using the range between the 10 th and 90 th percentiles for each of the primary variables (height, weight, body fat percentage [BF%] and muscle mass). Based on the primary variables without outliers, the percentages of change between months were calculated (Formulas (1) and (2)). Subsequently, the means of the two percentage changes (MPC) produced in a trimester were calculated, and a variable called trimestral percentage change (TC) was obtained (Formula (3), which was subsequently used in the statistical analyses. 1 st monthly percentual change (MPC1) (%) = (Month 2 value-Month 1 value)/(Month 1 value) \(\times\) 100 (1)  
2 nd monthly percentual change (MPC2) (%) = (Month 3 value-Month 2 value)/(Month 2 value) \(\times\) 100 (2)  
\[\text{ Trimestral percentual change (TC) (\%)}=(\text{MPC1 + MPC2})/2 \tag{3}\]  
Once this was done different Two-Way Repeated Measures ANOVA were performed, including the raw variables (height, weight, body fat percentage and muscle mass) or the TC of each raw variable (height-TC, weight-TC, body fat percentage-TC and muscle mass-TC) as dependent variables. Age category (13, 14, 15, 16, 17 and 18 years) and trimester (1 st, 2 nd and 3 rd), were the between and within- independent variables. Two-Way Repeated Measures ANOVA analysis was also performed including as dependent variable the averaged trimestral change per variable in percentage and as independent variables the age category variable (between groups: 13, 14, 15, 16, 17 and \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline Time & Monday & Tuesday & Wednesday & Thursday & Friday & Saturday/Sunday \\ \hline
7:45–8:45 & Rest & Rest & \begin{tabular}{c} Strength \\ Training \\ \end{tabular} & Rest & \
\begin{tabular}{c} Strength \\ Training \\ \end{tabular} & Rest &
\begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} & \multirow{2}{*}{Match} \\
16:45–18:00 & \begin{tabular}{c} Recovery \\ Training \\ \end{tabular} & \begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} & Rest & \begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} & \multirow{2}{*}{Rest} & \multirow{2}{*}{\
\begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} } \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Typical week for group U13-U14-U15. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline Time & Monday & Tuesday & Wednesday & Thursday & Friday & Saturday/Sunday \\ \hline
7:45–8:45 & Rest & \begin{tabular}{c} Strength \\ Training \\ \end{tabular} & Rest & \
\begin{tabular}{c} Strength \\ Training \\ \end{tabular} &
\begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} & \multirow{2}{*}{Match} \\
16:45–18:00 & \begin{tabular}{c} Recovery \\ Training \\ \end{tabular} & \begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} & Rest & \begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} & \multirow{2}{*}{Rest} & \multirow{2}{*}{\
\begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} Technical-Tactical \\ Training \\ \end{tabular} } \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Typical week for group U16-U17-U18. 18 years) and the anthropometric trimestral change variables (withing groups: height-TC, weight-TC, BF%-TC and MM-TC). For all Two-ways ANOVAs, [PERSON]'s test of sphericity was performed. If the assumption of sphericity was not met (\(p\) < 0.05) and if the Epsilon value was greater than 0.75, the Huynh-Feldt correction was applied. If the normality assumption was not met and the Epsilon value was less than 0.75, the Greenhouse-Heisser correction was applied.