## 3 Results
### Load  
Table 3 presents the results in terms of the variables in absolute values obtained by GPS in the U10 and U12 categories for MD-4, MD-2, and MD in the different game positions (DFs, MFs, and FWs). The U10 results with respect to MD-4, MD-2, and MD showed that MD had significantly higher values than MD-2 and MD-4 in TD, distance Z5, and distance Z6 for MFs and higher values than MD-4 in HI acceleration for MFs (\(p\) < 0.05; ES = 0.72 to 1.57). The U10 results in relation to the playing positions (DFs, MFs, and FWs) showed that the MFs presented significantly higher values than DFs and FWs in TD, distance Z5, distance Z6, and HI acceleration in MD, higher values than FWs in distance Z6 in MD-2, and higher values than FWs in ACCMAX in MD (\(p\) < 0.05; ES = 1.05 to 2.00). FWs showed significantly lower values than DFs and MFs in VMaxACC in MD-4 (\(p\) < 0.05; ES = 0.25 to 0.79).  
On the other hand, the U12 results with respect to MD-4, MD-2, and MD were as follows. MD showed significantly higher values than MD-4 in TD for MFs, higher values than MD-2 and MD-4 in distance Z5 for MFs, and higher values than MD-2 in VMaxACC for FWs (\(p\) < 0.05; ES = 1.05 to 2.39). In addition, MD-4 showed significantly higher values than MD-2 in IACC and TDACC for DFs (\(p\) < 0.05; ES = 1.08 to 1.17). The U12 results in relation to the playing positions (DFs, MFs, and FWs) showed that FWs had significantly higher values than DFs in IACC in MD (ES = 1.71; \(p\) < 0.05).  
Figure 1 shows the results in terms of the variables in relative values obtained by GPS for MD in the U10 and U12 categories for the different game positions (DFs, MFs, and FWs). In the relative results in relation to the game positions (DFs, MFs, and FWs), in the U10 category, MFs showed a significantly lower percentage of TD than DFs and FWs (\(p\) < 0.05; ES = 0.76 to 0.83). DFs showed a significantly higher percentage in distance Z5 than MFs (\(p\) < 0.05; ES = 0.97). No significant difference was obtained in the U12 category or between the two age categories.  
\begin{table}
\begin{tabular}{l c c c c c c c c} \hline  & \multicolumn{3}{c}{**U10**} & \multicolumn{3}{c}{**U12**} \\ \hline  & \multicolumn{2}{c}{**FG**} & \multicolumn{2}{c}{**CG**} & \multicolumn{2}{c}{**FG**} & \multicolumn{2}{c}{**CG**} \\ \hline  & **Pre** & **Post** & **Pre** & **Post** & **Pre** & **Post** & **Pre** & **Post** \\ \hline CMJ (cm) & 19.4 \(\pm\) 4.0 & 18.9 \(\pm\) 4.1 & 16.9 \(\pm\) 3.6 & 16.6 \(\pm\) 3.7 & 24.1 \(\pm\) 4.8 & 24.9 \(\pm\) 5.1 & 17.7 \(\pm\) 4.4 \# & 16.4 \(\pm\) 3.8 \# \\ Strength (kg) & 14.4 \(\pm\) 3.1 & 15.8 \(\pm\) 3.2 & 13.2 \(\pm\) 3.5 & 13.0 \(\pm\) 3.4 & 19.8 \(\pm\) 3.9 & 19.8 \(\pm\) 4.8 & 17.3 \(\pm\) 5.1 & 17.7 \(\pm\) 4.8 \\ VO\({}_{2}\) max & 49.4 \(\pm\) 3.5 & 52.9 \(\pm\) 3.4 \(\ast\) & 47.2 \(\pm\) 4.0 \# & 46.4 \(\pm\) 3.9 \# & 49.0 \(\pm\) 3.5 & 51.2 \(\pm\) 3.2 \(\ast\) & 42.2 \(\pm\) 3.9 \# & 42.5 \(\pm\) 4.4 \# \\ \hline  & \multicolumn{3}{c}{\#: different between control and football; \(\ast\): different between pre and post; Abbreviation: data are presented as mean \(\pm\) SD; \(\ast\): different (\(p\) < 0.05) from pre; \#: different (\(p\) < 0.05) from CG; CMJ: countermovement jump; VO\({}_{2}\) max: maximum oxygen uptake.} \\ \end{tabular}
\end{table}
Table 2: Physical condition before (pre) and after (post) a 12-week intervention with two days of training football plus one match per week in young U10 and U12 players (FG) and without football training in young controls (CG).