## 6 Results  
Out of the 94 genes that were analyzed in the present study, seven of them were significantly overexpressed in the vastus lateralis muscle samples. As shown in Table 1, they corresponded to enhancer of zeste 1 polycomb repressive complex 2 subunit (EZH1), lysine methyltransferase 2A (KMT2A), lysine methyltransferase 2D (KMT2D), lysine demethylase 4C (KDM4C), lysine demethylase 6A (KDM6A), CREB-binding protein (CREBBP), histone deacetylase 10 (HDAC10), histone deacetylase 4 (HDAC4), DNA methyltransferase 3 like (DNMT3L), and X variant histone (H2 AX). Thus, 10.6% of the 94 genes analyzed may explain the behavior of VO\({}_{2}\) in relation to skeletal muscle activity, for the target population in this study.  
The most significant biological processes associated with the overexpressed genes obtained from the constructed network included chromatin organization (FDR 9.04 \(\times\) 10\({}^{-9}\)) and histone modification (FDR 9.04 \(\times\) 10\({}^{-9}\) (Table 2), which are relevant for the function and contraction of muscles.  
The significant protein functions associated with the genes assessed, obtained from the co-expression network, were methyltransferase complex and deacetylase activity in 20 weeks of aerobic training (Figure 1).  
The PCA showed that 53% and 54% of the accumulated variance was attained within two components in the pre-training (Figure 2) and post-training samples (Figure 3), respectively.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Gene ID** & **Symbol** & **Z-Score Post** & **Z-Score Pre** & **Z-Ratio** & **\(p\)-Value*** \\ \hline
2145 & EZH1 & \(-\)0.03 & \(-\)0.19 & 2.15 & \(<\)0.00001 \\
4297 & KMT2A & \(-\)0.85 & \(-\)1.08 & 3.03 & \(<\)0.00001 \\
8085 & KMT2D & \(-\)0.98 & \(-\)1.15 & 2.30 & \(<\)0.00001 \\
23081 & KDM4C & 0.53 & 0.33 & 2.69 & \(<\)0.00001 \\
7403 & KDM6A & \(-\)0.84 & \(-\)1.11 & 3.64 & \(<\)0.00001 \\
1387 & CREBBP & \(-\)0.09 & \(-\)0.24 & 2.09 & \(<\)0.00001 \\
83933 & HDAC10 & 0.15 & \(-\)0.00 & 2.00 & \(<\)0.00001 \\
9759 & HDAC4 & \(-\)0.12 & \(-\)0.30 & 2.38 & \(<\)0.00001 \\
29947 & DNMT3L & \(-\)0.78 & \(-\)0.95 & 2.35 & \(<\)0.00001 \\
3014 & H2 AFX & 0.33 & 0.12 & 2.83 & \(<\)0.00001 \\ \hline \end{tabular}
*Statistically significant \(p\)-value.  
\end{table}
Table 1: Description and expression data of overexpressed genes associated with chromatin modifications included in the present study.  
\begin{table}
\begin{tabular}{c c c} \hline
**GO\_ID** & **Description** & **Gene Count** & **FDR** \\ \hline
6325 & Chromatin organization & 9 & \(9.04\times 10^{-9}\) \\
16570 & Histone modification & 8 & \(9.04\times 10^{-9}\) \\
18205 & Peptidyl-lysine modification & 7 & \(1.07\times 10^{-7}\) \\
16571 & Histone methylation & 5 & \(2.04\times 10^{-6}\) \\
43414 & Macromolecule methylation & 6 & \(2.32\times 10^{-6}\) \\
6996 & Organelle organization & 10 & \(4.69\times 10^{-5}\) \\
40029 & Regulation of gene expression, epigenetic & 5 & \(4.69\times 10^{-5}\) \\
34968 & Histone lysine methylation & 4 & \(5.13\times 10^{-5}\) \\
10604 & Positive regulation of macromolecule metabolic process & 10 & \(5.25\times 10^{-5}\) \\
45934 & Negative regulation of nucleobase-containing compound metabolic process & 8 & \(6.02\times 10^{-5}\) \\
51172 & Negative regulation of nitrogen compound metabolic process & 9 & \(6.51\times 10^{-5}\) \\ \hline \end{tabular}
\end{table}
Table 2: Description of outstanding biological processes obtained from the network constructed with the genes significantly associated with chromatin modifications in vastus lateralis muscle.  
Figure 1: Co-expression interaction network obtained with the 10 significantly overexpressed genes associated with muscle function evaluated.  
Figure 2: Principal component analysis of pre-training samples with the overexpressed genes found in this study shown as green dots.