qRT-PCR analysis demonstrated that the mRNA expression levels of Col1a1, Col3a1, TGF-β1, Smad2, Smad3, and Smad4 were considerably upregulated in DCM mice relative to controls, whereas all three exercise modalities downregulated their expression, and HIIT exerted the most pronounced inhibitory effect (Figure 4D–I). This evidence concerns the gene COL3A1 and familial dilated cardiomyopathy.