Effects of Continuous and Interval Aerobic Training on the Expression of TGF-β and Type I and III Collagen Genes (Fibrotic Markers) in the Myocardium of Rats with Myocardial Infarction

Myocardial infarction (MI) often leads to myocardial fibrosis due to excess type I and III collagen and TGF-β pathway activation, impairing heart function. This study aimed to investigate the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) on the expression of TGF-β, type I and III collagen genes in a rat model of myocardial infarction, to explore non-invasive strategies for reducing cardiac fibrosis. In this laboratory trial, 40 male Wistar rats were divided into four groups: healthy control (Ct), myocardial infarction without training (MI), MI with moderate-intensity continuous training (MIMCT), and MI with high-intensity interval training (MIHIIT). Myocardial infarction was induced by ligation of the coronary artery. Training protocols were performed for 8 weeks (5 days/week). MICT was conducted at 60%-75% VO2max for 45 minutes per session. HIIT consisted of seven sets of high- and low-intensity intervals: 4 minutes at 80%-90% VO2max and 3 minutes at 60% VO2max. Gene expression was measured using Real-Time PCR. Data were analyzed using SPSS, with two-way ANOVA for main effects, Tukey post hoc for pairwise comparisons, and independent t-tests to compare training groups (p < 0.05). TGF-β expression increased significantly in the MI group compared to Ct (P < 0.001), but decreased significantly in both training groups (MIHIIT: 50%; MIMCT: 30%; P < 0.001). The difference between MIHIIT and MIMCT was significant (P = 0.012). Expression of type I collagen (MIHIIT: 40%; MIMCT: 37%) and type III collagen (MIHIIT: 44%; MIMCT: 40%) also decreased, but differences between training types were not significant (P > 0.05). Aerobic training, especially HIIT, significantly reduces TGF-β expression and may attenuate cardiac fibrosis and heart failure risk. HIIT is recommended as part of cardiac rehabilitation for MI patients.