MMP9 and Myocardial fibrosis: A study has reported that moderate aerobic exercise significantly downregulated the expression of MMP2 and MMP9 proteins in myocardial tissue after acute myocardial infarction in rats, while promoting the expression of their inhibitor TIMP2, effectively improving the degree of myocardial fibrosis and alleviating ventricular remodeling after myocardial infarction (85).