The most salient result of our present study is the fact that four weeks of aerobic exercise after MI significantly increased protein expression and mRNA levels of CHI3L1 and its receptor PAR2 in the border zone of MI (Figure 4) and significantly improved post-MI ventricular function and reduced myocardial fibrosis (Figure 2). This evidence concerns the gene CHI3L1 and Myocardial fibrosis.