A rookie who hasn't been to the gym for a long time finished practicing his chest muscles yesterday. Today, his left chest is obviously more painful than his right chest, and he is worried that he will become a different chest muscle. The main reason is that your left chest muscles are looser than your right chest. For example, if your right hand is stronger than your left hand, then the result of your exercise is very good. If you practice regularly, your chest muscles will develop. Unless you are left-handed, of course, your left side is overexertion. I hope it helps you. Thank you.