Yes it is true, you can hurt your pectoral muscles. At your age i would say it's probably not "heart" related. If your very worried i would ask the doctor for a stress test. A stress test determines ischmia and how much your heart works when exercising. it's a great test to tell a doc if you have any heart disease. Another test is an echo cardiogram which looks at the chambers of your heart to see the blood flow of the valves, to check for stenosis. I wouldn't be worried, if your doc thinks your fine and you have no positive family history. I would do an stress test if: -you have sharp stabbing pains with exersion (with activity) - have shortness of breath -have numbness, pain shooting down your left arm, shoulders or jaw -weakness, increasingly tired If not it's probably just a pulled muscle (which has happened to me when i work out my chest). Give it a few days and see what happens but if you have many of the symptoms i described go back to your doc and explain to him again!