During and after long periods of physical exertion the muscles in the center of my chest start to ache, while at the same time I have a rapid heart beat. It feels like they are sore. Which could very well be the case. I don't believe that the pain is heart related, because I have been to my doctor about it before and he didn't believe it was. He gave me an EKG test about 3 or 4 times and every time the results were normal. I am 40 years old and generally in good health. I think the problem could probably just be common muscle strain. But I want to make sure it isn't anything more serious. Any ideas?