What is a athlete's heart?

There is reallyno medical medication that can treat the person that goes threw this. the only way to heal the person if my detrainig the heart muscle. since the heart is a muscle it grows when you exercise and since it is a muscle it could decrease in size. You can detraine the heart by not running or exelirating you heart beat as it usually does. That means that the heart would detraine it self and the Myocardium which is the muscle layer of the heart would decrease in size.