Doesn't it though?As we grow older, the heart rate usually slows down.And since it is a muscle, it shows that working out can improve heart rate and other vascu

Doesn't it though?As we grow older, the heart rate usually slows down.And since it is a muscle, it shows that working out can improve heart rate and other vascular conditions. "Tired" not as in the other muscles, but you can't function at 100% for long period of times.