I had my blood pressure taken today (due to an eye inflammation) and when the doctor asked how much I exercised I was expecting to hear some bad news, but apparently my resting heart rate is 53bmp, while the average is 60-90. Something around 50bmp is more commonly associated with athletes.
So get some tests done, you might turn out to be superhuman! (Or have some problem with your heart that stops it from beating at a normal rhythm?!!?!)