Swimmer Michael Phelps won a record eight Olympic gold medals in the 2008 summer games in Beijing. When he's resting, Phelps' heart rate per minute is in the low 30s - or about half of what would be considered "normal" for adults.
That's a good thing, says Thomas Lee, editor of the Harvard Heart Letter.
"Greater physical fitness leads to a slower heart rate, and a slower heart rate means less stress on your cardiovascular system," he says.
Lee writes about heart rate and longevity in the December issue of the publication.
"When you get above 100 beats per minute, you actually have to wonder, is there some kind of heart rhythm disorder that needs more immediate medical attention?"
Decongestants, asthma medicine, caffeine and other stimulates can also speed up your heart. Lee says while some drugs can slow the rate down and even give some protection for those at high risk, ongoing research underscores a familiar message: "…which is [to] control the risk factors you know about. Control your weight, exercise more and make sure you don't smoke."
Lee says it's easy enough to calculate your own resting heart beat. When you get up in the morning, check your pulse by counting the number of heart beats in 15 seconds. Multiply by four. If the rate is high - 80 or above - Lee suggests talking with your doctor.