As A. O’Connor’s recent New York Times article states, a normal adult resting heart rate is considered to be anywhere from 60-100 beats per minute (BPM). But like most things related to the human body, there are plenty of notable nuances and exceptions. O’Connor’s article does a nice job covering the medical considerations related to higher heart rates in the upper end of that “normal” range. But what about “abnormally” low heart rates?
The main concern about a low resting heart rate (assuming an otherwise normal heartbeat) is that your heart isn’t pumping out enough blood to your body, particularly to your brain. And the main signs that your brain is not getting an adequate amount of blood are feelings of faintness, light-headness or dizziness. So if your resting heart rate is less than 60 but you don’t have any of these symptoms, then the likelihood of your low heart rate signifying a problem is very low. Any signs of an abnormal heart rhythm however (e.g. sudden periods of heart racing, skipped beats, etc), absolutely need to be evaluated by a physician regardless of heart rate.
As many athletes are aware, the more fit you are, the lower your resting HR tends to be. Under those circumstances, the heart muscle has become so strong and efficient that it is able to pump out more blood with each beat, thereby satisfying your body’s needs with fewer beats.