What Heart Rate Variability (HRV) Reveals About Your Nervous System

Heart rate variability is exactly what it sounds like. It is the variation in your heart rate. Let me use an example. Let's say your resting heart rate is 60 beats per minute. You would then assume that since there's 60 seconds in one minute, that your heart is then beating in this example every second on the second, and then if you sped your heart rate up to 60, 70 or 80 or 90 or 100 beats per minute, you would simply shorten the time between each heartbeat, but that heartbeat would be the same. It'd be one second or half a second, or three quarters of a second, or whatever the case is. Well, in that particular case, there's no variation in your heart rate. That's not actually what happens. If your heart rate is 60 beats per minute, what's going to happen naturally is maybe it beats at 1. 1 second, and then the next beat comes at 1. 2 seconds later, and the next beat after that comes 0. 9 seconds later, and then it comes at 0. 8, and then it goes to 1. 3. And so there's variations. At the end of the 60 seconds, you'll still have done 60 beats, but it won't be a metronome. It doesn't happen every second on the second. How variable that is, is the marker we're talking about. It's a little bit counterintuitive, but the more variation, the more parasympathetic you are, so the more variation in your heart rate, the more down-regulated. If it becomes like a metronome, every second on the second, it's dialed in, that means you're in sympathetic drive. Now, as I said, parasympathetic and sympathetic aren't on/off switches. They toggle back and forth. So HRV is just telling us kind of where at on that entire spectrum we are. Generally on average here, we want to spend more time in parasympathetic, meaning a higher HRV.