What is this HRV thing?

A few months ago, my watch started tracking a new metric for me – HRV, or Heart Rate Variability.

At first, I didn’t pay it much mind. As you know, I’m mainly interested in my Body Battery metric, my sleep metrics, steps, and sometimes stress. These seem to have the biggest impact or correlations with my energy levels.

But then, one day, I woke up tired even though I’d had a good night’s sleep. I checked my Body Battery and it concurred – it had recorded a good night’s sleep, but a markedly reduced Body Battery. What was the deal?

Scanning through my Garmin Connect app, I noticed that my HRV metric had dropped rather dramatically during the night. It didn’t really register on my stress metric, but something with my heart rate was going on. What was that all about?

So I decided to do some more investigation. The last time I had checked, the Body Battery had mainly depended upon sleep quality, stress levels, and activity levels from the day before. Here is a screenshot of their old definition:

But when I checked again, they had updated their algorithm. Here is Garmin’s new definition for how they calculate the Body Battery:

Body Battery is a feature that uses a combination of heart rate variability, stress, and activity to estimate a user’s energy reserves throughout the day. It records and displays a number from 1-100 that represents the individual’s energy level.

https://support.garmin.com

Whoa! They don’t even mention sleep quality anymore. HRV has taken the front seat and I don’t know what it is or how to improve it. And considering how it skyrocketed to the front of the line and seems to be everywhere I turn nowadays, I have to ask myself one question:

Is HRV the new gold standard for energy metrics?

Is this why I seem to have less energy than other people even though I am getting enough sleep, eating right, and exercising? Is it genetic or something I can control? Is this my secret path to more energy? OK, I have a lot more than one question, but it is fascinating to see the science developing right before my eyes. Let’s start with the basics.

What is HRV?

Harvard’s health blog defines HRV as, “a measure of the variation in time between each heartbeat”.

Our heart rate is the number of times our hearts beat per minute. Our heart rate variability measures the change in speed of our heart beats – how quickly our hearts can speed up during stress and how quickly they can relax.

We can think of this as a measurement of how flexible our hearts are. Can they respond to stressors quickly? And can they just as quickly relax? If we get stuck in a constantly stressed state, our hearts will burn out. And if we can’t get excited when we need to, that isn’t good either. HRV is a measurement of our adaptability, essentially.

A high HRV score has been linked with greater cardiovascular fitness and resilience to stress. But when “the system is in more of a fight-or-flight mode,” as Harvard puts it, “the variation between subsequent heartbeats tends to be lower.”

What is a normal HRV score?

This is a much more contentious subject. My current average HRV score is a 31. According to this article published in Global Heart, the average HRV for a healthy male my age is 43 (+/-15). So I’m on the lower end of the spectrum there. However, this website published their users’ HRV scores and their average for my age was 56:

Does that mean I’m too stressed? Not fit enough? Drinking too much caffeine? Over-training? Not relaxing enough? So many questions!

Then, I also heard from Brian Johnson during one of his +1’s that his HRV was 79! He was born the same year I was, but my HRV is less than half of his? Well, to be honest, I feel less than half as energetic as he looks, so maybe that makes sense.

But what did Brian credit his high numbers with? He said his #1 way to help his HRV is by eating around 5 hours before bed. Also:

  • staying hydrated
  • zero tech inputs
  • evening walk, meditation, and no screens
  • Sleep tape and other things to encourage deep sleep
  • exercise (but not too much)

Brian basically does everything right, which I’m slowly trying to set up healthy habits for too, but I’m going to start my experiment with his #1: eating 5 hours before bed. This won’t make my wife happy, but she will hopefully understand.

I will try to update you here when this experiment is done!

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