Your heart doesn’t beat in the exact same rhythm.

(it’s hard to notice because it’s a matter of milliseconds)

But it actually varies.

So if your heart rate is 60 beats per minute, it doesn’t actually beat once per second. Could be 0.96, 1.03, 1.05, 0.99…

The average difference between each beat is known as your heart rate variability (HRV).

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It’s dictated by our nervous system.

The heart has a little dude on each shoulder.

1. The parasympathetic system tells the heart rate to slow down
2. The sympathetic system tells it to speed up

And it’s this tug of war that creates the variation.

See if we’re in balance the heart hears both systems. It reacts to each. It’s responsive. It’s healthy.

If we’re out of balance, usually our sympathetic system is dominant. We might be stressed, fatigued, sick.

And the parasympathetic gets drowned out. So the heart mostly hears the sympathetic “speed up” signal. Which means there’s less variance in our heart rate.

So a high HRV is what we’re after 👍

It’s a really good indicator of stress and general health.

So if your wearable tracks HRV have a look at how it’s trending.

If you wanna see how you sit for your age, here's data from Whoop (keep in mind the people who use Whoop will tend to be fitter and healthier than average – so a good yardstick for the everyday athlete):

But it's highly individual. Genetics play a big part in your HRV. So I’d be more interested in tracking your trends than comparing you to other people.

If it’s trending down over a couple days, it might be a sign you need to back off training a little, hone in on sleep and chill out.

And zooming out to a 3-month view can tell you if you’re training and lifestyle are helping move you in the right direction.

How to improve HRV?

Nail the basics – eat, sleep and train well.

Get the recovery matching balance right.

Start pulling out the physiological sigh more often.

Watch it fly.