HRV is one of the most useful numbers in fitness — and one of the most misunderstood. Here's what heart rate variability actually is, in plain language, and how to use it without obsessing over it.
What HRV actually measures
Your heart doesn't beat like a metronome. Even at a steady 60 beats per minute, the gap between beats varies slightly — maybe 0.9 seconds, then 1.1, then 1.0. HRV is the variation in those gaps. It's measured in milliseconds, usually overnight.
Counter-intuitively, more variation is better. High, stable HRV means your nervous system is relaxed and adaptable — your "rest and recover" mode is working well. Low HRV means your body is under stress, whether from hard training, poor sleep, illness or life.
What's a "good" HRV?
There's no universal good number. HRV varies massively between people based on age, genetics and fitness — anything from the 20s to over 100ms can be normal. Comparing your HRV to someone else's is meaningless. What matters is your trend against your own baseline. That's why a recovery tracker learns your personal baseline over a couple of weeks.
How to read the trend
Forget single days — one low reading after a late night or a glass of wine means nothing. Watch the 7-day trend:
- Stable or rising → you're adapting well; train as planned.
- Sustained drop (with a higher resting heart rate) → you're under-recovered; ease off before you dig a hole.
This is the early-warning system that helps you avoid overtraining and illness, often a day or two before you'd feel it.
What lowers your HRV
Common culprits: hard or unusually long workouts, poor or short sleep, alcohol, late caffeine, stress and dehydration. Spotting which ones tank your HRV is one of the most useful things tracking can teach you.
How to improve it over time
You don't chase HRV directly — you build the habits that raise it: consistent sleep, sensible training load, easy days that stay easy, hydration and stress management. Do those well and your baseline drifts up over months.
HRV isn't a score to win. It's a daily question: is my body ready to push, or to recover?
Used as a trend, HRV turns guesswork into informed decisions. Pair it with resting heart rate and sleep for the full recovery picture.