Your heart does not beat like a metronome. Even at complete rest the gaps between beats differ a little: now shorter, now longer. That barely noticeable spread is called heart rate variability, or HRV for short.

It sounds odd, but unevenness here is a good thing. The more freely your pulse “breathes”, the calmer and better rested your body is.

Why the spread is about recovery

Two forces argue inside you all the time. One accelerates — keeps you sharp, ready for tasks and load. The other brakes — calms, repairs, restores.

When the second force takes over, the heart allows itself that spread — and HRV rises. When you are drained, short on sleep or your body is fighting a cold, everything tightens, the beats come more evenly, and HRV falls.

That is why it is the main recovery signal. Not “am I tired in words”, but how the body actually answers.

Why the tri band looks at it during the night

By day the numbers jump from everything: coffee, stairs, a conversation, being in a rush. At night you lie still, and the body shows itself honestly — without interference.

While you sleep, the tri band quietly reads your pulse and its spread with the optical sensor on your wrist. By morning the app shows you a calm picture: how the night went and what shape you are in.

One more thing that matters: everyone has their own normal. One person's HRV is usually higher, another's lower — and that says nothing about who is healthier. Comparing yourself with your neighbour is pointless. Look only at your usual level.

And look at the trend, not at one night. A single low night is just a night. Several in a row heading down is a reason to ease off and let yourself rest.

What raises your HRV

The good news: you can influence it, and almost all of it is free.

  • Sleep. The strongest lever. Go to bed earlier and at a similar time — the body likes a routine.
  • Calm. Slow breathing, a walk, quiet before bed. Less fuss in the evening, more spread at night.
  • Less alcohol. Even a couple of glasses noticeably press HRV down the same night. Watch yourself and you will see the link.
  • Gentler with load. A hard workout is fine, but the body needs time afterwards. HRV will tell you when you are ready again.

Do not chase a pretty number. Treat HRV as a friendly hint: push today — or ease off today.

Sources

  • A review of HRV metrics and autonomic norms — Shaffer F. et al., Front. Public Health, 2017. read
  • HRV rises with fitness and falls under overload — Plews D. et al., Sports Medicine, 2013. read
  • Evening alcohol measurably lowers night-time HRV — de Zambotti M. et al., Sleep, 2021. read

This is not a diagnosis and not a replacement for a doctor. If something about how you feel worries you, see a specialist.