What is a good HRV? And why your breathing changes it
Short answer
There is no single good HRV. Heart rate variability depends heavily on age, fitness and genetics, and it falls gradually as you get older. A good HRV is one that is normal for you: stable or rising over weeks. A drop well below your own baseline is the signal worth paying attention to. Breathing has a direct effect on the number, because your heart speeds up when you breathe in and slows down when you breathe out.
HRV meaning: what heart rate variability measures
Heart rate variability (HRV) is the variation in time between one heartbeat and the next. A heart beating at 60 beats per minute doesn't beat exactly once a second. The gaps shift by a few milliseconds all the time. Most wearables report HRV as RMSSD, in milliseconds.
Higher variability generally means the parasympathetic, "rest and digest" side of your nervous system is in charge. Lower variability means your body is under more load: from training, stress, illness, alcohol or poor sleep.
What is a good HRV?
Comparing your HRV to someone else's tells you very little. Two healthy people of the same age can have nightly averages that are tens of milliseconds apart. What matters is:
- Your baseline. Your typical value over the last few weeks.
- The trend. Stable or slowly rising is good. A falling trend over several days means something is weighing on recovery.
- Sudden drops. A night well below baseline often follows alcohol, a late hard workout, illness or a bad night's breathing.
HRV by age
HRV is highest in young adults and declines gradually with age, so a 50-year-old will usually have a lower HRV than a 25-year-old with the same fitness. That is why a heart rate variability chart by age is only a rough guide. Track your own number against your own history.
Why breathing changes your HRV
Your heart rate rises a little each time you breathe in and falls each time you breathe out. This is called respiratory sinus arrhythmia, and it is one of the biggest sources of the variation that HRV measures.
That means your breathing pattern shapes the number directly. Slow breathing with a long exhale produces larger swings and a higher HRV reading. Fast, shallow breathing, which often comes with mouth breathing during sleep, gives a lower reading, even if your fitness and recovery haven't changed at all.
Breathing-regulated HRV
A wrist-based wearable sees your heartbeats but not the breathing underneath them, so it can't tell whether a low HRV comes from poor recovery or from a night of fast breathing. FLOU measures your breathing at the nose and reads HRV against your breathing rhythm. We call this breathing-regulated HRV. It helps you separate what is happening to your recovery from what is happening to your breathing.
How to improve your HRV
- Keep a regular sleep schedule
- Cut back on alcohol, especially in the evening
- Do regular aerobic training, with real recovery days
- Practise slow breathing, around six breaths a minute, with a long exhale
- Breathe through your nose at night. See nasal breathing benefits.
Frequently asked questions
What does HRV mean?
HRV stands for heart rate variability: the variation in time between consecutive heartbeats, usually measured in milliseconds. It reflects how much your nervous system is in a relaxed, recovering state.
Is a higher HRV always better?
Generally a higher HRV relative to your own baseline means better recovery, but comparing your absolute number with other people's is not very meaningful. Age, genetics and how it is measured all shift it.
Why is my HRV low?
Common reasons for a low HRV are alcohol, hard training without recovery, stress, illness, poor sleep and fast or irregular breathing during the night.
Does breathing affect HRV?
Yes, directly. Heart rate rises when you breathe in and falls when you breathe out, so slow breathing raises HRV readings and fast, shallow breathing lowers them.
FLOU is a wellness device. It is not intended to diagnose, treat, cure or prevent any disease. This guide is general information, not medical advice. Talk to a clinician about sleep-disordered breathing.