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HRV, or heart rate variability, measures how much the time between your heartbeats varies. A higher HRV usually means your body is well rested. In healthy adults, morning RMSSD most often falls between 20 and 80 ms and declines with age. The most important thing is to track your own 7-day average, not to compare yourself with others.
What exactly is HRV
Your heart does not beat like a metronome. Even at 60 beats per minute, there is not exactly one second between every two beats. Sometimes it is 0.95 seconds, other times 1.07. These tiny differences are HRV.
Your autonomic nervous system is behind them. Its "rest" branch, the parasympathetic system, slows your heart and increases the differences between beats. Its "alarm" branch, the sympathetic system, speeds up your heart rate and makes it more regular. When you are well rested, the rest branch dominates and HRV is higher.1
Wearables most often measure RMSSD in milliseconds. It is the standard for short measurements and captures the rest branch of the nervous system well.2
What is a normal HRV
A review of studies in healthy adults reports an average resting RMSSD of around 42 ms for short measurements. The typical range is roughly 19 to 75 ms.3 HRV naturally declines with age, most of all between 20 and 50.4
For overnight measurements with wearables, healthy people most often show roughly these ranges. These are not medical norms, just a guide:
| Age | Typical overnight RMSSD |
|---|---|
| 20 to 29 years | about 40 to 90 ms |
| 30 to 39 years | about 35 to 75 ms |
| 40 to 49 years | about 30 to 60 ms |
| 50 to 59 years | about 25 to 50 ms |
| 60 and older | about 20 to 40 ms |
Treat these numbers as a rough guide only. Differences between people are huge and depend on genetics, fitness, sex, and when and how the measurement is taken. Someone at 35 ms can be just as healthy as someone else at 90 ms.
Why you should only compare with yourself
Coaches of world-class endurance athletes don't look at a single morning reading. They track the 7-day rolling average and whether it stays within the athlete's usual range.5 Individual nights can swing by 20 to 30% for no obvious reason.
What to watch for:
- A stable average within your range: your body is handling the load well.
- An average below your range for several days: more stress, poor sleep, an illness coming on, alcohol or too much training.
- A sudden one-off drop: common after a hard workout, a heavy late meal or alcohol. If it bounces back within two days, you are fine.
What lowers HRV
- Alcohol. Even one or two drinks in the evening lower your overnight HRV. It is one of the most visible effects.
- Short or irregular sleep.
- Hard training without enough rest. A short-term drop is normal, a long-term one is not.
- Illness. HRV often drops a day or two before symptoms show up.
- Mental stress and heavy late meals.
How to increase HRV
- Sleep on a regular schedule. Go to bed and get up at the same time, weekends included. Adults need at least 7 hours of sleep.
- Train sensibly. Regular endurance and strength training raise HRV over the long term. Mix hard days with easy ones.
- Cut back on alcohol, especially in the evening.
- Breathe slowly. About 6 breaths per minute, so a 5-second inhale and a 5-second exhale, for 5 to 10 minutes a day. This supports the rest branch of your nervous system.6
- Move outside of training too. Steps and everyday movement help your heart as well.
Changes show up in your HRV gradually, usually over several weeks. That is why it pays to watch the trend, not individual days.
Frequently asked questions
Is a high HRV always good?
Usually, but not always. In rare cases, sudden very high values can be linked to an irregular heart rhythm. What matters is the trend within your usual range.
When is the best time to measure HRV?
Overnight while you sleep, or first thing in the morning after waking, always under the same conditions. Overnight measurement with a wearable is the most stable.
Why is my HRV different from my friend's?
HRV is shaped by genetics, age, sex, fitness and how it is measured. Differences of two to three times between healthy people are common.
How long does it take for HRV to improve?
After a night of drinking, it recovers in 1 to 3 days. Long-term improvement from better sleep and training usually shows up within 4 to 8 weeks.
References
- 1.Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Front Public Health. 2017;5:258. doi:10.3389/fpubh.2017.00258
- 2.Laborde S, Mosley E, Thayer JF. Heart rate variability and cardiac vagal tone in psychophysiological research: recommendations for experiment planning, data analysis, and data reporting. Front Psychol. 2017;8:213. doi:10.3389/fpsyg.2017.00213
- 3.Nunan D, Sandercock GRH, Brodie DA. A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing Clin Electrophysiol. 2010;33(11):1407–1417. doi:10.1111/j.1540-8159.2010.02841.x
- 4.Umetani K et al. Twenty-four hour time domain heart rate variability and heart rate: relations to age and gender over nine decades. J Am Coll Cardiol. 1998;31(3):593–601. doi:10.1016/S0735-1097(97)00554-800554-8)
- 5.Plews DJ et al. Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring. Sports Med. 2013;43(9):773–781. doi:10.1007/s40279-013-0071-8
- 6.Lehrer PM, Gevirtz R. Heart rate variability biofeedback: how and why does it work? Front Psychol. 2014;5:756. doi:10.3389/fpsyg.2014.00756
This article is for general information and does not replace advice from a doctor or registered dietitian. If you have a health condition, talk to a professional before changing your training, diet or supplements.
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