What is a good HRV?

The short answer

Heart rate variability, or HRV, is the small change in timing from one heartbeat to the next, usually measured in milliseconds. If you’re new to it, start with what HRV is and what controls it.

Harvard Health says there isn’t a recommended HRV value, because it varies so much with age, sex, fitness, health and genetics. Cleveland Clinic makes the same point: HRV gets lower with age, and a value that’s normal for one person may not be normal for someone else. So the most useful question isn’t whether your number is good. It’s whether your number is normal for you, and which way it’s moving.

Typical ranges by age

One of the most quoted studies, by Umetani and colleagues, recorded 24 hours of heartbeats in 260 healthy people aged 10 to 99. The table shows RMSSD, a common HRV measure that looks at the change from one beat to the next.

Averages are for each decade. Ranges are the study’s 95% limits at ages 20, 30, 40 and so on. Source: Umetani and colleagues, 1998.

Two things stand out. The ranges are wide: a healthy 30-year-old could sit anywhere from the high teens to the 70s. And the fall with age is steep at first. In the same study, RMSSD dropped to about half of its teenage level by the sixth decade and then levelled off. Below the age of 30, women’s HRV tended to be lower than men’s, and the difference faded with age.

Shorter recordings give similar pictures. A review of 44 studies by Nunan and colleagues found that 5-minute RMSSD in healthy adults averaged 42 ms, with figures across studies ranging from 19 to 75 ms. A study of more than 8 million Fitbit users also found that HRV falls with age. Among women aged 40 to 41, RMSSD measured between 6am and 7am averaged around 38 to 43 ms, with a lot of spread either side.

Why your number may not match a chart

Most HRV charts online come from a particular method, device and time of day. If any of those differ from yours, the comparison falls apart.

• The method. Apple Health records HRV as SDNN, which looks at the overall spread of beat timings, while the table above uses RMSSD. The two give different numbers for the same heart.
• The length of the recording. Shaffer and Ginsberg note that short readings and 24-hour readings aren’t interchangeable. A 24-hour SDNN of 100 ms or more is common in healthy people, but that bears no relation to a short reading from a watch.
• The time of day. The Fitbit study found a strong daily rhythm in HRV, so a night-time average and a midday reading aren’t comparable.
• The sensor. Harvard Health notes that chest straps tend to measure HRV more accurately than wrist devices.

The studies themselves have limits too. Umetani’s group was small for each decade, and the people in large wearable datasets aren’t a random sample of the population. Treat any table as a rough map, not a standard to meet.

Why your own trend matters more

Because people differ so much, a change from your own usual tells you far more than where you sit in a population. Researchers who study endurance athletes, such as Plews and colleagues, argue for monitoring HRV over the long term and looking at averages over a week or so, rather than reacting to one morning’s number.

A drop below your usual for a day or two often follows something ordinary. Cleveland Clinic lists stress, lack of sleep and ageing among the things that lower HRV, and Harvard Health adds lack of exercise and an unhealthy diet. A reading that stays below your usual for several days, especially if you also feel run down, is more worth noticing.

Higher isn’t automatically better either. Shaffer and Ginsberg point out that some health conditions can produce high HRV, and Harvard Health advises against reading too much into one high or low result.

Can you change your HRV?

The habits that tend to help are the familiar ones: regular activity, enough sleep and managing stress. In the Fitbit study, people who took more steps a day tended to have higher HRV across every age group. That study looked at a single moment rather than following people over time, so it shows a link, not proof that more steps will raise your number.

An HRV reading from a watch can’t diagnose anything. The British Heart Foundation advises seeing a GP if your heart rate is fast and you have symptoms such as dizziness, fainting or a fluttering feeling in your chest, and contacting your doctor if you’re worried about your heart.

Vital gives general information about fitness and wellbeing. It is not medical advice, and it does not diagnose or treat any condition.