How to improve HRV: what the research links to heart rate variability

What is HRV, and can you really improve it?

The Cleveland Clinic describes heart rate variability as a slight change in the time between your heartbeats.¹ That time is never perfectly even, and the amount of variation is what an HRV number summarizes. Our guide to heart rate variability and what the numbers mean covers the definitions. This page covers one question: what do the studies link to a higher or lower HRV?

The honest answer has three parts. Some habits are linked to HRV in controlled studies, and those links are real but modest. The size of the link differs between people. And a better number on a wrist band is not the same thing as better health, so this page makes no promise about outcomes.

The Cleveland Clinic lists several things that can lower HRV: lower quality or amount of sleep, stress, anxiety or depression, an increase in body mass index, and age, since HRV tends to get lower as you get older.¹ The sections below take the habits one at a time and say how strong the evidence is.

Does sleep change HRV?

Sleep is the factor with the most direct trial evidence on the downside. A systematic review and meta-analysis in Frontiers in Neurology pooled 11 randomized trials with 549 participants. After sleep deprivation, RMSSD fell significantly, while LF and the LF/HF ratio rose. The authors read that pattern as more sympathetic and less vagal activity.²

Two cautions come with that result. First, the trials compared normal sleep with deprived sleep, so they say less about whether a long night pushes HRV above your usual level. Second, SDNN and HF did not change significantly, and the authors call for standard measurement methods in future work.²

For length, the NHLBI says experts recommend that adults sleep between 7 and 9 hours a night.⁷ That is a general sleep target, not an HRV target. If you are curious how sleep structure fits in, see the guide to sleep stages and the page on how to improve sleep quality.

Does exercise raise HRV?

Regular training has the best-supported link to a higher vagal HRV signal. Sandercock and colleagues pooled 13 studies measuring high-frequency power (322 cases) and found an overall effect size of 0.48 with a confidence interval of 0.26 to 0.70. Twelve studies on the time between beats (298 cases) gave an effect size of 0.75.³ Both point to a positive training effect.

The same analysis shows why a personal number can disappoint. The changes were influenced by the age of the study population, and the response of the time between beats looked smaller in older people.³ An effect size is an average across groups. Your own change can be larger, smaller or absent.

A more recent meta-analysis asked a different question: does training guided by daily HRV beat a fixed plan? It found a small advantage for vagal-related HRV indices (SMD 0.50, confidence interval 0.09 to 0.91), but only small, non-significant differences for maximal aerobic capacity (SMD 0.20, confidence interval minus 0.07 to 0.47).⁶ The authors conclude that any group-level fitness advantage is by a small margin.⁶

For the amount of activity itself, see the published guide to VO2 max and our page on how to improve VO2 max, which cover the guideline amounts in detail. The Cleveland Clinic frames it simply: regular physical activity and healthy foods improve your overall health, which can help HRV.¹

How does alcohol affect HRV overnight?

A study in JMIR Mental Health followed 4,098 Finnish employees who wore a beat-to-beat recorder in normal life and reported their alcohol intake. The authors compared each person’s days with and without alcohol, looking at the first 3 hours of sleep.⁴ Alcohol intake was associated with more sympathetic regulation, less parasympathetic regulation and insufficient recovery, in a dose-dependent way.⁴

Two details matter for readers. The effect was seen even at low intake, and it was similar in physically active and sedentary people, so being fit did not protect against it.⁴ The effect was stronger in young than in older participants.⁴ The study cannot tell you how many drinks are right for you, and this page does not recommend an amount.

Stress, breathing and mental load

Kim and colleagues reviewed 37 publications on stress and HRV. In most studies, HRV variables changed in response to stress, and the most frequent finding was low parasympathetic activity, shown as lower high-frequency power and higher low-frequency power.⁵ The authors conclude that HRV is affected by stress and can support an objective assessment of psychological stress.⁵

The Cleveland Clinic draws the practical link: reducing and managing your stress level can improve HRV, and biofeedback training can teach you to control your breathing.¹ No pooled figure for breathing exercises was read for this page, so no number is given here.

A short HRV dip after a hard week is not unusual. A low reading is a prompt to look at the week, not a verdict. If low mood, anxiety or stress is weighing on you, the Cleveland Clinic notes that managing it can help HRV, and a clinician is the right person to talk to about how you feel.¹

How to read your own HRV trend

The Cleveland Clinic gives reference bands for a 24-hour measure (SDNN): below 50 milliseconds is unhealthy, 50 to 100 is compromised and above 100 is healthy. It stresses that these figures vary with age and should be interpreted by a healthcare provider.¹ Wearable bands usually report an overnight value from a different method, so do not set those bands against your tracker number.

The page also says that a smartwatch can detect HRV changes, that an EKG is more accurate, and that most wrist-worn trackers usually are not sensitive enough to detect HRV accurately.¹ It adds that numbers do not tell the whole story.¹ That is why your own trend, measured the same way, is more useful than a comparison with another person.

1. Choose one way to measure. Use the same device and the same moment each day, for example the overnight reading. Methods such as recording position and how a baseline is set are still being studied.⁶
2. Collect a run of days before judging. One value is noise. A week or more of readings shows your own range, and the Cleveland Clinic says normal differs from person to person.¹
3. Note what happened the day before. Write down a late night, alcohol, a hard workout or a stressful day. Those are the factors in the table above.²³⁴⁵
4. Change one habit at a time. If you change sleep, training and drinking in the same week, you cannot tell which one moved the number.
5. Judge by the trend and by how you feel. A small shift in either direction is expected. Numbers do not tell the whole story.¹

If you want to compare devices that report HRV, see the published guide to the best HRV monitors. For a related signal that is easier to measure, see how to measure resting heart rate.

What an HRV number cannot tell you

A wellness band reports an HRV estimate from its sensor. It does not tell you why the number moved, it does not show whether your heart is healthy, and it cannot replace a test ordered by a clinician. The Cleveland Clinic says low HRV can signal health problems and that a healthcare provider should interpret your results.¹

Frequently asked questions