Heart rate variability could be the key to improving your body's response to stress. Here's how to get started

Kate, age 38, a finance analyst in Manhattan who requested the use of her first name only for privacy, learned that HRV refers to the time gaps between each heartbeat. Although the heart feels like a steadily beating drum, there are tiny changes in the lengths of these intervals, and people with more variation between each heartbeat tend to have better physical and emotional health.

New technologies are making it easier to measure and perhaps increase your HRV, and some of the companies behind them are joining forces.  

What is HRV

The time in between heartbeats changes due to a balancing act between two branches of the nervous system that control some of the body’s most important activities. The sympathetic branch carries signals that help us respond to stressful challenges; it increases heart rate, sweating and other automatic, “fight or flight” reactions. The second branch, called parasympathetic, exerts the opposite force, slowing down the heartbeat when we need to rest.

Even when you’re not active or recovering, these two branches stay busy with every breath, speeding up your heartbeat during inhales and slowing it down as you breathe out. The more quickly your heartbeat changes in both directions, the higher your HRV, suggesting the nervous system is well balanced, capable of easily ramping up your energy and heart rate when needed—while running a 5K, for example—and just as good at helping you wind down right after the race or any other physical or emotional stressor. 

Think of HRV like a tennis player, balancing weight from one foot to the other before returning serve. High HRV suggests you can head gracefully in either direction, primed to handle whatever life smacks your way.

Just as long as your HRV isn’t too high. “A person’s HRV is very individual,” says Tim Roberts, vice president of science and innovation at Therabody, which makes voice-guided breathing sessions for raising HRV. “You don’t want the trend to be too far out of your normal range.”

Lower HRV has been associated with shorter lifespan, obesity, cardiovascular disease, inflammation, mental health problems,  and viruses. 

Jessilyn Dunn, assistant professor in biomedical engineering at Duke,  found that HRV may drop when people get Covid-19, flu, or the common cold.  “There’s a combination of changes in HRV, resting heart rate, movement and sleep that together create a signature of infection,” Dunn says.

How lifestyle affects HRV

Roberts emphasizes that HRV is “just one factor” in monitoring health, along with getting regular blood panels and physical screenings. But it’s an important one, he says—and the good news is that we can control a variety of lifestyle factors that affect HRV. It’s also easy to measure through devices and apps.

In September, Therabody made its HRV breathing sessions, called TheraMind, available on the Oura app. Wearers of Oura Rings can see how their HRV changes after they’ve used these sessions, and as they adjust habits such as sleep and exercise. Oura Ring sensors are best for tracking HRV overnight, while moving your hand while awake could skew the measurement. For daytime readings, some prefer Polar chest straps that don’t require staying still.

The best way to find your personal range for HRV is to measure it as part of your daily routine, at the same time of day, for a few months. Because so many factors can affect HRV on any given day, you’ll want to jot down your daily number along with any issues that might be skewing HRV high or low, like having a stressful day at work or fighting a cold. Then you can look back over several months to determine your baseline HRV, or what’s normal for you. 

Your HRV isn’t necessarily stuck in stone, though; research points to several “interventions that amplify the body’s natural recovery responses,” Roberts says.

For example, regular exercise “really helps your body maintain homeostasis,” he explains, potentially raising HRV. Nutrition is another factor, with studies finding that HRV goes up for many individuals when following diets that are rich in fruits and vegetables or intermittent fasting. The reason could be that these diets may cut down on inflammation more than other eating plans; high inflammation can send the sympathetic nervous system into overdrive, reducing HRV. And proper hydration throughout the day could raise HRV—water, that is. Roberts’ own HRV drops after a few beers, a finding that’s been observed in several studies.

HRV is also affected by boosts in emotional well-being. Researchers see HRV tick up when people focus on pleasant memories. Psychologist Leah Lagos enjoys taking her kids to school so much that her HRV stays high the rest of the day. After observing this effect in her Oura app, she gives them rides more often. 

Despite these associations, researchers still aren’t sure about direct causation. Many factors, such as stress reduction and fasting, may improve sleep to elevate HRV. Therabody now markets several products, including its Theragun massager, for raising HRV through enhanced sleep.

How breathing affects HRV

Polar’s sensor, when used with apps such as Elite HRV, displays HRV in real time, showing how certain breathing practices affect it.

Paul Lehrer, a Rutgers psychologist, has spent three decades studying HRV biofeedback and its benefits. The first step in Lehrer’s protocol is to figure out something called your resonance frequency: the precise pace of breathing that syncs with your heart rate.

To find your resonance frequency, you’ll want to lengthen each inhale and exhale for a total breath lasting about 11 seconds. The inhale-exhale ratio differs for each person, but it’ll be somewhere around four seconds in, seven out. Breathing this way will widen the gap between your fastest heart rate, when you’re inhaling deeply, and your slowest heart rate, as it drops during the long exhale. Viewing the Elite HRV app, you’ll learn the pace of inhales and exhales that delivers your highest HRV.

“I can change your HRV within a few minutes of training,” Lehrer says. Then, “something very special happens.” He’s found that breathing at resonance frequency for 20 minutes, twice per day, over a period of ten weeks, is associated with major benefits, such as less depression, cravings for drugs and anxiety.

And, in Kate’s case, fewer migraines. She likes HRV biofeedback more than meditation, which made her too mellow. “I’m Type A and naturally anxious, but that helps make me successful,” says Kate. “Now I can harness that anxiety and control it to my benefit, versus letting it control me.”

The benefits may extend to cognitive performance, studies show, including better emotional regulation. The heart-brain connection is hardwired through the vagus nerve and, by controlling the heart through breathwork, “you change the body to change the brain,” Lagos says. She’s guided pro athletes and business leaders through sessions to improve HRV, post-concussion syndrome, recovery and performance.

While the Polar strap sells for $90, a more expensive sensor made by HeartMath promises more. Called Inner Balance, it clips to your earlobe, and its software encourages you to breathe at resonance frequency while enjoying pleasant thoughts, images and music. With sessions of 15 minutes daily, you can practice getting into a state of calm arousal, according to HeartMath’s research spanning 25 years. “Relaxation by itself is wonderful, but it’s not a high performing state,” says Deborah Rozman, a psychologist and HeartMath’s founding executive director.  

Lagos agrees that HRV biofeedback can help users access this peaceful, focused state, also known as flow—with practice. Her 10-week program is available through Elite HRV and described in her book.

“HRV is definitely trainable,” says Dunn, the Duke researcher. However, she cautions that genetics, age and biological sex can limit one’s range (women and older people tend to have lower HRV), and wonders if cognitive benefits from HRV biofeedback could simply come from “circulating more oxygenated blood to your brain” during deep inhales, just like other breathing practices.

Plus, how many people have time for this training? “It’s not really convenient for our daily lives,” Dunn says.

In recent years, though, access has improved. Cellphone cameras have proven surprisingly accurate in measuring HRV—no need to buy a separate sensor. Meanwhile, Dunn is exploring how HRV could be embraced by the healthcare establishment—one day. “HRV is on the lower end of measurements that clinicians feel are worth looking into,” Dunn says. “Its actionability isn’t totally clear at this point, but as we learn more about it, that will probably change.”