Make Heart Rate Variability Your Secret Anti-Stress Weapon

5 min read

Jan. 4. 2024 -- Just when you thought you had enough medical acronyms in your life (LDL, MRI, ACL, OMG-what’s-that-rash), another one is swirling around the #IYKYK ether: HRV.

HRV -- heart rate variability -- has shifted from a primarily clinical and research metric to a more mainstream one as a diagnostic found on many smartwatches.

Simply, HRV is a measure of the variation in time between your heartbeats and can be used as a guide to help manage stress. If you’re in fight-or-flight mode, for example, your heart pumps faster and time between beats becomes shorter. This reduces HRV and indicates higher stress.

“It’s an excellent data point and a reliable one,” said Leah Lagos, PsyD, a clinical psychologist in New York City who has worked on using HRV biofeedback for health and performance for nearly 20 years. “HRV is a measure of adaptability and resilience. In life, there’s stress all the time. It’s the ability to not have extreme reactions and recover quickly — essentially that’s what HRV is measuring.”

For many of us, HRV is sort of like GarageBand -- we know it’s on our phone, but heck if we know how to use it. Here’s what to know about HRV and how you can use it to help manage stress.

What Is HRV? 

Your autonomic nervous system is divided into two parts: sympathetic (which accelerates your heart rate to help you deal with stressful situations) and parasympathetic (which relaxes you so your heart can slow down). In extreme conditions, it’s easy to determine a fast heart rate (say, when you’re running) and a slower one (when you’re chilling). 

But second by second, there’s much more micro-level variation. 

“The cause of this HRV is explained by the fact that the two autonomic components are not activated continuously,” said Hugo C.D. Souza, PhD, associate professor at the University of São Paulo in Brazil who studies HRV. They work like power sources -- they’re either on or off. “Both autonomic components act alternately, with different frequencies of occurrence.”

The rate of your heartbeat, even if it seems steady, has small fluctuations in the milliseconds -- so minor that they’re undetectable without specialized devices. HRV measures those differences. 

Having a higher HRV -- or more variability -- indicates you’re more adaptable and better able to manage stress. A lower HRV -- or less variability -- means that the lines are more blurred between a high stress state and a high relaxed state.

How Can HRV Help Your Health?

HRV reflects more than your stress level. Research shows links between HRV and cardiovascular health, aging, anxiety, post-concussion health, and sleep quality. 

“Low HRV and an excessive dependence on the sympathetic autonomic component is a characteristic condition of many diseases and aging,” Souza said. 

One reason HRV and similar metrics have become prevalent in our wearable culture is because of the power these metrics can have.

“I think data accelerates behavioral change,” Lagos said, noting that how you “feel” often isn’t enough. “When you have data, it has a more significant impact on the response needed. From a psychological perspective, that’s an essential part of our new scaffolding for care.”

What’s the Best Way to Track Your HRV? 

2023 study showed that smartwatches have excellent accuracy for measuring HRV. Lagos recommends using one that’s been clinically shown to be reliable. (For example, studies have shown positive results for Garmin, Polar, and Apple.) 

Look at your HRV at the same time each day and in the same physical position to ensure consistency over time. It’s important to note that a low HRV doesn’t automatically mean you’re stressed out or at risk. Other factors like lack of sleep, alcohol use, and caffeine can influence it, Lagos said. The point is to establish a baseline so you can track changes and consider what variables may be affecting you. 

What’s a Good Number? 

A lot of factors influence HRV, including age, gender, and genetics, so it’s hard to identify an ideal range that applies to everyone. The “normal” HRV values you might find cited on the internet can vary widely and may not be reliable. Averages based on data from specific apps may not represent the general population, and HRV research studies show varying results. 

One 2020 study conducted in a large population -- more than 150,000 people in the Netherlands -- found average HRV values ranging from about 80 milliseconds (ms) in teenagers to 25 ms in older adults. (Previous research confirms that HRV decreases with aging, with the rate of decline slowing after age 60.) The study also showed that HRV tends to be a bit higher in women than in men; the average HRV for women 40 to 44 was 41, compared with 35 for men of the same age. 

Bottom line: Don’t get hung up on a “perfect score,” but rather use your data to find out what’s normal for you. Then track that value over time to see if your interventions are having an effect, Lagos said. 

“A higher HRV generally indicates a relaxed, recovered state, while a lower HRV can signal stress, fatigue, or overtraining,” Lagos said. 

How Do You Improve Your HRV? 

Studies show that regular exercise -- especially cardio like running, brisk walking, or cycling and coordination exercises like tai chi and dance -- can help improve HRV. In addition, studies have shown that resonant, deep breathing (breathing at a slow rate of about six breaths per minute) improves HRV. In one study, people practiced deep, resonant breathing for 20 minutes a day for 4 weeks; their HRV improved, and their perceived stress levels went down.

The importance, Lagos said, is that you’re training your heart just like a muscle (it takes some time to develop) to where you can optimize your HRV and “gain control in just a few breaths.” You might start with 20 minutes of resonant breathing 2 days a week for 20 minutes and then gradually increase from there.

What About HRV Beyond Stress?

Beyond the health implications, Lagos says, the next frontier for HRV may be centering on optimizing performance and relationships. A healthy HRV lets your parasympathetic system take over in stressful situations (like athletic competitions or public speaking), allowing you to work in a calm, relaxed, and creative state, essentially prolonging a “flow” feel, rather than an angsty one.

In addition, it can help improve personal and professional relationships because you can learn to morph from an agitated state to a calm one -- to work together and solve conflicts. Lagos says that her children, ages 5 and 8, even use it. In a conflict, one may say to the other, “Take two breaths,” Lagos said. “And they love it. They love feeling like they’re in control.”