There are tiny fluctuations in the pace of your heartbeat that shed light on mental health, stress, exercise capacity and even how well you’re aging. Those fluctuations are called heart rate variability (HRV).
As wearable health monitors, like smart watches and smart rings, become more common, people are tracking every aspect of their health. Some people use their HRV to determine their exercise or lifestyle for the day.
"You want a heart to beat more or less regularly," said Dr. Deepak Bhatt, director of the Mount Sinai Fuster Heart Hospital. Large variation can lead to stroke or heart failure.
But HVR measures variations between beats by the millisecond. Then, more variability is actually better, according to Dr. Bhatt. However, there isn’t a “best” HRV. It depends on a person’s age, sex, fitness level, tracking device and more.
While wanting high variability seems wrong, it’s because it’s a way to measure how well the nervous system switches between “rest-and-digest” and “fight-or-flight.” If you have to outrun a bear, your body goes into fight or flight. Your pulse rises so you can run faster, and your HRV drops because your heart has to be steady to keep up the pace. When you are resting, your HRV naturally speeds up and slows down during activities like inhaling and exhaling. Having a higher HRV means your body can correctly react to the situation it’s in. Having low HRV means the body gets stuck in modes.
“Heart rate variability refers to the natural variation in time between consecutive heartbeats,” said Dr. Michael Esco, professor of exercise physiology at the Univ. of Alabama. “It is largely driven by the balance between the parasympathetic — rest-and-recover — and sympathetic — fight-or-flight — branches of the autonomic nervous system.”
“A higher HRV means your heart is more adaptable, which is a sign of a well-functioning autonomic nervous system,” said Dr. Stefanie Broes, cofounder and CEO of moonbird, a handheld device that gives the user real-time HRV biofeedback. “A lower HRV often signals that your body is under stress, not recovering well or running low on resources.”
Fitness enthusiasts are using HRV to try to optimize their workouts. HRV should dip during a hard workout and rise as a person recovers. If it stays low instead of recovering after a workout, that may suggest a person needs more rest to recover from their routine.
HRV reflects mental as well as physical stress and may be used as an indicator of anxiety and depression. People with either condition often struggle with a constant state of stress. Other conditions, including PTSD, dementia and schizophrenia, often go hand-in-hand with a low HRV.
Top wearable brands, including Oura Ring and Garmin, are now stressing HRV. Tracking the number may help you get the most out of your workout. It may also help you listen to your body more clearly and shed light on your health.
