All About Heart Rate Variability and How to Track it

Your fitness tracker may be failing you if it doesn’t have this one key sensor that could help monitor stress, recovery, and workout readiness: a heart rate variability (HRV) monitor.

Don’t get this confused with your heart rate; it’s different. Heart rate (HR) monitors measure your beats per minute—a standard measure of exertion, which is why they’re ubiquitous, from your doctor’s office to your gym to your smartwatch. HRV, by contrast, measures the change in time intervals between adjacent heartbeats. This, research says, is a better re ection of the health of the body’s self-regulatory and autonomic nervous systems and its ability to adapt to challenges, changes, and stress.

Here’s how it works: The more variable your heart rate is from one moment to the next, the more quickly your body is responding to changes and stress—whether that’s exercise, a surprising loud noise, a bear chasing you, or a deep breath. Your body should be able to adapt quickly to these changing circumstances. And that high variability will be indicated by a higher HRV number.

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By contrast, if your heart rate is less variable from beat to beat, then your heart rate isn’t changing and responding to stress optimally. This low HRV may indicate, on the extreme, that you’re at risk of a cardiac event, and for most it could just mean you need a rest day.

HRV has been used since the 1960s in cardiology research to detect the possibility of a heart event (a heart attack, for example) in patients. These days HRV is fit for the masses because this relationship between stress response and HRV can help users take control of their future choices by knowing how responsive their body is (or isn’t) at the moment. HRVs represent the future of stress management and training—and can help you avoid overtraining.

Today HRV monitors are being rolled out in fitness trackers like the Garmin Vivoactive 3 and stand-alone devices like the Zoom HRV. Get one of these and never guess again how a stressful week is affecting you.

2 HRV Trackers We Love

1. Zoom HRV

Track your heart rate variability automatically while you sleep, train, work, repeat. Now you’ll know exactly when your stress level may get in the way of your day’s goals. The Zoom HRV app is unique in that you can log on and see your HRV tick forward in real time. It also analyzes sleep and heart-rate-based calorie burn and can show you a year’s worth of your deep data all in one place. Based on all its metrics, it’ll post a Fitness Score, showing you whether you’re in prime form to train. Knowledge is power.

($140; lifetrakusa.com)

2. Garmin Vivoactive 3

All the tech you need in one smart fitness watch: The Vivoactive 3 tracks 15 sports and has built-in HRV and VO2 max monitors, along with the industry standards of steps and heart rate. You already know what HRV can do, and the VO2 sensor assesses your maximal oxygen consumption, or the amount of O2 you use during high-intensity exercise—an excellent marker of aerobic endurance and cardiovascular health.

Plus, get phone notifications, weather, tons of digital “watch faces,” smart home controls, and tap-to-pay with Garmin Pay.

($300; garmin.com)

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