In middle school P.E. class, my teacher taught me how to measure my own heart rate. I remember the moment being kind of magical. It was a brand-new way to take ownership of my own health and wellness, and I found myself taking my pulse in spare moments. You know, just for kicks. Now, it’s 2019—and if you have an Apple Watch, BPMs are just one of countless heart metrics your wearable is constantly recording.

It’s fun to set aside an hour or so to learn the full span of what the Apple Watch can teach you about your own ticker. If you want to skip the homework and head straight for the heart measurement that matters the most though, Jennifer Haythe, MD, director of cardio-obstetrics and internist at NYPH/Columbia, says to look no farther than your resting heart rate.

Your resting heart rate, as defined by the American Heart Association (AHA), is “the number of times your heart beats per minute when you’re at rest.” When you’re in the middle of a high-intensity workout, your pulse with quicken in your chest. But Dr. Haythe says that how it sounds when you’re doing, well, nothing tells a story of your overall health.

“A person in excellent physical condition will have a low resting heart rate—50-70 BPM—and will return to baseline quickly after exercise,” she tells me. “This is because a fit heart has a larger stroke volume [or, a higher amount of blood pumped out of the heart per beat], so the number of beats necessary per minute to perfuse the body is reduced.” Heart’s with higher stroke volumes don’t have to beat as frequently to maintain a normal cardiac output.

Scientific research also emphasizes the importance of having a low resting heart rate. Studies have linked higher resting heart rates with lower physical fitness, as well as higher blood pressure and body weight. According to the cardiologist, being aware of your resting heart rate can also help you realize when something in your body isn’t quite right. “For older people, an excessively low resting heart rate—30-50 BPM—may signify a conduction problem and possibly a need for a pacemaker or a medication adjustment if the person takes medications that may affect heart rate,” she says. Or, if you find yourself having an irregular heart rate when your body’s at rest, it could mean you need to visit your physician.

To train your way to a lower heart rate, the AHA recommends noting your target heart rate zone based on your age: “If you’re just starting out, aim for the lower range of your target zone (50 percent) and gradually build up. In time, you’ll be able to exercise comfortably at up to 85 percent of your maximum heart rate.” All that data can be found right on your wrist in the Apple heart app, so you don’t have to skip a beat to take your pulse.

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