You’ve probably heard the term “heart rate” tossed around since elementary school P.E. Chances are, you’ve seen it, too—it’s that blinking number in the corner of your elliptical screen that increases the faster you pedal.

By definition, heart rate is the number of times your heart beats within a minute. But what else can it tell you besides how sweaty you’ll be at the end of your workout?

For one, it’s an important indicator of your cardiovascular health, or how efficiently your heart pumps blood, says Michael Souders, exercise physiologist at Integrative Cardiology and personal trainer at New York Health and Racquetball Club. Knowing your target heart rate can help you design workouts to meet your fitness goals and get back on track if something’s out of whack.

RESTING VS. ACTIVE HR

When you work up a sweat, your active heart rate rises to meet your workout’s demands. While you’re vegging out on the couch, your resting heart rate should be around 60 to 100 beats per minute, says Hina Chaudhry, M.D., associate professor at the Icahn School of Medicine at Mount Sinai Hospital in New York.

A low resting heart rate is actually a good thing, Souders says. “If your heart rate is lowering for a given intensity, then that means your heart is getting better at pumping blood,” he explains. With regular exercise, your active heart rate will decrease as your heart learns to work more efficiently. For example, trained athletes may have a resting heart rate as low as 40.

If you’re comparing FitBit or Apple Watch data with a friend, don’t worry if your heart rate is higher than your friend's, especially if that other person is male. Women typically have a higher resting heart rate than men due to size and hormonal factors, says Chaudhry. Even with equal training, a female athlete’s resting heart rate will be about 10 beats higher than that of a male athlete.

WHAT’S MY TARGET ACTIVE HR?

To calculate your maximum heart rate (a.k.a. the number of beats per minute you shouldn’t exceed, even in an intense workout), Souders suggests following The Centers for Disease Control and Prevention (CDC) formula (220 – your age). You should stay within 60 to 75 percent of that number to maintain a healthy active heart rate.

As crazy as it sounds, your heart shouldn’t beat every second, he says. Heart rate variability, or the time between successive heartbeats, indicates more effective heart function. To improve variability, he suggests high-intensity interval training, or HIIT. Working out within 80 to 90 percent of your active rate for a few minutes, then recovering at your resting rate repeatedly trains the heart to be more flexible (translation: that uphill run won’t be as brutal if you exercise at that level regularly, because your heart gets used to working that hard).

While heart rate monitors and fitness trackers offer instant data for those on a workout plan, they’re not necessary, Chaudhry says—taking your pulse will suffice! To check the pulse in your neck, place your forefinger and middle finger next to your windpipe and count the number of beats you feel in 15 seconds, then multiply that number by four. For the most accurate reading of your resting rate, take your pulse right after you wake up. To see the range of your active rate during workouts, monitor your pulse before your warm up, in between intervals, and after your cooldown.

Heart rate can also indicate improvement in physical fitness, even if the scale says otherwise. Participants in a weight-loss program may not see the body composition changes they want right away, Souders explains. But if they check their heart rate periodically throughout their program, they may see a lower heart rate—an indicator of improved heart function (and some gratification for all that hard work).

IS MY HR NORMAL?

If your pulse is higher than usual after a stressful day at work, Souders says not to worry. “It could be a clue to take it easy, lower the intensity or shorten the duration of your workout,” he says. Stay hydrated, too, Chaudry adds, as that can help calm you down and lower your heart rate.

If your heart rate is still nearing 100 beats per minute before you fall asleep, you should consult your doctor to check for a thyroid disorder or an irregular heartbeat.

WHAT ACTIONS CAN I TAKE?

The best advice for improving your heart function? “Do something,” says Souders. The American Heart Association recommends at least 150 minutes of moderate cardio activity per week (or 75 minutes of vigorous cardio, like HIIT). Whether it’s a cycling class or a leisurely walk with a furry companion, activity of any kind is enough to get your blood pumping.

“Exercise is the only fountain of youth we have,” Chaudhry advises. Working out regularly—and monitoring your heart rate throughout—will improve your cardiovascular health, no matter your fitness level.