Even if you don’t wear a smartwatch or fitness band to track your heart rate, you can often sense your pulse fluctuating throughout the day. During your waking hours, the number of heartbeats per minute when you’re just sitting quietly is known as your resting heart rate. In most adults, resting heart rates range between 60 and 100 beats per minute.
Once you stand up and move around, your heart rate goes up. And exercise boosts it further still. Even intense emotions — fear, anger, or surprise — can cause your heart rate to spike. But what happens when you lie down to sleep? The answer differs depending on the phase of sleep: light sleep, deep sleep, or rapid eye movement (REM) sleep.
How does your heart rate change while you sleep?
“During sleep, the stimulation of your nervous system is reduced and most of your body processes slow down,” says Dr. Lawrence Epstein, associate physician with the division of sleep and circadian disorders at Harvard-affiliated Brigham and Women’s Hospital.
Within about five minutes after you drift off to sleep, your heart rate gradually slows to its resting rate as you enter what’s known as light sleep. Your body temperature drops and your muscles relax. People typically spend about half the night in light sleep. But during the next phase, deep sleep, your blood pressure falls and your heart rate slows to about 20% to 30% below your resting heart rate.
When you dream, you enter the sleep phase known as REM (also known as dreaming sleep). “Your heart rate can vary quite a bit during REM sleep because it reflects the activity level occurring in your dream. If your dream is scary or involves activity such as running, then your heart rate rises as if you were awake,” says Dr. Epstein.
Can you change your resting heart rate?
If you run or do other moderate to vigorous physical activity regularly, you can lower your resting heart rate. That’s because exercise strengthens the heart muscle, allowing it to pump a higher volume of blood with each heartbeat. As a result, more oxygen gets delivered to the muscles, so the heart doesn’t need to beat as many times as it would in someone who is less fit.
As people age, the resting heart rate stays about the same unless they are taking medicines that slow heart rate, such as beta blockers or calcium channel blockers.
To determine your resting heart rate, try taking your pulse when you wake up a few days a week over the course of several weeks. With your index and middle fingers, press lightly on the opposite wrist, just below the fat pad of your thumb. Or press gently on the side of your neck, just below your jawbone. Count the number of beats over a period of 30 seconds. Double that number to get your heart rate in beats per minute. (Measuring for just 15 seconds and multiplying by four is also pretty accurate.)
A resting heart rate that is too low (less than 50 beats per minute), or one that is 100 or higher, could be a sign of trouble and should prompt a call to your doctor.