No matter what you do, your heart faithfully meets the demand by adjusting the speed at which it pumps out blood. It ramps up the action when you're pounding out miles on the trail, and dials it back when you're settling in for sweet dreams. Your heart rate is simply a measure of the number of beats per minute.
"It's your body's natural way of pumping oxygenated blood and nutrients to your muscles and other organs," says Michele Olson, PhD, researcher and professor of exercise science at the University of Alabama at Montgomery. "How fast or slow your heart is beating depends on whether your body's demands are low, such as at rest or during sleep, or if you're exercising vigorously and have an increased need for a faster supply of oxygen and nutrients."
The "Normal" Heart Rate
Each day, your heart beats approximately 80,000 to 110,000 times, at an average rate of 60 to 80 beats per minute. But there's no standard normal heart rate because a lot of variables can influence it, including your sex, age, and fitness level, to name a few.
"Women, for example, have smaller hearts and tend to have higher heart rates at rest and during exercise than men," Dr. Olson says. And the higher your fitness level, the lower your heart rate will go as it gets more efficient at delivering the same amount of blood and nutrients to organs and muscles. Researchers found that runners, for example, had a lower resting heart rate than inactive people in a small 2014 study.
What Causes Changes in Heart Rate
Our internal alarm — aka the "fight or flight" response — is regulated by the sympathetic nervous system and increases our heart rate to help us respond to physical and emotional demands and threats to our safety – from meeting a tight deadline to running for cover in a storm. The parasympathetic nervous system (dubbed the "rest and digest system") helps us recover from those demands or threats once they've passed, or wind down when it's time to rest by slowing down the activity of the heart and other vital organs.
"Heart rate is also modified by circulating hormones called catecholamines that are released during stress, happiness or exercise," explains Emad F. Aziz, DO, cardiologist and electrophysiologist at Mount Sinai St. Luke's Hospital in New York City. While exercise temporarily increases heart rate during the activity itself, it can help lower your resting heart rate over time. "Regular exercise is the best way to maintain a normal range of heart rate and heart rate responses."
In a study published in PLoS One in 2012, researchers found even if one's resting heart rate is high, regular physical activity can help offset the negative effect on the body's use of oxygen.
How to Check Your Heart Rate
To measure your heart rate, place two fingers between the bone and tendon where your thumb meets your wrist (the radial artery), or on the side of your neck, just below your chin and to the side of the Adam's apple. Once you detect your pulse, count the number of beats for 15 seconds, then multiple by four to get your total beats per minute.
"There are also numerous gadgets, like wristbands and phone apps... that can measure the heart rate with decent accuracy," Dr. Aziz says.
To get an idea of your resting heart rate so you can see whether it changes over time – say, after committing to a regular exercise routine – measure it while sitting comfortably. Make sure there aren't any distractions and it's not during a stressful moment or right after being active.
If you ever suspect that your heart rate is unusually high, low, or irregular compared to your typical resting heart rate, see your doctor just to be safe.