You finally committed to an exercise routine. You’ve got cushy sneakers and cool new leggings. You’re huffing and puffing your way to wellness. Then your health tracker mentions needing to hit your target heart rate and you’re not sure what that means.
No need to feel like an exercise newbie. Exercise physiologist Chris Travers, MS, explains heart rate zones — and if they really matter when you’re working out.
What are exercise heart rate zones?
Heart rate zones are a percentage of your maximum heart rate (heartbeats per minute). Exercise too close to your maximum HR (Mhr) and your heart and body will struggle to keep up with the demands.
“The goal of heart rate zones is to make you the most efficient, but to allow you to challenge yourself to improve cardiovascular fitness,” says Travers.
Exercise heart rate zones are the training levels based on your maximum heart rate. As you increase your pace, cadence and workload, you increase the demands on your heart. Travers breaks it down:
- Lower-intensity zone: You’re exercising at 50% to 60% of your max heart rate. At this point, 85% of the calories you burn are fat. The downside? You’re burning fewer calories overall than you would if you were exercising at a higher intensity. You’re generally able to sustain this zone the longest amount of time.
- Temperate zone: You’re exercising at 60% to 70% of your max heart rate. Roughly 65% of the calories you burn are fat.
- Aerobic zone: Working at 70% to 80% of your max heart rate puts you in the aerobic zone. About 45% of the calories you burn are fat. But you’re burning a higher number of overall calories compared to the other heart rate zones. You generally sustain this zone the shortest amount of time.
Why do you burn less fat the harder you work out? Travers explains, “Once your heart rate increases, you’re not taking in as much oxygen. You can’t oxidize fat fast enough. Your body turns to another, more readily available energy source to provide fuel for you — glycogen, also known as carbohydrates.”
How do heart rates affect workouts?
Heart rate zones let you know how hard your heart is working and what energy source you’re using — carbohydrates or fat. The higher your heart rate gets, the more you’re relying on glycogen from carbohydrates for fuel.
“For endurance athletes, it’s best to exercise in the zones that mostly rely on fat for fuel,” says Travers. “Fat is a longer-lasting energy source and better for longer, intense workouts.”
Best heart rate zone for fat loss
You’ll burn fat at every exercise heart rate zone. If you’re just starting to exercise, aim for the lower-intensity heart rate zone. As you build stamina, push yourself into the next zone until you’re comfortably at the aerobic level. That’s your heart getting stronger.
Cardio exercise is designed primarily to improve heart and metabolic health, says Travers. It helps lower your:
- Blood pressure.
- Cholesterol.
- Blood sugar.
For fat loss, he recommends strength training to build muscle. Having more muscle mass boosts your metabolic rate (the number of calories you burn while at rest), helping you burn more calories throughout the day.
“If you haven’t been active before, then cardiovascular exercise will help with weight loss in the beginning. But at some point, you’ll become aerobically fit,” Travers notes. “Then you won’t use as much energy (calories) to complete the same amount of exercise, so you’ll stop seeing significant weight loss.”
How do I find my target heart rate?
To find your target heart rate zone, you first have to know your max heart rate. The simplest way to determine that is to subtract your age from 220. That number is a general guideline for your max heart rate. Then multiply that number times the percentage listed in the exercise heart rate zone you want to be in.
For example, a 40-year-old woman has a max heart rate of 180 beats per minute (bpm). To exercise in the lower-intensity zone, multiply 180 times 50% or 60%. The target heart rate would range from 90 to 108 for a low-intensity workout.
Some exercise machines like treadmills automatically track your heart rate for you. But you can also track it yourself by wearing a heart rate monitor or fitness tracker.
What heart rate is too high?
Anything over your max heart rate is unsafe. But it’s also about duration, says Travers. You can do short bursts in a higher, more intense heart rate zone. Overall, though, it’s best to spend longer periods in a zone below your max heart rate.
“If you have heart disease, it’s important to learn target heart rates and monitor them as you exercise. For everyone else, the talk test works just fine,” says Travers. “Can you talk and carry on a conversation when you’re exercising? Then you’re in a heart-healthy, moderately easy zone. Don’t stress about the numbers.”
What matters most is that you make an effort to move more. Any exercise, for any length of time, will improve fitness. If tracking your heart rate makes you happy, then go for it. But if heart rate calculations become a stumbling block, forget about it. Your journey to becoming stronger and healthier is too important to let anything get in the way.
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A physical pursuit from Science Buddies
Key concepts The heart Heart rate Health Exercise
Introduction
Have you ever wondered how many times your heart beats in a day, a month, a year—or will beat in total throughout your life? Over an average lifetime, the human heart beats more than 2.5 billion times. For a person to keep their heart healthy, they should eat right, not smoke and get regular exercise. In this science activity, you'll measure your heart rate during different types of physical activities to find out which gives your heart the best workout to help keep it fit.
Background
A 150-pound adult has about 5.5 liters of blood on average, which the heart circulates about three times every minute. A person's heart is continuously beating to keep the blood circulating. Heart health experts say that the best ways to keep our hearts healthy is through a balanced diet, avoiding smoking and regular exercise.
Exercise that is good for your heart should elevate your heart rate. But by how much, for how long and how often should your heart rate be elevated? This has to do with how fit you are and your maximum heart rate, which, for adults, is about 220 beats per minute (bpm) minus your age. For example, if you are 30 years old, your maximum heart rate would be 190 bpm. The American Heart Association (AHA) recommends doing exercise that increases a person's heart rate to between 50 to 85 percent of their maximum heart rate. This range is called the target heart rate zone. The AHA recommends a person gets at least 30 minutes of moderate to vigorous exercise—exercise that elevates their heart rate to the target heart rate zone—on most days of the week, or a total of about 150 minutes a week.
Materials • Scrap piece of paper • Pen or pencil • Clock or timer that shows seconds or a helper with a watch • Comfortable exercise clothes (optional) • Simple and fun exercise equipment, such as a jump rope, bicycle, hula-hoop, two-pound weight, etc. Alternatively you can do exercises that do not require equipment, such as walking, doing jumping jacks, jogging in place, etc. You will want to do at least two different types of exercises, both of which you can sustain for 15 minutes. (Remember to always stop an exercise if you feel faint.)
• Calculator
Preparation • Practice finding your pulse. Use the first two fingers of one hand to feel your radial pulse on the opposite wrist. You should find your radial pulse on the "thumb side" of your wrist, just below the base of your hand. Practice finding your pulse until you can do it quickly. (You can alternatively take your carotid pulse to do this activity, but be sure you know how to safely take it and press on your neck only very lightly with your fingers.)
• Measure your resting heart rate, which is your heart rate when you are awake but relaxed, such as when you have been lying still for several minutes. To do this, take your pulse when you have been resting and multiply the number of beats you count in 10 seconds by six. This will give you your resting heart rate in beats per minute (bpm). What is your resting heart rate? Write it on a scrap piece of paper.
• You will be measuring your heart rate during different types of physical exercises over a period of 15 minutes. Choose at least two different exercises. Some examples include jumping rope, lifting a two-pound weight, riding a bike, hula-hooping, walking, etc. Gather any needed materials. (If you want to make a homemade hula-hoop, steps for doing this are given in the activity Swiveling Science: Applying Physics to Hula-Hooping .) Do you think the activities will affect your heart rate differently? How do you think doing each activity will affect your heart rate?
Procedure • Choose which exercise you want to do first. Before starting it, make sure you have been resting for a few minutes so that your heart is at its resting heart rate.
• Perform the first exercise for 15 minutes. While you do this, write down the number of beats you count in 10 seconds after one, two, five, 10 and 15 minutes of activity. (You want to quickly check your pulse because it can start to slow within 15 seconds of stopping exercising.) How do the number of beats you count change over time? How did you feel by the end of the exercise?
• Calculate your heart rate after one, two, five, 10 and 15 minutes of exercise by multiplying the number of beats you counted (in 10 seconds) by six. How did your heart rate (in bpm) change over time?
• Repeat this process for at least one other exercise. Leave enough time between the exercises so that your heart rate returns to around its normal resting level (this should only take a few minutes). How did you feel by the end of the second exercise? How did your heart rate change over time for this exercise?
• Take a look at the results you wrote down for this activity. Which exercise increased your heart rate the most? Which exercise increased your heart rate the fastest? Which exercise(s) elevated your heart rate to the target heart rate zone (50 to 85 percent of your maximum heart rate, where your maximum heart rate is 220 bpm minus your age)? Do you notice any consistent patterns in your results?
• Extra: Try this activity again but test different physical exercises. How does your heart rate change when you do other exercises? How are the changes similar and how are they different?
• Extra: Measure your heart rate while lying down, while sitting down, and while standing. How does your heart rate change with body position?
• Extra: Repeat this activity with other healthy volunteers. How does their heart rate compare to yours? How does their change in heart rate while exercising compare to how yours changed?
• Extra: Try this activity again but vary the intensity of your exercise. What intensity level elevates your heart rate to 50 percent of its maximum heart rate? What about nearly 85 percent of its maximum? Be sure not to exceed your recommended target heart rate zone while exercising!
Observations and results
After just a minute of exercise, did you see your heart rate reach its target heart rate zone? Did it initially jump higher for a more strenuous exercise, like hula-hooping, compared to a more moderately intense exercise, such as walking?
If you did a moderately intense exercise, such as walking, you may have seen an initial jump in your heart rate (where your heart rate falls within the lower end of your target heart rate zone within about one minute of exercise), but then your heart rate only slowly increased after that. After 15 minutes, you may have reached the middle of your target heart rate zone. To reach the upper end, people usually need to do a moderately intense exercise for a longer amount of time (such as for 30 minutes). If you did a more strenuous exercise—hula-hooping, for example—you may have seen a higher initial bump in your heart rate (such as reaching the middle of your target heart rate zone after just one minute of exercise), and then your heart rate stayed about the same for the remaining 14 minutes of exercise. Overall doing a more strenuous exercise generally raises a person's heart rate faster compared to doing an exercise that is only moderately intense.
More to explore
Target Heart Rates, from the American Heart Association
Cut to the Heart, from NOVA and PBS
Life's Simple 7—Get Active, from the American Heart Association
Heart Health: How Does Heart Rate Change with Exercise?, from Science Buddies
This activity brought to you in partnership with Science Buddies
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