Exercise Heart Rate Zones Explained

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 for 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 for 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, the 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.

Does the average person need to track their 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.