What To Know About Exercise and Heart Rate Zones

How intense was the workout you just finished? To truly answer that question, it helps to know your heart rate zones. This 1 to 5 scale reflects the effort and energy that you put into an activity.

Each zone is determined by a formula connected to your heart rate during an activity and offers different benefits for your body. But fair warning: It requires a bit of math to understand how it all works.

Let’s break down the numbers with the help of exercise physiologist Christopher Travers, MS.

What are heart rate zones?

Heart rate zones are essentially an indication of how hard your heart works to pump blood and keep up with the demands of what you’re doing, says Travers. It’s also a sign of what your body is burning for fuel.

Understanding target heart rate zones and what each offers allows you to tailor workouts to hit specific fitness goals, such as:

• Better cardiovascular fitness and endurance
• Fat burning and weight loss
• Building strength
• Reducing injury risk

“Certain heart rate zones bring certain benefits,” explains Travers. “Which one you’re in during a workout says a lot about what you’re going to get out of it.”

The five heart rate zones

There are five heart rate zones, ranked 1 to 5. A higher heart rate puts you in a higher heart rate zone. That may seem simple enough. But it’s not the whole story when it comes to setting your zones.

The reason? Each zone is based on a percentage of your maximum heart rate during exercise, or the highest number of times your heart can beat in 60 seconds. This number varies from person to person based on age, fitness level and other factors, says Travers.

Here’s a basic rundown of each zone.

• Zone 1: Low to moderate intensity at 50% to 60% of your max heart rate. You can easily hold a conversation. You’re typically in this zone while warming up and cooling down, or during a relatively easy workout. It’s ideal for a recovery workout, too.
• Zone 2: Moderate intensity at 60% to 70% of your max heart rate. A light conversation is possible, though you might need to stop here and there to catch your breath. Target this zone for longer cardio activities to build endurance or a light workout to limit injury risk.
• Zone 3: Moderate to high intensity at 70% to 80% of your max heart rate. Chatter will be at a minimum as your breathing intensifies. A workout in this zone is challenging yet sustainable, or comfortably hard. Good for building strength and endurance.
• Zone 4: High intensity at 80% to 90% of your max heart rate. Talking takes effort. You’re pushing hard and approaching a redline effort to boost speed and strength. Workouts in this zone should be limited to one or two times a week.
• Zone 5: Very high intensity at 90% to 100% of your max heart rate. Gasp! You’re trying to breathe, not talk. This would be a max effort activity. These exercises strengthen your heart by forcing it to work at peak capacity while also building fast-twitch muscle fibers.

If you’re trying to lose weight, it’s best to exercise with your target heart rate in zones 1 to 3. That’s because your body burns stored fat to fuel itself while doing those lower-intensity activities, says Travers.

Higher-intensity activities in zones 4 and 5, on the other hand, use your body’s glycogen (carbohydrates) and protein reserves to power through the session.

How to calculate target heart rate zones

The most basic way to estimate your max heart rate and set your heart rate zones is by using a basic age-adjusted formula. Don’t worry! It’s relatively easy math:

220 – your age = your max heart rate

So, for example, if you’re 40 years old, your max heart rate would be 180 beats per minute (BPM). (To show the math, as teachers always ask: 220 – 40 = 180.)

From there, a 40-year-old’s target heart rate for each zone follows the assigned percentages:

• Zone 1: 90 to 108 BPM (50% to 60% of 180)
• Zone 2: 108 to 126 BPM (60% to 70% of 180)
• Zone 3: 126 to 144 BPM (70% to 80% of 180)
• Zone 4: 144 to 162 BPM (80% to 90% of 180)
• Zone 5: 162 to 180 BPM (90% to 100% of 180)

Of course, not all 40-year-olds — or 20-year-olds or 60-year-olds, for that matter — are at the same level of fitness. Your actual max heart rate could be higher or lower than what this formula spits out.

“Not everyone has the same heart rate max or work capacity, so err on the side of caution when trying to reach zones,” recommends Travers. “The lower zone number may actually be your max for that zone.”

Other formulas — including the more complicated heart rate reserve formula, or Karvonen method — may provide a more accurate max heart rate number. (“Using a Karvonen calculator may give you a better idea of target zones once you establish a baseline,” notes Travers.)

The most accurate way to know your max heart rate is through an exercise stress test or a VO2 max test. During the test, you’ll be monitored while running as fast as possible on a treadmill or pedaling on an exercise bike. The heart rate you achieve at your “breaking point” is your max.

How to determine your heart rate

Many smartwatches include heart rate monitors that offer instant data as you’re working out or just sitting on the couch. (That idle time rate would be your resting heart rate, by the way.)

You can also go “old school” and find your heart rate by feeling your pulse on your wrist. Count the number of pounding thump beats in 30 seconds and then double that number for your heart rate.

Final thoughts

It’s best to chat with a healthcare provider before setting up an exercise program and determining target heart rate zones, especially if you have underlying health issues. Find out what’s safest for you.

“Make sure you check with your doctor before starting any new exercise program,” advises Travers. “Don’t be worried too much about heart rate numbers right away either. Just start slow and focus on building an exercise habit.”