Understanding Heart Rate Zones: Training Smarter for Cardiovascular Health

You probably know that when you exercise, your heart beats faster. But how fast should it beat? The answer depends on your age, overall fitness, and personal goals. 

J. Sawalla Guseh, MD, a Mass General Brigham sports cardiologist and director of the Cardiovascular Performance Program at Massachusetts General Hospital, explains that your heart rate is a key metric for improving your fitness. Dr. Guseh is also the team cardiologist for the New England Patriots and New England Revolution, bringing expertise in training for athletic performance and cardiovascular health.

“Heart rate zones are a complex topic, and there are many different models for calculating them,” Dr. Guseh says. “Because individual heart rates vary so much, no single formula works for everyone. It’s important to understand your personal response to exercise rather than rely solely on generic zones and calculators.”

Understanding the five heart rate zones

The five-zone heart rate model is one of the simplest to understand. Each zone maps to your exercise intensity:

• Zone 1: Very light effort
• Zone 2: Light effort
• Zone 3: Moderate effort
• Zone 4: Heavy effort
• Zone 5: Maximum effort

Some calculators estimate your five zones based on your age. However, these calculators fail to factor in your overall fitness, medical conditions, and environment, all of which impact your heart rate. A more reliable method is to use how exercise feels:

• In Zone 1, conversation is easy and you can sing.
• In Zone 2, you can speak in sentences but can’t sing.
• In Zones 3 to 5, speaking becomes difficult or impossible.

Physiologically, Zone 2 often corresponds to what many call the first lactate threshold, explains Dr. Guseh. “Crossing this metabolic threshold means your body begins producing more acid than it can easily expel in the form of carbon dioxide. You have to breathe faster, so speaking becomes more difficult.”

How do you find your cardiovascular training zone?

In sports cardiology, athletes often calculate their personal heart rate zones with a VO₂ max test. This test measures the maximum amount of oxygen your body can use during exercise. VO₂ max testing allows clinicians to customize heart rate zones to your body rather than relying on generic formulas.

So, which heart rate zones improve cardiovascular fitness most effectively? The evidence shows that any form of exercise you can do regularly will improve your fitness and lower cardiovascular risk. The best routine is the one you can sustain. For most people—and especially those at risk of cardiovascular disease—what’s called a pyramidal approach makes sense:

• 80% of your weekly workouts should be lower intensity, aiming for zones 1 to 2.
• 20% of your weekly workouts should include higher-intensity sessions.

This routine builds cardiovascular health and minimizes recovery time while still offering significant benefits. It’s also easier to stick to long-term.

“High-intensity interval training (HIIT) can raise VO₂ max and is a great form of exercise,” Dr. Guseh explains, “but recovery can be challenging. If you do too much, you may end up exercising less overall, which limits long-term benefit.”

How to use your pulse to estimate heart rate zone

When you understand heart rate zones based on exercise intensity, you can estimate your heart rate zone when you exercise. To do this, you’ll need to use a wearable activity tracker or check your pulse:

1. Place your first two fingers on the inside of your wrist, closest to your thumb.
2. Press lightly until you feel your heartbeat.
3. Count your heartbeats for 30 seconds, then double that amount to calculate your beats per minute (bpm).

How much exercise should you get for cardiovascular health?

The American Heart Association recommends at least 150 minutes of aerobic activity per week. Additionally, you should perform resistance training at least twice a week for bone density, muscular strength, and overall function.

Research has shown that cardiovascular benefits continue the more you exercise and the less sedentary time you have. For example, getting around 8,000 steps daily has been shown to reduce cardiovascular risk and all-cause mortality. Additionally, more exercise can have significant cognitive benefits, with another study showing a lower dementia risk in people who reached around 9,800 daily steps.

Signs cardiovascular fitness is improving

When your cardiovascular fitness improves, you’ll notice that your heart rate is lower than it used to be. For example, you may have previously run a 10-minute mile at a heart rate of 150 bpm. Now, you may be able to run the same pace at 140 bpm.

Your resting heart rate, the number of times your heart beats per minute at rest, may also lower. A standard healthy heart rate is between 60 and 100 bpm, although it’s normal for athletes and people who are in strong aerobic shape to have a lower resting heart rate.

“In general, consistent exercise reduces your risk of cardiovascular disease, heart attacks, and death. If you have cardiovascular risk factors, it’s always good to speak with your doctor before starting a new regimen. For most, aim for 150 minutes of exercise or more, and pepper in those high-intensity workouts once or twice a week,” says Dr. Guseh.