Why Easier Efforts May Just Improve Your Cardiovascular Fitness

You may be focused on your legs, arms, and core when it comes to your workout. But you’re likely neglecting the one body part that may be the most helpful compass. An ever-growing body of research suggests that the organ in your chest—your heart—may be the best tool for gauging the intensity of your workout.

While there are many different types of cardio, zone 2 cardio (sometimes called “base training”) can build your aerobic fitness and increase your endurance—while keeping the strain on your body relatively low. In practice, this may look like a long run at a sustainable pace or a lengthy (yet relaxed) bike ride. Here, Peloton instructor Dr. Charlotte Weidenbach offers a crash course on zone 2 cardio, its benefits, and how to find this heart rate yourself. 

What Is Zone 2 Cardio?

“Zone 2 cardio” is one of the five heart rate zones, with five being the highest and one being (shocking, we know) the lowest, according to Dr. Charlotte. “[Zone 2] is at 60 to 70 percent of your max heart rate, so it's a low-intensity, basic endurance pace without intervals,” she says. Basically, it’s a slow, steady effort that you could maintain for a long time while having a casual conversation with a friend or singing a song to yourself.

Zone 2 training is sometimes called “base training” because it should make up the majority or “the base” of your weekly workouts. “Zone 2 training (and zone 3 training) should be the main focus of an endurance athlete, with 60 to 75 percent of the training week taking place in these zones,” Dr. Charlotte says.

Zone 2 training helps you build a foundation of fitness—no matter your modality. Over time, it  increases your aerobic capacity or your body’s ability to use oxygen efficiently during an athletic effort. Your easy workouts will eventually start to feel even easier, and harder workouts will feel, well, slightly less punishing. 

The Benefits of Zone 2 Cardio

At this point, you may be thinking, “Hmmm, I thought that hard, intense workouts offered the most when it comes to upping my heart health and endurance.” This common misconception may prompt you to push harder than you need to when you’re cycling, running, or participating in other forms of cardio. As a result, the benefits of this slower effort may surprise you. 

1. Faster Recovery

Throwing a zone 2 session in the day after a tough workout may actually help you recover faster. In a small 2022 study published in PLoS One, researchers found that this type of workout improves blood flow in the body, which speeds up muscle repair without causing additional inflammation and damage to the muscles. 

2. Increased Cardiovascular Fitness

"Aerobic training increases cardiovascular fitness, thereby reducing mortality, morbidity, and increasing longevity,” Dr. Charlotte says. “It reduces the risk of developing the most common cardiovascular illnesses like atherosclerosis, [which has] consequences like high blood pressure, stroke, and heart attack.” 

3. Better Mental Health

If you’ve ever blown off steam by taking a long run, swim, or bike ride, you won’t be surprised to hear that zone 2 cardio can improve your mental health. A 2019 study published in Health Psychology Research found aerobic exercise boosted the self-esteem and social functioning of participants and decreased their anxiety, depression, and insomnia. 

4. Injury Prevention

Zone 2 cardio takes less of a toll on your joints and muscles, potentially preventing injury as a result. By adding in a few easy days to your workout week, you’re giving your body plenty of time to rest and recover. Conversely, if you’re doing high-intensity interval training every single day, you may be placing unnecessary strain on your joints, increasing your chances of injury. “Zone 2 training should be the base for everyone doing endurance and also HIIT training,” Dr. Charlotte says. “Even weightlifters who normally avoid cardio can actually profit from building an aerobic base with zone 2 training.”

5. Sustainability 

Because zone 2 cardio doesn’t leave you winded, sore, and ready to crash on the couch for a while, you may find it easier to adhere to a workout routine that includes it. And research shows that those who find ease in their exercise routines are more likely to stick with them.

Heart Rate Zones, Explained

Now for the math part of zone 2 training. Don’t worry: Determining your zone 2 heart rate is easier than your high school algebra class. To start, you’ll need to calculate your max heart rate. 

How to Calculate Your Max Heart Rate

To discover your max heart rate (MHR), subtract your age from 220 (220 - x = your max heart rate zone). For example, a 30-year-old—let’s call her Suzanne—would have a max heart rate of 190 beats per minute. Once you have this number, you’re ready to find your heart rate zones. 

Determining Your Heart Rate Zones 

Zone 1: 50 to 60 Percent of MHR

Suzanne’s zone 1 heart rate (190 x .5

= 95 or 190 x .6 = 114) is 95 to 114 BPM.

You’ll see this heart rate in low-intensity workouts that don’t work your heart or lungs too much. A casual walk, easy stretching class, warm-up, or cooldown may place you squarely in zone 1. 

Zone 2: 60 to 70 Percent of MHR

Suzanne’s zone 2 heart rate (190 x .6 = 114 or 190 x .7 = 133) is 114 to 133 BPM.

As discussed, zone 2 is a comfortable effort that you can hold for a long time without strain or heavy breathing. In this state, your body uses both glucose and oxygen to propel itself forward. Think: a long, easy run on the Peloton Tread, a casual bike ride on your favorite path, or an energetic walk with friends. (This may even look like a recovery ride or run class.)

Zone 3: 70 to 80 Percent of MHR

Suzanne’s zone 3 heart rate (190 x .7 = 133 or 190 x .8 = 152) is 133 to 152 BPM.

“[Zone 3] is the upper end of aerobic training and the beginning of anaerobic training,” Dr. Charlotte says. The latter is an activity that uses glucose, but not oxygen, for its energy source. Your heart rate may move into zone 3 when you slightly increase the speed on your bike or up your running pace to about a seven out of 10 effort. 

Zone 4: 80 to 90 Percent of MHR

Suzanne’s zone 4 heart rate (190 x .8 = 152 or 190 x .9 = 171) is 152 to 171 BPM.

In this zone, you’re really starting to feel it. Your body starts to create lactate, a bi-product produced during intense exercise. If you’re working hard in a HIIT class and have trouble breathing and talking, congratulations, you’re in zone 4. 

Zone 5: 90 to 100 Percent of MHR

Suzanne’s zone 5 heart rate (190 x .9 = 172 or 190 ) is 171 to 190 BPM.

This is your maximum effort and likely one that you can’t hold onto for more than a few minutes. Throwing zone 5 training into the mix will help you build speed and power, Dr. Charlotte says. For example, you may opt for 30-second, all-out sprints at the end of an interval run or tack on a burpee finisher that leaves you gasping for breath. 

How to Start Training In Zone 2 

Remember: Zone 2 should account for the bulk of your training—60 to 75 percent of the runs, bike rides, swims, and HIIT training you do. “For beginners, it totally makes sense to only start with Zone 2 (and 3) training for a few weeks and build an aerobic base,” Dr. Charlotte says. “This [approach] has the benefit of not being overwhelming mentally and physically. It feels doable and can be much more fun if you're not used to pushing yourself!” 

As you become a more seasoned athlete, you can play with other heart rate zones. (Just make sure that this BPM-play doesn’t account for more than 40 percent of your training each week, or you may stumble into overtraining territory). “If you've been training for longer, zone 2 training is a great zone for long, low-intensity sessions that don't need much recovery afterward, as they're not very draining on your body,” Dr. Charlotte says.

An Important Note About Heart Rate Training 

While heart rate training can be a powerful tool for many people, it’s not infallible. Your sleep quality and quantity, stress levels, body size, emotions, and even medications can all affect your BPM. For example, you may be trying to work at a zone 2 (conversational) effort but notice that your heart rate is really in zone 3 or 4. Sometimes, you’ll have to roll with the punches and trust how you feel instead of looking at the numbers on your watch. 

If you find that your heart rate zones really don’t match your felt effort levels, make a point of seeing your doctor. They can help you determine what’s “normal” for you and why. 

And remember: Spending all your time staring at your heart rate may strip your workouts of every last ounce of joy. So, if you have an easy zone 2 effort on the schedule, consider letting yourself off the hook and going by vibes rather than numbers. In other words, er, follow your heart… but not too closely.