What Is Zone 2 Cardio and Should I Do It?

Zone 2 cardio puts “steady state” into “steady state cardio.” It’s not as flashy as high-intensity interval training (HIIT) or as dramatic as bonking, but it’s just as noteworthy.

Zone 2 cardio is the foundation of any fitness routine, whether you’re an endurance athlete looking to improve your performance or just someone who wants to become a healthy, functional person.

So if you notice a “trend” regarding this type of exercise, be aware of this. Low-intensity steady-state aerobic exercise (LISS aerobic exercise) is always present. And if it hasn’t been part of your exercise routine before, it’s time to change it.

What is Zone 2 Cardio?

Zone 2 aerobic exercise refers to a specific intensity of exercise that can be sustained for an extended period of time, during which your heart rate is approximately 60-70% of your maximum heart rate. (Maximum heart rate is the number of times your heart beats per minute when you’re doing your best, such as sprinting the final distance of a 5K. We’ll talk more about how to determine your maximum heart rate later.) In this zone, you may be breathing slightly, but you’re not gasping for air.

There are five heart rate zones, each with a target range based on a percentage of your maximum heart rate (MHR). Below is a general breakdown of heart rate zones, but please note that these numbers are estimates and may vary depending on the source and person.

zone	strength	% of MHR
zone 1	low to moderate	50%～60%
zone 2	Moderately	60%～70%
zone 3	Medium to high	70%～80%
zone 4	expensive	80%～90%
zone 5	very high	90%～100%

Z1 2 Benefits of aerobic exercise

Like other aerobic exercises, Zone 2 aerobic exercise strengthens heart health and reduces the risk of cardiovascular disease. Steady-state cardio also burns calories, making it an effective tool for weight loss and healthy weight management. Zone 2 cardio (and exercise in general) also has a positive impact on your mood and mental health, and can improve your sleep quality.

But aerobic exercise, which keeps your heart within Zone 2, also offers some unique benefits, especially for endurance athletes looking to improve their performance. Here are a few:

1. Increase in mitochondria

If it’s been a while since you took a biology class, take a quick refresher on what mitochondria are and why they are important for athletic performance.

Mitochondria are a type of organelle within the body’s cells that use oxygen to produce adenosine triphosphate (ATP). ATP is the primary energy source that fuels physical activity and basic biological functions. More mitochondria means more ATP and therefore more energy for physical activity.

Dr. Todd Buckingham, exercise physiologist at PTSportsPRO in Grand Rapids, Michigan, describes zone 2 aerobic exercise as “ideal for mitochondrial development.” When you work out for long periods of time at a sustainable intensity, your cellular energy demands increase, and your body adapts to this demand by producing more mitochondria.

Therefore, for athletes who want to improve their endurance (or feel better during and after training), zone 2 cardio is essential.

2. Development of capillaries

Capillaries are small blood vessels that carry oxygen-rich blood to muscle cells, where the oxygen is used for energy production by mitochondria. According to Buckingham, optimal capillary development occurs directly in zone 2, between 60 and 70 percent of your maximum heart rate.

A stronger capillary network allows your body to better utilize more available oxygen during exercise.

3. Long lifespan

Even if you don’t plan on setting a new PR, Zone 2 Cardio can improve your daily life by simply extending it. “Zone 1 and zone 2 exercise has been shown to increase life expectancy,” says Buckingham. “This helps increase VO2 max, and there is a direct relationship between VO2 max and longevity.”

VO2 max is a cardiorespiratory fitness metric that scores how efficiently your body uses oxygen. (Given what we know about capillaries and mitochondria, the link between VO2 Max and Zone 2 cardio makes sense.) This number represents milliliters of oxygen per minute per kilogram of body weight (ml/kg/min).

4. Less need for recovery

There are several reasons why HIIT is popular. It’s fast, efficient, fun (depending on who you talk to), and has many unique benefits. That said, high-intensity exercise requires more recovery than low- or moderate-intensity exercise, and overdoing it can also have negative health effects.

Zone 2 cardio is lower intensity, requiring less recovery time, making it easier to stay consistent with your fitness routine and stay active between workouts. (If you’ve ever been so sore you couldn’t move after a HIIT session, you know.)

Additionally, steady-state aerobic exercise is generally available to a wider range of people, including those new to fitness, those with injuries or mobility impairments, and the elderly.

Zone 2 without aerobic exercise

From a health perspective, most people can benefit from incorporating LISS into their workout routines, but focusing on zone 2 cardio won’t help you achieve your specific performance goals.

If you’re interested in developing explosiveness and power, perhaps you’re a sprinter, high jumper, or baseball player, zone 2 cardio doesn’t have to be your main focus. Instead, you should prioritize short, intense movements.

How often and for how long should I train in Zone 2?

The Centers for Disease Control recommends the following weekly guidelines for aerobic exercise in addition to two days of strength-building exercise.

150 minutes of moderate-intensity activity (also known as Zone 2 cardio)
75 minutes of intense activity
Equivalent combination of moderate and vigorous intensity activities

However, training should be tailored to your goals, fitness level, and lifestyle. For example, an avid runner training for a marathon should log more Zone 2 cardio per week than a time-strapped parent who is just starting out.

You can spread that time out throughout the week (for example, five 30-minute workouts) or throughout the day with exercise “snacks.” For example, jogging for 15 minutes in the morning and riding your bike for 15 minutes after dinner for a total of 30 minutes.

If spending 150 minutes a week on steady-state cardio feels overwhelming, do what you can, Buckingham says.

“Even if you only have 10 or 15 minutes, it’s better than doing nothing. People make the mistake of thinking, ‘I only have 10 minutes to exercise, so it’s not even worth it,'” he says. “Even 10 minutes five days a week is more effective than zero minutes five days a week.”

How to know if you are in Zone 2

You can track your heart rate using a wearable heart rate monitor. But to know when you’re in zone 2, you first need to determine your maximum heart rate. If you don’t have access to a lab or testing facility (and most of us don’t), you can generate a rough estimate using the following formula:

220 – (current age) = maximum heart rate

Therefore, the average 30-year-old person should have a maximum heart rate of 190 and a zone 2 heart rate of 114 to 133 bpm.

However, this formula has been reported to misjudge maximum heart rate by 10 to 12 bpm. It has also been found that young adults overestimate maximum heart rate and older adults underestimate maximum heart rate.

Professor Buckingham therefore recommends conducting your own test on a treadmill or outdoors. “Run as hard as you can for 10 to 15 minutes and give your maximum effort at the end,” he says. Once you reach your peak level of exercise, record your heart rate and use that number to calculate your Zone 2 heart rate.

Alternatively, you can use the “talk test” to keep yourself in Zone 2. “When you’re exercising, you should be able to speak in complete sentences and have full conversations without running out of breath,” says Buckingham. “If you’re gasping for air, you need to slow down.” You need to move at a moderately difficult but sustainable pace and intensity.

Zone 2 aerobic exercise example

Almost any form of exercise is considered Zone 2 cardio, as long as you keep your heart rate within a reasonable range during your workout. Here are some common examples.