Zone 2 cardio puts the “steady” in “steady-state cardio.” It’s not flashy like high-intensity interval training (HIIT) or dramatic like bonking, yet it deserves just as much attention.
Zone 2 cardio is foundational to any fitness routine, whether you’re an endurance athlete who wants to improve their performance or someone who just wants to be a healthy, functional human.
So, if you’ve noticed a “trend” around this type of exercise, know this: Low-intensity, steady-state cardio (LISS cardio) has always been around. And if, until now, it hasn’t been part of your exercise routine, it’s time to change that.
What Is Zone 2 Cardio?
Zone 2 cardio refers to a specific exercise intensity that you can sustain for an extended period, during which your heart rate is about 60 to 70 percent of your max heart rate. (Your max heart rate is the number of times your heart beats in a minute during an all-out effort, like sprinting the final stretch of a 5K. More on how to determine your max heart rate later.) In this zone, you may be slightly breathy, but you’re not gasping for air.
There are five heart rate zones, each of which has a target range based on a percentage of your max heart rate (MHR). Below is a general breakdown of heart rate zones, but note that these numbers are estimates and may differ according to your source and from one person to the next.
| Zone | Intensity | % of MHR |
|---|---|---|
| Zone 1 | Low–moderate | 50%–60% |
| Zone 2 | Moderate | 60%–70% |
| Zone 3 | Moderate–high | 70%–80% |
| Zone 4 | High | 80%–90% |
| Zone 5 | Very high | 90%–100% |
Zone 2 Cardio Benefits
Like any form of cardio exercise, zone 2 cardio can bolster heart health and reduce the risk of cardiovascular disease. And because it burns calories, steady-state cardio is an effective tool for weight loss and healthy weight management. Zone 2 cardio (and movement, in general) can also positively impact your mood and mental health and improve the quality of your sleep.
But cardio that specifically keeps your heart within the zone 2 range also offers some unique benefits, especially for endurance athletes who want to improve their performance. Here are a few:
1. More mitochondria
If it’s been a while since you took a biology class, here’s a quick refresher on what mitochondria are and why they’re critical to athletic performance:
Mitochondria are a type of organelle found in the body’s cells that use oxygen to produce adenosine triphosphate (ATP), the primary source of energy that fuels physical activity as well as basic biological functions. More mitochondria means more ATP and, therefore, more energy for physical activity.
Todd Buckingham, Ph.D. Exercise Physiologist at PTSportsPRO in Grand Rapids, Michigan, explains that zone 2 cardio is “ideal for mitochondria development.” Working out at a sustainable intensity for a longer duration increases your cells’ demand for energy, and the body adapts to this demand by producing more mitochondria.
So, for athletes who want to up their endurance (or just feel better during and after a workout), zone 2 cardio is essential.
2. Capillary development
Capillaries are small blood vessels that deliver oxygen-rich blood to the muscle cells, where the oxygen is used to manufacture energy by the mitochondria. According to Buckingham, optimal capillary development occurs squarely in zone 2, between 60 and 70 percent of your max heart rate.
A more robust network of capillaries allows your body to put more available oxygen to good use during exercise.
3. Longevity
Even if you’re not looking to set any new PRs, zone 2 cardio can enhance your everyday life by simply extending it. “Zone 1 and zone 2 exercise has been shown to increase life expectancy,” Buckingham says. “It helps increase your VO2 max, and there’s a direct relationship between your VO2 max and your longevity.”
VO2 max is a cardiorespiratory fitness metric that scores how efficiently your body uses oxygen. (The link between VO2 Max and zone 2 cardio makes sense, considering what we know about capillaries and mitochondria.) The number measures milliliters of oxygen per kilogram of body weight per minute (ml/kg/min).
4. Requires less recovery
HIIT is popular for multiple reasons: It’s fast, efficient, fun (depending on who you talk to), and offers plenty of its own unique benefits. That said, high-intensity exercise requires more recovery than low or moderate-intensity exercise, and doing too much of it can even negatively impact your health.
Because it’s less intense, zone 2 cardio requires less recovery time, which makes it easier to remain consistent with your fitness routine and stay active between workouts. (If you’ve ever been too sore to function after a HIIT session, you get it.)
Additionally, steady-state cardio is generally accessible to more people, including those new to fitness, individuals with injuries or mobility issues, and older adults.
When Not to Use Zone 2 Cardio
While almost anyone will, from a health perspective, benefit from incorporating LISS into their workout routine, focusing on zone 2 cardio won’t help you achieve certain performance goals.
If you’re concerned with developing explosiveness and power — maybe you’re a sprinter, a high jumper, or a baseball player — zone 2 cardio should not be your primary focus. Instead, you should prioritize short bouts of intense movement.
How Often and Long Do You Need to Train in Zone 2?
Along with two days of muscle-strengthening exercise, the Centers for Disease Control recommends the following weekly guidelines for aerobic activity:
- 150 minutes of moderate-intensity activity (a.k.a. zone 2 cardio)
- 75 minutes of vigorous-intensity activity
- An equivalent combination of moderate- and vigorous-intensity activity
However, your training should align with your goals, fitness level, and lifestyle. For example, an avid runner training for a marathon needs to log more zone 2 cardio per week than a time-pressed parent who’s just beginning to exercise for the first time.
That time can be distributed throughout the week (e.g., five 30-minute workouts) and even throughout the day with exercise “snacks.” For example, you could do a 15-minute jog in the morning and a 15-minute bike ride after dinner for a total of 30 minutes.
If 150 minutes a week feels like an overwhelming amount of steady-state cardio, do what you can, Buckingham says.
“If you only have time for 10 or 15 minutes, that’s still going to be better than nothing. People make the mistake of going, ‘I only have time for 10 minutes of exercise, so it’s not even worth it,’” he says. “Even 10 minutes five days a week is going to be better than zero minutes five days a week.”
How to Know When You’re in Zone 2
You can use a wearable heart rate monitor to track your heart rate. But in order to know when you’re in zone 2, you must first determine your max heart rate. If you don’t have access to a lab or testing facility (and most of us don’t), you can use this formula to generate a rough estimate:
220 – [current age] = max heart rate
So, the average 30-year-old person should have a max heart rate of 190, and their zone 2 heart rate should be between 114 and 133 bpm.
However, this equation has been reported to misjudge max heart rate by 10 to 12 bpm. It has also been found to over- and underestimate max heart rate in younger and older adults, respectively.
Thus, Buckingham recommends conducting your own test on a treadmill or outside. “Run as hard as you can for 10 to 15 minutes, maxing out at the end,” he says. When you’re at your peak level of exertion, note 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 hold a full conversation, speaking in complete sentences without becoming out of breath,” Buckingham says. “If you’re gasping for air, you need to slow down.” You should be moving at a pace and intensity that feels moderately challenging but sustainable.
Zone 2 Cardio Examples
Almost any form of exercise can be considered zone 2 cardio if you keep your heart rate within the appropriate range for the duration of your workout. Here are some common examples:
- Brisk walking
- Jogging
- Running
- Hiking
- Swimming
- Dancing
- Aerobics
- Cycling
- Rowing
- Elliptical training
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