What ‘Zone 2’ Cardio Actually Means

“Zone 2” is the term that the fitness world has (mostly) accepted to describe the low-intensity cardio that most of us should be doing regularly. When you’re in zone 2, you’re working hard enough that you start breathing harder, but easy enough that you can hold a conversation while doing it. You stop a session in zone 2 because your training time is up, not because you are too exhausted to continue. Zone 2 is defined in terms of heart rate, so what heart rate should you expect to see on your watch when you’re in zone 2? This is where people disagree.

What is zone 2 training?

As I’ve already explained, the name “zone 2” comes from heart rate training. To train by heart rate, you either use a wristwatch with an optical heart rate sensor (that green light on the back), or a chest strap paired to your watch or just a phone (chest straps are more accurate, and even a $30 belt can do a great job).

To train by heart rate, your goal is to keep your heart rate in the “zone” that gives you the workout you want. In most popular systems, there are five zones. Zone 1 is your rest or recovery zone; zone 2 is low intensity cardio; zone 3 is more or less average; and zones 4 and 5 are for more intense efforts, usually done for just a few minutes, with recoveries in zone 1 or 2 in between. (I have a more detailed guide to the zone system here.) Although Zone 2 is the hottest right now, the other zones still have uses. Personally, I think zone 3 is underrated, and most of us would probably be better off having a mix of zones 2 and 3 for our regular cardio rather than pure zone 2. But that’s a story for another time.

Heart rate zones are usually defined as percentages of your maximum heart rate. So when I set my Apple Watch to keep me in Zone 2 during my runs, it wants my heart rate to be between 60% and 70% of maximum. Even with easy effort, I found that I usually exceeded this limit. In contrast, when I ride a Peloton bike, my heart rate is often still in zone 1 when I could swear I’m riding at zone 2 effort. Turns out Peloton defines zone 2 as 65% to 75% of my max.

Who is right? Well, everyone. “Zone 2” is not a term with scientifically designed boundaries. Anyone can divide heart rate zones however they want. (Stay tuned for my patented eight-zone system, as soon as I find a way to monetize it!) If you train with more than one gadget, or if you’re discussing heart rate training with a friend who uses a different system than you, it’s worth knowing the differences.

What percentage of heart rate counts as zone 2?

Let’s take a look at some of the most popular wearables and fitness systems that measure heart rate in a five-zone system, or something like that.

First, it’s important to know that most (not all) of these percentages are based on your maximum heart rate. To know your maximum heart rate, you need real numbers and you shouldn’t rely on the default values ​​provided by your app. This default number is derived from a formula, and no formula will be exact for everyone; Maximum heart rate varies from person to person and cannot be accurately predicted for individuals. You can do a field test, like increasing your heart rate by doing increasingly intense hill reps. Or if you have a lot of experience doing intense exercise, simply write down the highest heart rate number you’ve seen on your device; it will probably be close to your maximum.

Most zone systems simply use a percentage of your maximum (however that maximum is calculated). There are also other systems to consider. “Heart rate reserve” (HRR) means that you take the difference between your maximum heart rate and your resting heart rate (instead of between your maximum heart rate and zero) and calculate from there. Some devices will estimate a different benchmark, like your lactate threshold, and use that as the basis for zones.

So here are the Zone 2 percentages of a variety of popular wearables, along with their percentages. of:

• Apple Watch: Zone 2 represents 60-70% of your heart rate reserve, with your “resting” heart rate set to 72 or a number the watch has picked up automatically, and your maximum is calculated with the 220 age formula. (You can choose to set zones manually instead.)

• Fitbit and Pixel: Instead of “Zone 2,” Fitbit devices have a “Moderate” zone (formerly called “fat burn”) set between 40% and 59% of your heart rate reserve. To know your heart rate reserve, your max is calculated using the 220-year formula, and your resting heart rate is measured by the device. You can set your maximum and zones manually if you prefer.

• Garmin: Depends on your device and how you have chosen to configure your zones. As a percentage of maximum heart rate, zone 2 is between 73 and 81%. As a percentage of heart rate reserve, it is 65 to 75%. And as a percentage of your lactate threshold heart rate (which the watch can automatically detect for you and which is normally between zones 4 and 5), that’s 79-88% of that heart rate. Note that these numbers do not necessarily correspond to each other. A heart rate that is in zone 2 on one of these systems may be in zone 3 on another. And of course, you can set your maximum and/or zones manually.

Some other fitness platforms have set heart rate zones to use with your workout. To name just a few:

• Orange Theory gets its name from the “orange” zone it wants you to be in during workouts. Its equivalent of zone 2 would be the “blue” zone, at 61% to 70% of maximum heart rate. It uses an “industry standard formula” to determine your maximum, which Self says is 208 minus 0.7 times your age. After completing 20 classes, an algorithm will select a new maximum heart rate for you.

• Platoon defines heart rate zone 2 (unrelated to power zone 2) as 65% to 75% of your maximum heart rate. Maximum heart rate is 220 minus your age unless you adjust it manually in your settings.

• THE American College of Sports Medicine defines “light” training, arguably its version of zone 2, as 57% to 63% of maximum heart rate. “Moderate” is 64% to 76%.

How do you know which benchmark to use?

Rather than obsessing over the numbers, think about the bigger picture and decide what ripple effect you’re trying to achieve with your workouts. If you want to build endurance with low-intensity cardio, or if you want to accumulate minutes in zone 2 to help you lose weight, it doesn’t matter exactly what your heart rate is. What matters is that you can do the exercise for a long time without getting tired, but that you also don’t slack off and do almost no work.

In other words, you can use your gadget’s heart rate numbers as a guide, but keep it honest with a reality check based on what fitness pros call “perceived exertion.” If you want to focus on a number, you can rate your effort on a scale of 1 to 10 – called RPE for “rating of perceived exertion” – and aim for an RPE of around 3 to 4.

Over time, you’ll start to notice what heart rate tends to show on your watch when you’re at this level. I know that if my heart rate is below 150, I’m doing a good job of keeping my jogging in a sort of “zone 2” effort. If he hits 160 at the start of a run, that’s probably harder than I want, but if he hits 160 at the end of a long run on a hot day, that’s no problem. (Heart rate changes with temperature and the duration of your workout, a phenomenon called cardiac drift.) These numbers are just examples, and my maximum is quite high for my age, close to 200. Yours will be different.

Ultimately, this is probably the most accurate way to use heart rate to determine exercise intensity: first determine your desired intensity and use heart rate as a guide so you can achieve that same intensity consistently. After all, if there was a correct, easy-to-determine number, different gadgets and platforms would all have it built in by now. So trust your body more than your watch.