No One Can Agree on What “zone 2” Cardio Is.

“Zone 2” is the name the fitness world has (mostly) agreed upon to describe the low-intensity cardio that most of us should be doing . When you’re in zone 2, you’re working hard enough to start breathing harder, but light enough to keep the conversation going. You stop training in zone 2 because the training time is up, not because you are too tired to continue. But what heart rate should you see on your watch when you’re in zone 2? This is where we humans disagree.

As we explained earlier, the name “zone 2” comes from training with heart rate. In most popular systems, there are five zones. Zone 1 is your rest or recovery area; zone 2 – low-intensity cardio; and zones 3, 4 and 5 are for heavier efforts. (We have a guide to the zone system here .)

Zones are usually defined as a percentage of your maximum heart rate. So when I set my Apple Watch to stay in zone 2 during runs, they want my heart rate to be between 60% and 70% of my max. Even with a light effort, I found myself usually exceeding this limit. On the other hand, when I sit on a Peloton bike, my heart rate is often still in zone 1, even though I can swear I’m riding zone 2 with effort. It turns out that the system detects zone 2 as 65-75% of my maximum.

Who is right? Well, everything. “Zone 2” is not a term with a scientific definition. Everyone can divide the heart rate zones as they see fit. (Keep an eye out for my proprietary eight-zone system, which will be out as soon as I find a way to monetize it!) systems than you, it’s worth knowing the differences.

What percentage of heart rate is considered zone 2?

Let’s take a look at some of the more 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 find out your maximum heart rate, you need to do a real test, not just calculate it with a formula. For example, one formula calculates my maximum heart rate as 178 beats per minute, while another says it should be 169; in fact, I’ve seen up to 207 when running and 198 on a spinbike. (And yes, your maximum may vary for different types of cardio. My heart rate during swimming will probably be even lower; when your body is in a horizontal position, it is easier for your heart to move blood.)

There are other systems to consider as well. “Heart rate reserve” (HRR) means you take the difference between your max and your resting heart rate (rather than between your max and zero) and calculate from that. Some gadgets estimate another benchmark, such as lactate threshold, and use that as the basis for zones.

So, here are the Zone 2 percentages of various popular wearables, along with their percentages :

• Apple Watch : Zone 2 is 60-70% of your heart rate reserve, with your resting heart rate set to either 72 or the number the watch picks up automatically, and your maximum is calculated using the 220-age formula . (You can set zones manually instead.)
• Garmin : Depends on the model. Some set zone 2 to 60-70% of your maximum or heart rate, but other devices will measure your lactate threshold and set the zone to 80-89% of your threshold heart rate. You can also set zones manually, and some models allow you to set different heart rate zones for different sports, such as swimming, cycling, and running.
• Fitbit : Instead of “zone 2”, Fitbit devices have a “fat burn” zone, which they define as 50% to 69% of your maximum heart rate on some devices and 40% to 69% of your heart rate on others. In either case, your maximum is calculated using the 220-age formula. You can set your maximum and your zones manually if you like.

Some other fitness platforms define heart rate zones for use during workouts. To name a few:

• Orangetheory gets its name from the “orange” zone they want you to be in while exercising. Their zone 2 equivalent would be the “blue” zone, with a heart rate between 61% and 70% of maximum. They use an “industry standard formula” to determine your maximum, which Self says is 208 minus 0.7 your age. After you complete 20 sessions, the algorithm will determine a new maximum heart rate for you .
• Peloton defines heart rate zone 2 (not related to power zone 2) as 65% to 75% of your maximum heart rate. The maximum heart rate is 220 unless you manually adjust it in settings.
• The American College of Sports Medicine defines a “light” workout, perhaps their version of zone 2, as 57-63% of your maximum heart rate. “Moderate” – from 64% to 76%.

How do you know which benchmark to use?

Instead of getting hung up on numbers, think about the big picture and decide what kind of training effect you are trying to achieve through training.

Whether you’re looking to increase your endurance with low-intensity cardio, or if you’re looking to get a few minutes into this zone to help you lose weight, it doesn’t matter what your heart rate is. The important thing is that you can do the exercise for a long time without tiring, but at the same time you do not swing so much that you do almost no work.

In other words, you can use your gadget’s heart rate readings as a guide, but keep it fair with a reality check based on what fitness experts call “perceived exertion.” If you need a number to pay attention to, you can rate your load on a scale of 1 to 10 (called RPE for “perceived load rating”) and aim for an RPE of around 3 to 4.

Over time, you will begin to notice how your heart rate usually appears on your watch when you are at this level. I know that if my heart rate is in the 140 to 150 range, I’m doing well with my “zone 2” run. If it goes up to 160 at the start of a run, that’s probably harder than I’m going for, but if it hits 160 at the end of a long run on a hot day, that’s fine (Heart rate varies with temperature and the length of your workout, a phenomenon called cardiac drift .)

Ultimately, this is probably the most accurate way to use heart rate to determine exercise intensity: First determine the intensity you want and use heart rate as a guide so you can maintain the same intensity consistently. After all, if there was one correct number that was easy to determine, all gadgets and platforms would already be familiar with it by this point. So trust your body more than your watch.