What does ‘Zone 2’ cardio really mean?

“Zone 2” is the term the fitness world has (mostly) agreed upon to describe the lower intensity cardio that most of us should be doing on a regular basis. When you’re in Zone 2, you’re working so hard that you start breathing more heavily, but easy enough that you can hold a conversation while doing so. You stop a Zone 2 session because your workout time is up, not because you’re too tired 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 mentioned earlier, the name “Zone 2” comes from heart rate training. To train based on heart rate, you either use a wrist watch with an optical heart rate sensor (that’s the green light on the back) or a chest strap paired with your watch or just a phone (chest straps are more accurate, and even a $30 watch can do an excellent job).

To train by heart rate, your goal is to keep your heart rate in the “zone” that gives you your desired workout. 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 moderate; And Zones 4 and 5 are for harder efforts, usually done for only a few minutes with recovery in Zones 1 or 2 in between. (I have a more detailed guide to the zone system here.) While Zone 2 is the trendiest at the moment, there are still uses in other zones. Personally, I think zone 3 is underrated, and probably most of us would be better off having a mix of zones 2 and 3 rather than pure zone 2 for our steady cardio. But that’s a story for another time.

Heart rate zones are usually defined as a percentage of your maximum heart rate. So when I set my Apple Watch to put me in Zone 2 while I run, it wants my heart rate to be between 60% to 70% of maximum. Even with an easy effort, I found I was usually exceeding that limit. On the other hand, when I hop on a Peloton bike, my heart rate is often in Zone 1, while I could swear I’m riding at a Zone 2 effort. It turns out that Peloton defines Zone 2 as 65% to 75% of my max.

who is right? Okay, everyone. “Zone 2” is not a term with scientifically designed boundaries. One can divide the heart rate zones as per one’s wishes. (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 find yourself discussing heart rate training with a friend who uses a different system than you, it’s worth knowing the differences.

What heart rate percentage is counted as zone 2?

Let’s take a tour of some of the more popular wearable devices and fitness systems that measure heart rate in a five-zone system or something similar.

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-world numbers, and you shouldn’t rely on the defaults given by your app. That default number is derived from a formula, and no one formula will be accurate for everyone; Maximum heart rate varies from person to person and cannot be predicted accurately for each person. You can do a field test, such as increasing your heart rate by running more and more intense hill repeats. Or if you have plenty of experience with intense exercise, simply note the highest heart rate number you see on your device; This will probably be close to your maximum limit.

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

So, here are the Area 2 percentiles of a variety of popular wearables, along with what those percentiles are. Of: :

• apple watch: Zone 2 is 60-70% of your heart rate reserve, with your “resting” heart rate set to either 72 or a number automatically picked by the watch, and your max calculated with the 220-for-age formula. (You can choose to set the zone manually instead.)

• fitbit and pixel: Instead of “Zone 2”, Fitbit devices have a “medium” zone (formerly called “fat burn”) set at 40% to 59% of your heart rate reserve. To find your heart rate reserve, your maximum is calculated according to the 220-age formula, and your resting heart rate is measured by the device. You can set your maximum and your area manually if you want.

• garmin: This depends on your device and how you chose to set up your zone. As a percentage of maximum heart rate, zone 2 is 73–81%. As a percentage of heart rate reserve, it is 65–75%. And as a percentage of your lactate threshold heart rate (which the watch can automatically detect for you, and which normally falls between zones 4 and 5), it’s 79-88% of that heart rate. Note that these numbers will 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 the other system. And, of course, you can set your max and/or your zone manually.

Some other fitness platforms have defined heart rate zones to use in your training. to name a few:

• orangetheory Its name is derived from the “orange” zone it wants you to be in during a workout. The 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 limit, which is itself reports 208 minus 0.7 times your age. After you take 20 classes, an algorithm will select a new maximum heart rate for you.

• peloton defines Heart rate zone 2 (no relation to power zone 2) 65% to 75% of your maximum heart rate. The maximum heart rate is 220 minus your age, unless you adjust it manually in your settings.

• American College of Sports Medicine defines “Light” training, probably its version of Zone 2, 57% to 63% of maximum heart rate. “Moderate” is 64% to 76%.

How do you know which benchmark to use?

Instead of focusing on the numbers, think about the bigger picture and decide what training effect you’re trying to achieve with your workout. If you want to increase your endurance with low-intensity cardio, or if you want to spend minutes in Zone 2 to help with weight loss, it doesn’t matter what your heart rate is. What matters is that you can exercise for a long time without getting tired, but at the same time you are not slacking off and barely getting any work done.

In other words, you can use your gadget’s heart rate numbers as a guide, but keep them honest with reality checks based on “perceived exertion” by fitness professionals. If you want to focus on a number, you can rate your exertion 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 see what heart rate appears on your watch when you’re at that level. I know that if my heart rate is under 150, I’m doing a good job of keeping my jogging like “Zone 2.” If it gets to 160 at the start of a race, it’s probably harder than I anticipated – but if it gets to 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 heart flow.) These numbers are just examples, and my maximum number is quite high for my age, closer to 200. Your numbers will be different.

Ultimately, this is probably the most accurate way to use heart rate to determine exercise intensity: first figure out the intensity you want, and use heart rate as a guide to be able to achieve the same intensity on a consistent basis. After all, if there was an exact number that was easy to determine, various gadgets and platforms would have integrated with it by now. So trust your body more than your watch.