No One Can Agree on What “zone 2” Cardio Is.
This post is part of Find Your Fit Tech , a fitness wearable buying guide from Lifehacker. I ask tough questions about whether wearables can really improve your health, how to find the one that’s right for you, and how to make the most of the data wearables have to offer.
“Zone 2” is a term that’s (mostly) accepted in the fitness world to describe the low-intensity cardio workouts that most of us should be doing regularly . When you’re in zone 2, you’re working hard enough that you’re breathing heavier, but light enough that you can still carry on a conversation. 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 expect on your fitness smartwatch when you’re in zone 2? This is where people disagree.
What is Zone 2 training?
As I explained earlier , the name “zone 2” comes from heart rate training. Most popular systems have 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. (I have a guide to the zone system here .)
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 runs, it wants my heart rate to be between 60% and 70% of my maximum. Even with light efforts, I find that I usually exceed this limit. On the other hand, when I get on a Peloton bike, my heart rate is often still in zone 1, even though I could swear I’m riding hard in zone 2. It turns out that the system detects zone 2 as 65-75% of my maximum.
Who is right? Well, that’s it. “Zone 2” is a term that has no scientific definition. Anyone can divide heart rate zones as they wish. (Keep an eye out for my proprietary eight-zone system, coming as soon as I figure out a way to monetize it!) If you’re training with more than one gadget, or 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 is considered zone 2?
Let’s take a tour of some of the more popular wearables and fitness systems that measure your 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 and not just calculate it using a formula. For example, according to one formula my maximum heart rate is 178 beats per minute, and according to another it is 169; in fact, I’ve seen up to 207 when running and up to 198 on the stationary bike. (And yes, your max may vary between different types of cardio. My heart rate while swimming would likely be even lower; when your body is horizontal, it’s easier for your heart to move blood.)
There are other systems to consider. Heart rate reserve (HRR) means that you take the difference between your maximum heart rate and your resting heart rate (not between your maximum and zero) and calculate from there. Some gadgets evaluate another indicator, such as lactate threshold, and use this as a basis for zones.
So, here are the Zone 2 percentages from various popular wearables, as well as their percentages :
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Apple Watch : Zone 2 is 60-70% of your heart rate reserve, with your resting heart rate set to 72 or the number the watch automatically finds, and the maximum calculated using the 220 age formula. (You can set zones manually instead.)
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Garmin : Depends on model. Some set Zone 2 to 60-70% of your maximum or heart rate, but other devices 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.
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Fitbit : Instead of a “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 any case, your maximum is calculated using the age formula of 220 years. If you want, you can set your maximum and zones manually.
Some other fitness platforms have specific heart rate zones that you can use during your workouts. To name a few:
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Orangetheory gets its name from the “orange” zone you are supposed to be in during your workouts. Their equivalent to zone 2 would be the “blue” zone at 61% to 70% of your maximum heart rate. They use an “industry standard formula” to determine your maximum, which Self says is 208 minus 0.7 of your age. After you complete 20 classes, the algorithm will select a new maximum heart rate for you .
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Peloton defines heart rate zone 2 (not associated with power zone 2) as 65% to 75% of your maximum heart rate. The maximum heart rate is 220 ages unless you adjust it manually in the settings.
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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 test to use?
Instead of focusing on the numbers, think about the big picture and decide what training effect you are trying to achieve with your training.
Whether you’re looking to improve your endurance with low-intensity cardio or want to spend a few minutes in 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 getting tired, but you’re not being buffeted around so much by the sandbags that you’re doing little to no work at all.
In other words, you can use your gadget’s heart rate readings as a guide, but be honest with them by doing a reality check based on what fitness professionals 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, which stands for rating of perceived exertion, and aim for an RPE value of about 3 to 4.
Over time, you will begin to notice what your heart rate typically shows on your watch when you are at this level. I know that if my heart rate is between 140 and 150, I’m doing a good job of keeping my running at a “zone 2” type of effort. If it hits 160 at the start of a run, it’s probably harder than I intend, but if it hits 160 at the end of a long run on a hot day, that’s normal (heart rate changes depending on temperature and length of workout – a phenomenon called cardiac drift ). )
Ultimately, this is probably the most accurate way to use heart rate to determine exercise intensity: first determine your desired intensity and use your heart rate as a guide so you can maintain the same intensity on a consistent basis. After all, if there was one correct number that was easy to define, all the different gadgets and platforms would already agree on it. So trust your body more than your watch.