What Does “cardio” Actually Mean in the Fitbit App?
Cardio fitness calculation, which was previously only available on the Pixel Watch 3 , is now available on all the latest Fitbit models (and other Pixel Watches) without a Fitbit Premium subscription. So what is it and what exactly does it mean to “hit the target”? I’ll explain.
What is cardio?
Cardio is a way to understand how much exercise you did, whether it was recorded as a workout or not. Longer workouts and exercises at higher intensity increase your cardio load.
So, for example, on a day when you run five miles at an easy pace, you will have a higher cardio load in the Fitbit app than on a day when you run three miles at an easy pace. If you run three miles at a more intense pace (say, a 5K), your cardio load will be somewhere in the middle.
Here are some examples from my training:
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The treadmill workout, in which I alternated between moderate and maximum heart rate zones for an hour (five miles total), had a cardio load of 117 pounds .
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20 minutes of detangling my baby’s hair was recorded as a workout, but since my heart rate was in the easy zone the entire time, I didn’t get any cardio .
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The 53-minute gym workout, which included both heavy lifting and lighter, continuous work, amounted to 63 pounds of cardio .
“Load” here is meant in the sense of “workload”. If you worked out an hour a day this summer and now only do 30 minutes every other day, your cardio load for the week (and for each day) will be lower than it was in the summer. Makes sense, doesn’t it? If you spent the entire next week working out for an hour a day, it would be much higher than your current cardio load, and the Fitbit app would tell you that you’ve suddenly increased your cardio load and might want to take it easy.
What is your target cardio load?
The Fitbit app automatically calculates your cardio target based on what you’re used to doing. You can choose whether you want to improve your fitness (in which case it will push you to do more each week) or maintain your current fitness. You will find this setting when you look at your cardio load. Just click “fitness goal” below.
The actual numbers for your goal will vary from week to week. For example, I was wearing a Fitbit Charge 6 during testing (you’ll learn more about that soon), but I took a break from wearing it for a while. The Fitbit app told me today that it has changed my cardio scale from 0-247 (when I was more active) to 0-191 (which it thinks is more in line with what I should be aiming for now).
I haven’t logged enough action lately to get a more detailed assessment, and I’ll let you guys know when I get the full experience.
What devices have a cardio load?
As of December 2024, cardiovascular devices include:
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Pixel Clocks 1, 2 and 3
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Fitbit Charge 5 and 5
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Fitbit Versa 2, 3 and 4
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Fitbit Sense 1 and 2
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Fitbit Lux
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Fitbit Inspire 2 and 3
In most cases, your cardio activity can be viewed in the Fitbit app (but not necessarily on your device). The Pixel watch can display your cardio activity on the screen.
Other apps and platforms have their own cardio options. For example, some Garmin devices measure training load (along with acute/chronic load and load focus), but it is calculated and displayed slightly differently than Fitbit. This article only discusses the Fitbit/Pixel version.
What is the difference between cardio and active zone minutes?
Both metrics describe how much exercise you do and give you extra credit for heavy exercise compared to moderate exercise. But they have different goals and are calculated slightly differently.
The purpose of Zone Activity Minutes is to see if you’re meeting some basic health exercise goals. The number of minutes of activity in the zone corresponds to US physical activity guidelines, which recommend that we all get 150 minutes of moderate exercise per week or 75 minutes of vigorous exercise. In other words, it’s a minute count, with vigorous exercise (like running) counting double. This is why your 30-minute workout can count as a 45-minute zone if 15 of those minutes were moderate and 15 were vigorous (15 x 2 = 30).
(There’s a caveat: Fitbit uses your heart rate to estimate whether a given minute of exercise was vigorous or moderate for you. The original recommendations used METs, not heart rate , so it’s not a perfect match. But it’s close enough to be useful. )
Cardio fitness, meanwhile, is the metric most often used by athletes to ensure their physical activity is in the optimal range to improve or maintain their fitness. Fitbit uses a modified version of the TRIMP algorithm , which multiplies your heart rate by the number of minutes you spent at that heart rate. If your heart rate is below a certain level, it doesn’t count, so my hair brushing sessions don’t count toward any cardio activity.
With cardio, you’re not just trying to beat the minimum to get a passing grade. You are trying to stay within a certain interval, which is determined by the amount of exercise you are used to doing . If you do a little more exercise each week, you can stay within your target range while pushing the boundaries of that target range. This is how you become better. On the other hand, if you do much more or less exercise this week than your body is used to, you may end up feeling out of shape (if you do less) or more tired than usual (if you do more). Depending on where you are in your training, this isn’t necessarily a bad thing. But by having a cardio goal to compare your workload to, you at least know where you stand.