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The cardio load calculation, so far only on on the Pixel Watch 3is now available for all current Fitbit models (and the other Pixel watches) without a Fitbit Premium subscription. So what is it and what exactly does achieving your goal mean? I’ll explain.
What is cardio load?
Cardio Load helps you understand how much exercise you’ve done, whether it’s logged as exercise or not. Longer workouts and higher intensity workouts increase your cardio load.
For example, on a day when you run five miles at an easy pace, the Fitbit app will show a higher cardio effort than on a day when you ran three miles at an easy pace. If you run three miles at a more intense pace – say you’re running a 5K – your cardio load will be somewhere in between.
Here are a few examples of some of the workouts I did:
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A running workout where I alternated between medium and maximum heart rate zones for an hour (five miles total) had one Cardio load of 117.
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Detangling my child’s hair for 20 minutes was logged as exercise, but since my heart rate was in the light range the entire time, I didn’t get any cardio load.
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A 53-minute gym workout, which included a mix of heavy lifting and lighter sustained work, lasted 10 minutes Cardio load of 63.
“Load” is to be understood here in the sense of “workload”. If you exercised for an hour a day this summer and are currently only exercising for 30 minutes every other day, your cardio load for the week (and for each day) will be less than it was in the summer. Makes sense, right? If you exercised for an hour a day for the next week, that would be much more than your current cardio load – and the Fitbit app would let you know that you’ve suddenly increased your cardio load and might want to relax a bit.
What is your target cardio load?
The Fitbit app automatically calculates a target cardio load based on your habits. You can choose whether you want to improve your fitness (in this case you will be encouraged to increase your workload a little higher each week) or maintain your current fitness. You can find this setting by looking at your cardio load. Simply tap “Fitness Goal” below.
The actual numbers of your goal change from week to week. For example, I wore a Fitbit Charge 6 for some testing (more on that soon), but took a break from wearing it for a while. The Fitbit app tells me today that it adjusted my cardio effort scale from 0-247 (when I was more active) to 0-191 (which I think is more in line with what I should be aiming for now).
I haven’t logged enough activity recently to provide a more detailed review, and I’ll update you once I have the full experience.
Which devices have cardio load?
As of December 2024the devices that have cardio load are:
For most of the above, your cardio effort is visible in the Fitbit app (but not necessarily on your device). The Pixel watches can show you your cardio load on the screen.
Other apps and platforms have their own versions of Cardio Load. For example, some Garmin devices measure training load (along with acute/chronic load and load center), but this is calculated and displayed slightly differently than Fitbit’s. This article is only about the Fitbit/Pixel version.
What is the difference between cardio load and active zone minutes?
Both metrics describe how much exercise you complete, giving you additional credit for hard training compared to moderate training. But they have different purposes and are calculated slightly differently.
The purpose of Active Zone Minutes is to find out if you are meeting some basic exercise goals for your health. Active Zone Minutes are consistent with the US Physical Activity Guidelines, which recommend this We all do 150 minutes of moderate exercise per weekor 75 minutes of intense exercise. In other words, it’s a count of minutes, with intense exercise (like running) counting double. For this reason, your 30-minute workout could include 45 zone minutes if 15 of those minutes were moderate and 15 minutes were vigorous (15 x 2 = 30).
(There’s a caveat here: Fitbit uses your heart rate to estimate whether a given minute of exercise was strenuous or moderate for you. The The original guidelines used METs, not heart rateso it’s not a perfect match. But it’s close enough to be useful.)
Cardio load, on the other hand, is a metric more commonly used by athletes to ensure that their training effort is within the optimal range to improve or maintain their fitness. Fitbit uses a modified version of this TRIMP algorithmwhich basically 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 won’t count, which is why my hairbrushing sessions didn’t count toward cardio.
When it comes to cardio, it’s not just about achieving a minimum level in order to get a passing grade. They try to stay within a specific window defined by the amount of exercise you are used to. Exercising a little more each week will help you stay within your goal range while pushing the boundaries of that goal range. This is how you get fitter. On the other hand, if you exercise a lot more or a lot less this week than your body is used to, you could end up losing some fitness (if you do less) or feeling more tired than usual (if you do more). Depending on where you are in your education, these aren’t necessarily a bad thing. But with a cardio goal to compare your effort against, you’ll at least know where you stand.
