Buzz
The Cardio Load feature, which was initially exclusive to the Pixel Watch 3, is now available on all recent Fitbit models (as well as the other Pixel Watches) without needing a Fitbit Premium subscription. So, what exactly does it measure, and how do you know when you’ve hit your target? Let’s dive in and explain.
What exactly is cardio load?
Cardio load is a way to assess the amount of physical activity you’ve been doing, regardless of whether it was tracked as an official workout. Longer durations and higher intensity levels during exercise both increase your cardio load.
For example, if you go for a five-mile run at an easy pace, your cardio load in the Fitbit app will be higher compared to a day where you ran three miles at the same pace. However, if you run those three miles at a faster pace—like racing a 5K—your cardio load will fall somewhere between the two.
Here are some workout examples I tracked:
A track workout where I alternated between moderate and peak heart rate zones for an hour (five miles total) resulted in a cardio load of 117.
20 minutes spent detangling my kid's hair was logged as a workout, but since my heart rate stayed in the light zone throughout, I didn’t get any cardio load.
A 53-minute gym session that combined heavy lifts and lighter continuous exercises led to a
cardio load of 63.
The term “load” refers to your “workload.” For instance, if you worked out an hour a day during the summer but now only manage 30 minutes every other day, your cardio load for the week (and daily) will be lower than it was in the summer. Makes sense, right? If next week you were to get back to an hour of exercise every day, your cardio load would increase dramatically, and the Fitbit app would notify you about the jump, suggesting you may want to take it easy.
What’s your target cardio load?
The Fitbit app automatically sets a target cardio load based on your usual activity levels. You can decide whether you want to focus on improving your fitness (in which case it will prompt you to gradually increase your load each week) or maintaining your current level. This setting is accessible when you check your cardio load—just tap on ‘fitness target’ at the bottom.
Your target numbers will fluctuate each week. For example, after using a Fitbit Charge 6 for some testing (more on that soon), I took a break from wearing it. The Fitbit app now shows me that my cardio load range has adjusted from 0-247 (when I was more active) to 0-191, which it thinks is a more suitable target for me at this point.
I haven’t tracked enough activities recently to get a detailed score, but I’ll keep you updated once I get the full experience.
Which devices support cardio load?
As of December 2024, the devices that feature cardio load include:
Pixel Watches 1, 2, and 3
Fitbit Charge 5 and 6
Fitbit Versa 2, 3, and 4
Fitbit Sense 1 and 2
Fitbit Luxe
Fitbit Inspire 2 and 3
Your cardio load can be viewed through the Fitbit app (though not necessarily on the device itself) for most of the devices listed above. Pixel Watches, however, can display your cardio load directly on the screen.
Other platforms and apps have their own versions of cardio load. For example, some Garmin devices track a metric called Training Load (along with acute/chronic load, and load focus), but it’s calculated and presented differently from Fitbit's. This article focuses specifically on the Fitbit/Pixel version.
What’s the difference between cardio load and active zone minutes?
Both metrics track your exercise activity and give extra credit for intense workouts compared to moderate ones. However, they serve different purposes and are calculated in distinct ways.
Active zone minutes are designed to help you track whether you're hitting essential exercise targets for good health. These minutes align with the U.S. Physical Activity Guidelines, which suggest that everyone should aim for 150 minutes of moderate activity weekly or 75 minutes of vigorous activity. Essentially, it’s a tally of minutes, with vigorous activities (like running) counting double. So, for instance, if you engage in a 30-minute workout where 15 minutes are moderate and 15 are vigorous (15 x 2 = 30), you’ll earn 45 zone minutes.
A small note: Fitbit estimates whether a minute of exercise was moderate or vigorous based on your heart rate. The original guidelines, however, used METs (metabolic equivalents) rather than heart rate, meaning it’s not a flawless match, though it is sufficiently close for practical use.
Cardio load is a metric frequently used by athletes to ensure their exercise intensity stays within an optimal range for fitness improvement or maintenance. Fitbit adapts a version of the TRIMP algorithm, which multiplies your heart rate by the duration of time spent at that intensity. If your heart rate is too low, it doesn't count toward your cardio load, which is why everyday activities like brushing your hair won’t impact your load measurement.
With cardio load, the goal is more than just meeting a minimum; it’s about staying within a specific range that corresponds to your usual exercise level. By gradually increasing your weekly activity, you can stay within this target range while also expanding the boundaries of that range. That’s how you improve your fitness. However, if your activity levels are much higher or lower than what your body is accustomed to, you might risk losing fitness (if doing less) or overexerting yourself (if doing more). These outcomes aren’t always negative, depending on where you are in your fitness journey, but having a cardio target gives you clarity on where you stand.
