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Active Zone Minutes represent a new holy grail of sorts for those who believe in the science and tech behind Fitbit’s basic health and exercise concepts.
They’re joined at the hip to the company’s heart zone training, and they’ve replaced Active Minutes, the predecessor that was the linchpin of the Fitbit Charge 4. Instead, they’re designed to add precise numerical benchmarks to your exercise program, at least as it pertains to movement and your heart rate.
Of course, it’s all very ambitious, which means there’s a lot to dig into. Some of what Fitbit is up to with Active Zone Minutes is based on legit science, while other parts of it may be questionable, so let’s pull back the curtain and see if we can figure out what zone minutes are on Fitbit and how they work.
How Active Zone Minutes Work
This is the starting line, of course, and the basic numerical concept behind Active Zone Minutes is straightforward. It’s actually based on a one-to-one correspondence-if you elevate your heart rate into the fat burn zone, one minute in that zone gets you credit for one minute toward your goal.
If you push harder and enter the Cardio or Peak heart rate zones, the number of points you get doubles, and you get two minutes.
The goal is to give you alerts while you’re exercising so you know where you are about heart zone training, and you can add your numbers and keep track of your score.
According to Fitbit, it takes the guesswork and the overt math out of this kind of training-and. After all, who among us other than accountants, mathematicians, and other bean-counter types, likes to do math?
In addition to the “extra precision” marketing angle, part of the idea here is to show that Fitbit is relentlessly moving forward in its efforts to advance its exercise metrics into a more precise future.
Active Minutes vs. Active Zone Minutes
Now that we’ve covered the basic concept, let’s take a deeper dive into the before vs. after part of this. To wit-how did Active Minutes work, and how do Active Zone Minutes work?
Not surprisingly, Time is the most significant difference. With Active Minutes, you had to be moving for ten minutes before you could start getting credit.
Meanwhile, credit for Active Zone Minutes comes immediately, so you can get credit for what we’ll call “here and there” minutes, e.g., the minutes you might spend running up and down some stairs for a few minutes.
If you push hard enough to get into the fat-burning zone when you’re doing those kinds of activities, you’ll get that doubling effect, and you’ll get credit for more active zone minutes.
Doing the Math
So what’s the breakdown for all this when comparing Active Zone Minutes (AZM) vs. Active Minutes (AM)? One of the first things people notice about AZM is that they may not be getting the same credit for these minutes they did for AZ minutes.
To break it down, we have to take a brief foray into the dreaded “math zone” and examine the basis for how these measurements and numbers are calculated.
AZM is calculated based on the time spent in each heart rate zone, which is different for everyone. Fitbit’s algorithm for this particular number is based on the Karvonen calculation, familiar to many fitness buffs. First, it uses the number 220 minus your age to give you your HF Max. From there, your resting heart rate is subtracted from the HR Max number to give you what Fitbit calls your heart rate reserve.
To get into different heart rate zones, the calculation will be based on your resting heart rate plus 40 percent x the heart rate reserve to get into fat-burning mode. That number jumps to 60 percent for the Cardio zone, and for Peak, it jumps again to 85 percent.
Moreover, as you get fitter, your body theoretically gets more efficient at all this, which means you’ll likely have to do more to trigger AZM minutes.
With AZM minutes, the critical number to soot for is 150 minutes a week. This is based on guidelines from the World Health Organization (WHO) and the American Heart Association (AHA), which recommend either 150 minutes of basic exercise or 75 minutes of vigorous exercise per week.
With the Fitbit Charge 4, that number is displayed as 22 minutes per day, but there is some flexibility there. For example, you can shoot for a daily or a weekly goal, depending on how you structure your workout programs, e.g., when you want to push hard vs. when you want to take more leisurely days.
The procedure to change all this is both easy and simple. The dashboard on the Fitbit app has an AZM icon that allows you to see your progress, and you can change what you see from daily to weekly and back. You can also tap the tog icon and type in your daily and weekly AZM targets.
What Devices Will Have AZM?
Given all the changes, it’s important to know which devices will implement AZM minutes. They debut on the Charge 4, and the company is rolling it out on its smartwatches soon, which means the Versa and the Ionic are expected to be included.
If you’re expecting it to come to the Inspire HR, though, don’t wait too long. Because it’s not happening there, so there’s a phase-out of sorts taking place in that particular device.
Science vs. Skepticism
So what’s the final verdict on all this? First, the heart rate numbers make basic sense-they’ve been used by exercise physiologists, trainers, and cardiologists to establish baseline numbers for both exercise and heart health. Hence, there’s an established body of reliable data.
The idea of giving credit for short bursts of harder exercise makes sense, too. In addition, some studies have shown that the positive effects of these short bursts are cumulative, so having a fitness device that recognizes that is a good thing, too.
But a healthy level of skepticism is a good idea for fat-burning zones. Some fitness experts maintain there isn’t one, and while numerical goals are generally positive, making promises based on them is a little more questionable. To some extent, it’s a marketing technique, so you need to be aware of that when you’re setting up your fitness program.