Be advised that the Heart Rate Zone formula has changed if you are on Versa firmware version 71.6.19. Also, Active Minutes have been replaced with Active Zone Minutes.
First the zone calculations:
The Heart Rate Zone calculations have moved from the Traditional formula which are straight fixed percentages (50, 70 and 85%) of your Max Heart Rate which is defined as subtracting your age from 220. For me, as a 68 year old male, my Max Heart Rate is 152. Traditional zone values for me are shown in the first data row below.
The new formula being used by many FitBit devices, including the Versa 2 as of the latest release, use a value called Heart Rate Reserve. Subtracting your resting heart rate from your max heart rate results in that reserve.
40% of the reserve is added to your resting heart rate to establish the beginning of the Fat Burn Zone.
60% of the reserve is added to your resting heart rate to establish the beginning of the Cardio Zone.
85% of the reserve is added to your resting heart rate to establish the beginning of the Peak Zone.
The new Heart Rate Reserve formula zones for me are shown in the second data row below.
Actually, my Max Heart Rate is 120 (80% of traditional max) because I take Beta Blockers that throttle down my heart rate even during exercise. This was confirmed with my Cardiologist September 3rd during my semi-annual office visit and is discussed in the Harvard Medical School Harvard Health Letter from November of last year. My heart rate zones utilizing the Heart Rate Reserve formula and using my redefined Max Heart Rate is represented by the third data line below.
FitBit has also apparently rethought its definition of "activity".
- It used to be "Is your body active".
- It is now "Is your heart active and how active is it".
For instance, you take a 30 minute walk without getting your heart rate up to Fat Burn, which isn't that difficult to do.
- In the past you would be awarded 30 active minutes, or close to it if you were burning more than approximately 3 times your resting calorie burn (BMR) and you don't have to be in Fat Burn to do that.
- Now you will receive zero Active Zone Minutes because you were "below zone" for the whole walk.
You receive one Active Zone Minute for each minute your heart rate averages in your Fat Burn Zone.
Your receive two Active Zone Minutes for each minute your heart rate averages in either your Cardio or Peak zone.
When I say "each minute your heart rate averages" - each minute of your devices "clock" not the timer associated with your exercise. If you start an exercise at 20 seconds after the "top of the minute", your Active Zone Minutes will update the exercise AZM display (is selected) at 0:40, 1:40, 2:40 etc into the exercise.
I hope this helps explain some things and welcome to the boards.
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Forgot to mention that you can verify the changes to your zones by checking out the zones in the mobile app.
Tap on the heart rate tile on the Today screen.
On the Heart Rate screen tap on the gear icon at the top right, you will be shown something like this:
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