You may have opened a can of worms with asking that question - there have been some heated discussions on the boards about the subject.
It seems to me that 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".
Coupled with that is the redefinition of Heart Rate Zones based on the new "Heart Rate Reserve" formula. The difference, for me, is shown in the chart below - my heart has to beat 23 more bpm to be "In Zone":
For instance, you take a 30 minute walk without getting your heart rate up to at least Fat Burn.
- 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.
- And you cannot select which "active" definition you use.
For Active Zone Minutes, you receive one Active Zone Minute for each minute that your average heart rate for that minute is in the Fat Burn Zone. You receive two Active Zone Minutes for each minute your average heart rate is in either the Cardio or Peak zone.
And example is shown in a recent treadmill exercise record of mine:
The below zone tracks in the middle of the exercise come from what I believe is a flaw in the Treadmill Exercise app - a flaw that is similar to a reported flaw with the Apple Series 5 device's exercise heart rate algorithm, as well.
BTW, I have noticed that just because my Fat Burn zone starts higher than it used to, I still burn approximately the same number of calories on a one-hour treadmill session as I did under the traditional zone calculation. Maybe that is why the new zones are commonly referred to as "Training Zones" and many of the sites that talk up the Heart Rate Reserve formula are sites targeting athletes and not John and Jane Doe just trying to get healthier in general.
Have a good day.
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