Heart rate values changed :/

[Latinee]

Hey there ! 

I have being doing hiit workouts for almost 6 months now. I Just verified the information and i can see That until July, my burning fat zone reached 98 ppm at the lowest. Now this value is much higher (120 approx) . I didnt change (at least voluntarily) anything related to the hr configuration. My weight or âge didnt change neither. Does anyone know what could this be related to ? Thanks in d'avance ! 🙂

[MrMarv]

@Latinee -

Two things have changed -

• The Heart Rate Zone formula
• Active Minutes have been replaced with Active Zone Minutes

The Versa 2 firmware update brought into play a new formula for computing heart rate zones - the Heart Rate Reserve method.

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 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.

Hopefully the above helps - and welcome to the boards.