Active minutes vs cardio?

[MotherM]

I would expect these two measurements to align with each other, but they don't.  Here's an example.  On a short walk today, I had 11 minutes peak and 1 minute cardio, though the walk was 33 plus minutes.  (no fat burn, no below, just total 12 recorded.

That same walk gave me 32 active minutes.

Earlier in the day, pruning a tree for an hour gave me 19 active minutes and 27 cardio, 35 fat burn.

In case it matters, I'm almost 80 and my resting HR around 55, so I know my zones are pretty amazingly low.

Will some member of the community please help me to understand?  Many thanks!

[Heybales · Accepted solution]

Active minutes is based on basically calorie burn.

Is it 3 x your base (BMR) calories for a minimum 10 min  of time.

HR is an estimate of calorie burn, and where your HR happens to hit in the zones based on age, means the 2 things are not related.

I'd suggest it appears the middle part of your cardio zone is where the calorie burn is starting at about 3x your BMR to count towards Active minutes.

Oh - if you have been this fit for awhile, I'd suggest the old-and-replaced formula for HRmax of 220-age is especially not accurate for you - your HRmax, and therefore your zones - are likely higher.

A higher HRmax would effect your calorie burn (lessen it actually), and therefore the point you reach the 3x point for Active.

[Baltoscott]

Hi @MotherM.  Do you have a Charge 4?  With that model Fitbit introduced Active Zone Minutes, which are a bit different from the older Active minutes metric.  For Active Zone Minutes, you get double (2minutes) credit for each minute of HR recorded in the peak or cardio zones, and 1 minute credit for each minute in the fat burning zone. Since you say you didn't have any minutes in the fat zone in your walk example, the math still isn't quite right. The 11 minutes peak and 1 minutes cardio should translate to 24 Active Zone minutes.  

If you are talking about Active Minutes (i.e, you don't have a Charge 4), as @Heybales notes, those are not directly related to the cardio or peak zones. They are calculated based on continuous motion detected by the accelerometer in your device not your HR measurements. In fact, the metric can be generated even by Fitbits that don't measure HR. You can read more about active minutes here, but the main takeaway is the active minutes are related to tracker movement, while your cardio is based on changes in your heart rate. Active Zone minutes, on the other hand (for the Charge 4, and probably future models, and likely the Versa family through a future upgrade), are based on heart rate.