HR zones on Luxe do not match my age

[MCB64]

I replaced Alta HR with Luxe. Alta's HR zones were correctly calculated based on my age. Now, my cardio HR is higher than before. My normal brisk walk has the same HR profile as before, but I'm not into cardio zone. 

I set the custom zone. 

Just wondering why the Luxe has different algorithm for HR.

Thanks

[JohnnyRow]

The later devices use a different formula for heart rate zones, and also use Zone Minutes based on heart rate zones instead of Active minutes.

See How do I track heart rate with my Fitbit device?  and scroll down to "What are Heart Rate Zones?"

[MCB64]

Thank you JonnyRow.

I'm familiar with the page and information you linked. Stated calculation /formula is correct.

But zones on Luxe are not correct for my age. 

After I listened Peter Attia's podcast on benefits of zone 2 training (with Inigo San Millan, in 2019), I looked for various formulae to calculate my zone 2 and 3. Different formulae were just few BPM apart from each other. 

Algorithm in Alta HR was not exact (cardio BPM was lower) but closer to my calculations than Luxe. 

I entered a custom zone in Luxe. 

[LZeeW]

@MCB64   I apologize if I am misreading what you wrote.  You wrote that you searched for heart rate formulae, but did your search get you to the formula used by Fitbit in @JohnnyRow's linked article, "How does my Fitbit device calculate my heart rate zones?"  I check the math on my zones from time to time.  RHR is part of the equation and my RHR range has been 46-52 over the last three months.  My math always matches Fitbit's calculations.  Im confident that your Luxe numbers are consistent with Fitbit's Help article.

[Koshka]

Honestly, this is an area where fitbit is inconsistent.  I have a Luxe and just used the default heart rate zones.

According to the Fitbit Luxe User Manual which can be seen online, Fitbit uses maximum heart rate to calculate the zones.  They give an example of this.  That example is the one at the bottom of the link you posted.  That is, the one for "all other devices" and which uses only maximum heart rate and does not use Resting heart rate.

You can see this on page 37 of the Luxe user manual.

https://help.fitbit.com/manuals/manual_luxe_en_US.pdf

However, my heart rate zones shown on the Fitbit app for the Luxe are quite different from the ones I would get using maximum age only.  (My resting HR is around 58 BPM).  The Fitbit app zones do use the formula that uses resting heart rate and heart rate reserve.

Since the Luxe is a newer device it doesn't surprise me that it uses the formula used by the newer device.  However, the online manual says that it does it not use that formula.  So, now I wonder which was actually intended for this tracker.

[JohnnyRow]

@Koshka  I see what you are saying.  I don't have a Luxe (yet) so I can't be sure, but my suspicion is that part of the manual is wrong, perhaps just lifted from a previous manual from before the heart rate zones were changed.  That would mean that part of the 'Help' that I referred you to is also wrong in its use of "all other devices" that you pointed out.  That would have been true before there was a Luxe, and again I suspect the Luxe just did not get added to the list of devices using the newer method. You might try doing the calculations using the newer method that also uses RHR, and I think you will find your zones match that formula.

[MCB64]

Thanks LZeeW. I saw the formula based on HRR.  

The new zones calculation is based on data logged by Alta HR and i do not wear Fitbit 24/7. 

I calculated my target zone and entered it as custom zone.

[Koshka]

I am not the original poster, just a new Luxe owner.  It is clear to me that the Luxe is using the heart rate zones that are based upon using RHR.  I wish this didn't use those.  I have a relatively low end resting heart rate but it really isn't because I am super fit.  I just naturally have a lower end RHR regardless of my fitness level.  Using the new formula my zones start about 20 bpm higher than they would use an age based formula only.  Since I really am not all that aerobically fit, this means I have to exercise at what feels like a very high heart rate just to get zone 2 minutes.  With the old formula I could get minutes at about 20 bpm less.  While Fitbit will allow me to create one custom zone, I can't earn zone minutes by meeting it.

[LZeeW · Accepted solution]

@MCB64   Fitbit uses your sleeping heart rate when it calculates your RHR.  Your fat burn zone threshold might change by a few beats by wearing it in your sleep.  The choice is yours.  Some people just don't want anything on their wrists when they sleep.  With respect to your comment about your brisk walk being in your cardio zone with your Alta HR, the CDC exercise guidelines consider a brisk walk to be moderate exercise.

@Koshka  I saw the error in the Fitbit manual on the day it became available.  I notified Fitbit of the error.

For the both of you, the way to adjust your zones is to create a Custom Maximum Heart Rate, not a Custom Zone.  Tap on your profile picture > scroll down to Activity & Wellness > Heart Settings > Heart rate zones > Custom Max Heart Rate.  Finding you new maximum heart rate is trial and error.  This is because of the multi-step equation to calculate zones.  To get the benefit of exercise, most people should not aim for their "active minute" zones from their previous devices.  You should not be earning zone minutes from a leisurely walk.  A good guideline is to look at your heart rate walking level at 3.5-4 mph (a true brisk walk).  This comes from CDC exercise guidelines of what is moderate exercise.  My advice to users is DO NOT set a maximum max heart rate if a brisk walk puts your in the updated fat burn zone.