How VO2 Max is calculated?

[Atinch]

Hello Fitbit community,

I have a question about the equation and formula used to calculate VO2 estimations given by my Fitbit Iconic. I currently am sitting at a 60, which is pretty accurate when compared to a VO2 Max treadmill-calorimeter test I did at a university three months ago that measured me at 57. As I dive more into my studies in exercise physiology, I see many different submax formulas, I was just curious what the exact formula isn’t for the Fitbit.

Any insight would be greatly appreciated.

Moderator edit: updated subject for clarity

[JohnnyRow]

Hello @Atinch.  Welcome to the Fitbit forums.

I don't know the exact answer to your question (and I doubt anyone on these boards would know), but maybe someone will.  But here is Fitbit's help section about it, in case you haven't found this yet.

What is my cardio fitness score?

I think somewhere in there you will find that it gets set (only) when you do a run on level ground for at least 10 minutes, perhaps, not sure about this, needing to be started from app rather than tracker.  And it might take a few such runs to recalculate.

Without that running measurement, it is just an estimate based on you resting heart rate and other physical data.

[Colinm39]

@AtinchTry these formulae of Vo2 using RHR and running and they may help understand what Fitbit do with their calculations.

This one Gives me the same answer as my Cardio Fitness score but no underlying formula

This link has a few formula and maybe these will help but these give me 1 point less than my range of Fitbit's Cardio Fitness score.

This link is more complex but may help understand the Fitbit 10 minute running test.

[pointy101]

Vo2 max is part of the medical for my work .

They  use the Chester step test to assess us.Its like a bleep.test but on a step over a 10 Minute period . 

[EdsonFitbit]

@Atinch Welcome to the Fitbit Community. 

Thank you for your question about the equation and formula used to calculate VO2 Max. What we can tell is that your cardio fitness score is determined by your resting heart rate, age, sex, weight, and other personal information. Specifics about the algorithm used can't be disclosed since it is proprietary information. 

@pointy101 @Colinm39 @JohnnyRow Thanks for your support and comments.

If you have any other question, please don't hesitate to contact us at any time.

[KievT]

Hello Edson,

I understand why the algorithm cannot be disclosed due to proprietorship but I wonder if there has been any studies that has validated the VO2 max estimate with actual VO2 max from a cardiopulmonary exercise test (CPET/CPX). If there is any, link to it would be appreciated!

[KievT]

Do you think the VO2max estimate is reliable?

[KievT]

Any idea how different the VO2 estimates would be if you ran on a treadmill vs outdoors? with vs without GPS?

[redchillipadi]

I am interested in this too as I might start using Fitbit in health projects. I found a small study here https://pubmed.ncbi.nlm.nih.gov/28767091/ which showed that Fitbit VO2 Max was about 5% higher than the measured value on the treadmill.