How Apple Watch Counts VO2Max How Fitbit Counts VO2MAx

What is difference between Apple And FITBIT

Which is more accurate

Probably neither. VO2Max measured by wristwatches is mostly an estimate and accuracy can be verified only with proper lab test but I don't think many people do that (maybe except pro-ahletes).

I am thinking they probably use similar technology, but unless someone owns both and can do a comparison, you will probably need to read reviews and key differences. You can probably just type your question into a search engine and get some info quickly.

You can search the web for how to estimate vo2max. There are a number of methods. Some use your resting heart rate, and others try to estimate based on your heart rate while running over a distance using GPS. At best, all are estimates.

@PHS273 Apple has this document available and it describes how it tested and validated its VO2max algorithm. Fitbit tends to be very proprietary about these things. I can't find a device to device comparison.

A VO2max from a fitness tracker estimate is only as good as the device's optical heart rate monitor and its GPS accuracy.

@LZeeW this is a very interesting paper 👍 Thanks for linking it! It actually shows that the watch doesn't really measure VO2Max but rather predicts it based on statistical data. With Garmin, it gets even more complicated (I tried to find something similar to Apple's document but nothing as open can be found) because you have VO2Max for running, cycling, trail running, walking, and kind of estimate for daily activity. I agree that the VO2Max depends heavily on HR but also on the GPS (which can be quite wonky, too). For my own measurements, I use chest-strap (probably you already noticed that I don't trust optical HR when it comes to exercising). Interesting thing is, that my cycling and running VO2Max are slightly different (different methodology, cycling VO2Max requires a power meter and HR, GPS isn't necessary). My Sense doesn't fall far with VO2Max estimation despite I don't wear it 24/7 (I believe this is because of a number of runs with the all-out effort which are the main source of my estimates). There are differences (approx. +/-2) but at least it doesn't display VO2Max as a range (I could never get my old Ionic to show me a single number rather than a range). But then there is the possibility that all my devices are totally wrong. Without a proper lab test, I won't know that. That's why I treat wearable VO2Max as an interesting metric but nothing more and definitely not as useful as for example FTP or lactate threshold.

I agree @t.parker. The document describes using a linear model to estimate VO2Max from submaximal tests. Apparently there is relatively good correlation using this method, which is physcially much more accessible to the average person.

That said, these are still estimates, but I think the real utility is not in the absolute numbers, but rather the trend of the numbers for each user, which I think is true of a lot of the Fitbit (or other tracker) data. Calories are a great example. I wouldn't trust the number of calories burned to determine a diet plan, based on caloric deficit. However, I would trust that if I increase the number of calories burned during exercises, from from one week to the next, that I probably exercised more/harder.

My Fitbit tells me my Vo2 max is 46 my Apple Watch 7 tells me it’s 20 🤔

@SunsetRunner how do you test VO2Max? I mean, do you include flat sections of 10 to 12min runs with GPS (all-out test)? Also, if you judge your fitness you can probably tell which one is closer to reality. Based on VO2Max ranges, Apple tells you that your VO2Max is 'poor' and Fitbit tells you 'average'. This is a big enough difference to be able to tell which estimate is more realistic just by judging your perceived fitness level.

Glad to see this comment. I’m exactly in the same boat as you. I changed from Fitbit Charge 5 to Apple Watch 7, fitbit shows 43 (over average) watch shows 22 (below average) Cardio Fitness level 🤔