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New VO2max question: Does formula allow increase if HRmax does not increase?

 Hello -

I was wondering if FirstBeat uses variable(s) other than HR to calculate VO2max.

In other words, if I have determined a HRmax from exercising and have then manually entered it into my watch, is my calculated/displayed VO2max going to be constant until such a time I may enter a new value into my watch?

Thank you for your insight!


PS: Garmin Fenix 5S Plus watch

Hi Alexis!

I'm sorry the late reply. Your VO2max increasing means that your fitness is improving. That's great! 

It doesn't need an increase to the maxHR for the VO2max to get better. Simply put: When the VO2max is increasing it means that you are able to run faster with lower heart rates.

As for the white paper, the figures you mentioned are illustrating how the VO2max can be detected also from an uncontrolled run. They also show what kind of data is excluded from the analysis because of unreliable HR data or unreliable speed data. The graphs show the heart rate's relation to the speed. You can find the explanations of the figures from the above text.

Thanks, Nelli! I had not read about using speed ratio in other references, and had forgotten about reading it in yours - much appreciated to you for pointing it out, I did go back and re-read it :) !

What maybe I can ask for a little more help please is … the Y axis in Figures 1 and 2 of the white paper is HR, and I think they are an explanation of how HRmax is extrapolated from linear relationship between HRsubmax and running speed?

What I am wondering about is how my VO2max went up over the past week according to my watch (Fenix 5S Plus), even though my manually entered HR max didn't change. Is there more to calculating VO2max than simply knowing the HRmax?

Thank you again! 

Alexis :)

Hi Alexis,

Thanks for your question. As you can read from our Science site ( the VO2max can be calculated when there is both heart rate and speed data available. Quote from the page: The Firstbeat algorithm analyzes the relationship between HR and exercise speed at multiple points during a training session.

So, the analysis looks into the heart rate vs. speed ratio. Read more about the VO2max analysis from the white paper:

The analysis in your wrist devices uses those HR values which are entered to your watch. If your device can automatically update your maxHR for example, based on your training, then the analysis can use that updated value.

If you have other questions related to our analysis please don't hesitate to contact us via email!

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