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# Garmin VO2 calculations

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How does this work: did a PB 5k on Saturday and VO2 was at 49 (I’m 52 year old and a relatively new runner). Then yesterday I did a steady 10k but with 180m of elevation and the VO2 dropped 2 points! Does the Garmin not take into account elevation? My heart rate was never above 160 but the pace was slow at about 6 minute km,  it I was surprised (no, gutted) that the BO2 went down!

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Your Garmin can't know your VO2, those figures are just based on assumptions and a formula or two.   You need to do a lab test for a true VO2 reading.   Exactly the same with calories, your Garmin can't know your calorie expenditure.

Have you tried putting your 5k PB in a race calculator?  If the prediction for a 10k is lower than your actual 10k run then of course it will assume a poorer VO2
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> Your Garmin can't know your VO2, those figures are just based on assumptions and a formula or two.

yes, I know that, and I know that it's only a very vague approximation, but given that it knows you're running up a hill it would add that information to the assumptions. it's pretty fundamental to any formula that it uses to make the estimate.
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You're right, it doesn't include any information about elevation or terrain.
All it knows is that you were working harder for a slower pace - therefore a lower estimate.

It is only an estimate, and not something to rely on as a marker of progress because of this.
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<blockquote class="Quote">
<div class="QuoteText">You're right, it doesn't include any information about elevation or terrain.
All it knows is that you were working harder for a slower pace - therefore a lower estimate.

It is only an estimate, and not something to rely on as a marker of progress because of this.</div>
</blockquote>
So I guess that the calculation is based on track running at sea level?You would have thought that elevation would be factored into the algorithm, even taking a guess at it couldn’t make it any less of a vague estimate...
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I don't think it is as useful a metric as you suggest if elevation were included. You'd encounter the same problem - consider a smooth tarmac hill vs the rugged coastal path. Then there's the small task of somehow incorporating this into a biological estimate?

The true way to know your VO2Max is through a treadmill lab test, which still is only an estimate.
However, when it comes to your watch - be happy when it goes up, and don't worry so much if it goes down. If it was a hillier run bringing it down, it won't be long until it goes back to where it was.
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