Oh I would be so happy with a FTP of 340. But im not good at cykling. 
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Interesting there is a calculator to estimate vo2 max. I wonder if garmin uses something similar to estimate your vo2 max - garmin thinks mine is quite high, so I doubt it, because when I ran my numbers through this calculator it gives me a more reasonable value.
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I’m convinced that the Garmin number is really just more of an efficiency metric (EF or some variation of Power / Hr) - it completely tracks for me that way.
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Yes, I would agree. I seems to use HR as the primary input and not power.
It also says my fitness age is 20 (I’m 50 lol) - pretty silly thing to spit out.
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I think it relies on both. Needs Power, Heart Rate, and ideally a measured Max HR. But, it goes up as your EF goes up.
I think the number is probably bogus too, but I do feel like the trend is informative if you account for the things that can impact that measurement. e.g. - it plummets when I go to altitude or if I start to get sick.
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With the Tacx Desktop App, Garmin seems to estimate VO2 max every time, even if the effort is below threshold. Not a problem in itself, but at least for me it does not work. Usually it is highest after SS, Threshold or above work. Then the next days when I ride below SS, it decreases every day by one or two points.
I do not witness the same with a Garmin Headunit.
Have you seen most of the world? If you’re active, and seeing as you’re on this forum I’d guess you are, it’s probably not far off.
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I actually find the Garmin value to be pretty spot on for me. I’ve tested my VO2 in a lab twice in the past 5 years and Garmin has been within 1 of the tested value both times.
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The metric I’m referring to is in Garmin Connect, which takes into account all rides that are loaded in. I don’t use the TacX desktop app and I’m not using a headunit right now and that doesn’t impact it. (I use TR to record the ride)
For me - my peak the last couple of years has been dead on after my winter VO2 Block, maybe during the threshold block right after VO2.
I can’t say it’s 100% tied to FTP though. 2023 and 2024 I hit the same peak Garmin VO2 number with differing FTP’s. 2025 I’m 4-5% higher but 3-5% higher FTP too.
When I put my numbers into the VO2 max calculator, I was surprised to see that it aligned almost exactly with what my garmin gives me.
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True, I’m sure I’m way more fit than your average 20 year old even, but I just find it a silly metric.
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Yeah, I’m referring to the same metric. Tacx does not seem to calculate it in the software as it usually does not get updated right after the ride, but some time after.
It is just curious for me that files uploaded by the Tacx App does seem to result in more frequent changes than files uploaded by the Garmin Head unit. It is also possible that they changed the algorithm during my break or that my dual recording with Tacx and TR causes this behaviour.
For me, Garmin updates it within minutes of the ride being uploaded and processed when it originates from TR.
“Tacx” isn’t really involved. I use a Neo2T, have a Garmin Head Unit - but the only two platforms involved are Garmin Connect and TrainerRoad on my end and I would suspect that all processing across the board is done by Garmin Connect as long as it gets valid data files.
If you follow me closely on the forum, you know I sound like a broken record about subjects like this, so pardon me.
That said, do remember that this isn’t direct measure of VO2max. It’s an estimate of your VO2max based on your 5-min power. What they did was they gathered a bunch of pretty fit roadies (average VO2max in the 60s is very fit compared to the population, and likely on the high side even among amateur cyclists). They measured everyone’s VO2max. They measured their maximum 5-min power. Then they fit a regression model between the two. Regression models can be used for prediction.
The thing to remember is that there’s prediction error. They’re really estimating the average VO2max for a given 5-min power output, just like all the max HR formulas estimate the average max HR for a given age. By the nature of averages, some of you will have VO2maxes higher than the formula. Some of you will have lower VO2maxes.
The other thing to remember is that at our level of fitness, gains in VO2max are probably minimally correlated with longevity. If you’re interested in cycling performance, remember that cycling isn’t a test of oxygen consumption, it’s a test of actual performance (and that’s modified by soft skills too, btw).
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If you’re talking about Garmin, this isn’t entirely right, there’s definitely more to it than that although I can’t say what.
I’ve gotten the same “VO2” with different 5 minute Power and FTP in different seasons. And that’s after doing 5 minute MMP tests and VO2 blocks with a bunch of 5 minute efforts as part of the block. Then, I’ve also seen the number go up (or maintain) when I’m not doing any 5 minute Max Efforts at all, and I’ve had different Garmin numbers for very similar, or the same, 5 minute power results
And nobody has ever implied that it was anything other than an estimate, in fact, it’s been said in this thread it’s not a “real” VO2 Max.
Agreed, and heart rate is involved as well, specifically max heart rate.
A couple of years ago my garmin VO2 max started climbing, and climbing. Of course we’d like to think it’s because of our training and improvement, but eventually I had to face that it was seeming too unrealistic, so I went and checked my settings.
My max heart rate setting had changed and was way high, and I realized I had selected a “max heart rate detection” toggle when I had first set it up. Of course one day I got an anomalous high heart rate reading briefly and it reset my max heart rate. That caused my garmin VO2 max to start overreading.
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You mean Garmin ecosystem is using 5-min max effort to estimate?
I doubt it: I usually push with SS/Z4-focused TR plans Garmin estimation into 58-60 range each winter, while 5-min prediction declines to low 50ties (according to intervals.icu) because lack of any VO2max workouts. Only when doing couple week VO2max block in spring (mostly 4x5 intervals), both estimations reach same value again.
They don’t use 5min power.
You can read this whitepaper by Firstbeat (which Garmin acquired) how their VO2max estimate works.
Really important factor is inputting a accurate (actual) max HR in your Garmin profile.
In a way it kinda tracks with EF which in a sense is not that strange considering VO2max is probably a big contributor to EF.
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A quick addition to this - the paper addresses running, it’s slightly different for cycling (just found the Garmin/Firstbeat notes I was looking for) for “external workload” they use power for cycling, speed for running. More here:
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Yeah you are right. I linked the one for running, but you basically just replace pace for power and have the same for cycling. I believe I’ve read a similar explanation for cycling with power once, but could only find this whitepaper quickly. Thanks for adding the blog reference.
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