Hi. Can anyone explain how garmin vo2 max works please? I’m aware it’s not highly accurate and a proper lab test is the only way to get a true vo2 max. I have started my tr training plan and it’s mainly sweet spot just now, so not overly taxing, but garmin is telling me my vo2 max is 37? Is this based on my heart rate from my workouts , or recovery rate ?? If I was to do harder workouts that produce a higher hr would that effect my vo2 reading? My walking one seems to be 45, cycling 37? Using garmin chest strap on bike and garmin vivoactive 3 for walks!!
It doesn’t and you should ignore it.
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Mine regularly came up with 65+, total nonsense.
Plus would say you need 2 - 3 days recovery after a 2 hour easy Z2 ride, IMO all the Garmin metrics are way off.
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Are you using power? Are you recording your TR rides with your Garmin or are you letting TR sync with Garmin Connect? You need power on the bike for the VO2Max to work correctly (I’m pretty sure…) and rides coming from outside sources that don’t take advantage of Garmin’s Physio True Up function won’t be taken into consideration for the metrics that drive VO2Max or the recovery features.
It works fairly well for me on my 935. The actual score may be slightly inflated, but it still shows good trends and the recovery advisor is fairly accurate as well.
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I’ve been tracking the running VO2 max score on my fenix, and I really like it. I use it to check my progress over time, but you can´t get too fixated on the absolute number, and you need to keep a consistent training plan without too much alterations, for the readings to be comparable.
It’s much like the body fat percentage my scale gives me: I know the number is way off, and if I weigh myself in different conditions it gives me completely different results, but if you keep things constant, the relative change over time still has some value.
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I have read online that the Garmin V02 is consistently accurate vs. formal testing. This is a summary from one such page (if it’s on the internet, it must be right? 
):
Wearable conducted an evaluation of their own putting fitness watches to the test – assessing the accuracy of Garmin, Fitbit, and Jabra devices in measuring VO2max. They found that Garmin technology provided a VO2max estimation within 0.3 ml/kg/min of their study participant, which was the most accurate of all devices tested. The high degree of accuracy found in their study remains consistent with other larger scientific studies.[4]
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I’ve had vo2max lab testing a couple times and the garmin is reasonably close for me. I can’t remember how close it was for my first test, but it was about 2 ml/kg/min high for me compared to my latest lab test. I assume the garmin algorithms are done based on correlating factors across a chosen population, so it makes sense that they might get pretty close when comparing results in aggregate across a similar population. I couldn’t find the .3 accuracy reference in that linked article, but I didn’t look too hard. I can’t believe they would be only .3 off for many individuals, so I’m assume is aggregate.
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Easy…it doesn’t
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Same here on a 530 bike computer, the trends follow WKO5 estimates but Garmin estimates are slightly inflated.
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I don’t know how accurate it is but mine tracks very constantly, within a 2 point range and has over a lot of rides. From those who state it is worthless I’d be interested in how you determined it is or maybe a link to something that confirms its uselessness.
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The VO2Max estimate compares your HR (as a % of maxHR) to your power output. Garmin/Firstbeat claim accuracy to within 5% (which is not bad for consumer grade electronics). However, accuracy of the prediction degrades significantly if you don’t know what your true maxHR is (most people don’t) and are just relying on the age-based default. I suspect that this may be the underlying issue for many of those reporting unsatisfactory results.
Theoretically, because it compares HR to power, it is independent of the effort level. Although in practice, differences in aerobic fitness versus anaerobic fitness means reported VO2Max can vary 1-2 points at different effort levels.
Factors that impact HR other than effort can also impact the VO2Max estimate eg. fatigue, poor sleep, illness, etc. Heat will also increase HR for a given effort level, which will impact VO2Max accuracy, although the heat acclimation feature in the Edge x30 series does address this somewhat for outdoor riding (although not for indoors).
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N=1 experience. I’ve used it on my Forerunner 945 with a HR strap for running. It has tended to hover in a range of +/-2 from an actual lab tested value. So is it accurate? If you use power & heart rate then possibly.
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i remember reading a lab study which compared results, cant find the link atm, but outcome was that for most ppl in the study the Garmin value was within 5% of lab test, id call that reasonably accurate, but there obviously are outliers, so bit hard to say
You’re probably thinking of the Firstbeat white paper on the topic. https://www.firstbeat.com/en/aerobic-fitness-level-vo%e2%82%82max-estimation-firstbeat-white-paper-2/
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Developed in a population of runners.
“Validated” on 29 cyclists and uses an age based max HR estimate. If you think that 220-age is accurate for max heart rate, I’d like to invite you to invest in my cold fusion project.
HR is wildly variable to begin with and there isn’t really any meaningful information you would be able to get out of tracking this number that Garmin spits out in the way that it’s calculated that wouldn’t be enormously evident in your regular power data.
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I heard a physiology podcast where they thought it was reasonably accurate for what it is. It needs your HR to estimate the VO2max. Of course it’s not as accurate as a lab test but as an estimate they reckon it’s OK.
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From the very next paragraph in the white paper:
" If the person’s real HRmax is known, the VO2max assessment error falls to the 5% level."
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I’ve had several lab tests over the past few years. The Garmin value has been reasonably close - +/- 2
For what it’s worth, for me anyway, WKO5 is accurate to +/- 0.5. WKO5 is cheaper than a lab test
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