My understanding is that Garmin is highly dependent on your training times and powers. The true lab Vo2max test is what's going on in physiologically.

My n=1 results:
Garmin run vo2: 58
Lab test run vo2: 72
Garmin bike vo2: 59
Lab test bike vo2: 64

Yeah Garmin's VO2 estimates are useless. Mine never changes despite improvements in all quantifiable performance metrics. It's not intuitive at all, doesn't seem to "learn".

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I regularly see my values adjust as fatigue increases or decreases and my performance changes accordingly. As well, longer trends in this number are likely more valuable over time. What if you interpreted this as a current functional number rather than an absolute performance capability?

I wouldn’t trust Garmin metrics period. I’ve seen so many companies make disastrously bad statements about things they’re calculating. Calculating is different than measuring. Measurement error is real. Calculations often compound measurement error. Bad decisions about how to perform such calculations not only compound error but just make many of the numbers meaningless. I’ve seen too many disastrously bad decisions in software around fitness based calculations to trust anything unless their algorithm has been verified to correlate extraordinarily tightly with actual tested VO2. At which point, if such a correlation were to exist, I ask why do we care about VO2 enough to present it daily, when it only makes up a tiny percentage of performance outcomes between athletes within a given fitness range.

I digress. Unless a metric is meaningfully improving your life and decisions, I’d ignore it and delete it if possible.

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Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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I agree with everything you say... From a purely engineering or scientific perspective. Measurement errors, goodness of fit, sensitivity analysis... All that jazz matters; that's particularly true if you try to create an absolute inference with real units. I also believe in rigorous, published, reviewable data on a metric inference... Even if the algorithms themselves are held as proprietary.

That said, I do find that the garmin vo2 metric is consistent and correlated with my actual performance enough to be a useful measure of progress towards a goal or milestone. I do not think it correlates well with vo2max with units of ml/kg/min. There are other measures of performance and progress, for sure. So, it's just one more bit of data---but, it can be informative of progress, in combination those others.

One just has to have the right perspective on all these various data. No one metric is very meaningful by itself. No one should take any single test, or metric, or trend in a metric in isolation.

No one should devise a race plan around a garmin vo2 score. But, a vo2 score correlated with prior race results, and prior / current training records does provide strong indicators for current expectations. In my personal experience...as long as garmin doesn't futz with the algorthims... Which they do seem to do, every now and again... Making historical comparisons useless.

I admit that degree of analysis may not (is not) everyone's cup of tea, and they would be better off not using such data as it's more likely to lead them astray.

Well said. I can get onboard with that.

I'll add this to the milieu in case it's helpful to anyone.

There are always psychological - and therefore physiological - effects of tracking a metric. Sometimes they're beneficial and sometimes the opposite, and sometimes the benefits and costs change, and even reverse, over time. Assess with care.

If a 'metric' (like Garmin's VO2max) ever makes you feel concerned, then throw it out until it feels genuinely completely unconcerning. Seriously. The presence of even subtle negative emotion in self-analysis hurts health and sport performance far more often than it helps it, especially in the long-term. You have more important things to be thinking about.

PS. Psychology (emotion and cognition) affects physiology so innately (and vice versa) that it's remiss to discuss psychology independent of physiology, especially in sport. I may start using 'psychophysiological' as my default word instead of psychological.

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Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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📱 Check out our app → Saturday: Pro Fuel & Hydration, a performance nutrition coach in your pocket.
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