Image source: Garmin

New study quantifies accuracy of Garmin Vo2Max readings

A new study has quantified the accuracy of Garmin Vo2Max readings. It turns out they are not too far off the mark.


Garmin Vo2Max quantifies your level off fitness

Anyone with a Garmin watch knows the device on their wrist has the ability to spit out a Vo2Max value. We won’t go too much into what this is. You can read our separate piece on this and the benefits of tracking the metric with wearables.

For the purposes of this article, let’s just say that Vo2Max is a measurement of how well your body uses oxygen when you’re working out at your hardest. It reflects the aerobic physical fitness of the individual, and is an important determinant of their endurance capacity during prolonged exercise. The higher your reading, the better.

Essential readingTop fitness trackers and health gadgets

The best way to quantify your Vo2Max is by getting tested in a traditional lab setting. But this can be quite pricey and is not very convenient. Companies such as Garmin aim to simplify the process with fitness trackers and smartwatches. This makes the info accessible to all, it allows for more frequent readings and that type of info is used to prescribe exercise intensity.

To arrive at the estimate, Garmin starts off by combining info on your resting heart rate, age, gender, weight and other personal data. This is supplemented by information gathered during exercise analysing the relationship between your pace and heart rate. Properly defining your heart rate zones is important as speed data from “reliable” segments is used to calculate Vo2Max. On newer watches heart rate variability info is also used.

Here’s how Garmin groups the Vo2Max scores. The first table is for men, the second for women. Where do you fit in?

Garmin Vo2Max scores
Garmin Vo2Max scores

How accurate is Garmin Vo2Max – new study

A new study published in the International Journal of Sports Medicine aims to quantify the accuracy of Garmin devices when it comes to estimating Vo2Max. For the research the scientists equipped 23 runners (11 male and 12 female) with a Forerunner 245 watch. This is one of Garmin’s more popular devices for runners.

The study participants visited the laboratory twice during the observation period to determine their Vo2Max during a treadmill ramp test. This information was compared with three outdoor runs where the metric was tracked by the Garmin watch.

So what do the results show?

The good news is that for runners that fall in the Vo2Max range between 44 mL/kg/min and 55 mL/kg/min, the mean absolute percentage error when validating against lab tests was just 4.1%. The criterion measure revealed a coefficient of variation of 3.5% in this range.

The bad news is that the results were less accurate (discrepancy of 7.1%) for runners with lower (below 45 mL/kg/min) or higher (above 55 mL/kg/min) Vo2Max. Which means these individuals should judge the Vo2Max value dished out by their Garmin watch with more caution.

On average, the Forerunner 245 showed an overall discrepancy of 5.7%. This leads to the conclusion that the watch can be used to track changes in Vo2Max. However, using this measurement to prescribe exercise intensity has limited application. This is because of the variations in accuracy that appear depending on the actual value of an individual’s reading.

What about other studies?

These figures broadly correlate with other studies. Research from a few years ago used similar procedures to estimate the efficacy of the Garmin Forerunner 920XZ when it comes to dishing out Vo2Max values. They observed a 7.3% discrepancy against lab tests.

Another paper published in 2021 in the International Journal of Exercise Science utilised the Fenix 6S. This showed similar results.

Firstbeat Analytics, which is now under Garmin’s wing, also conducted a study. They monitored 79 individuals during 2690 runs over a 9 month period. Garmin’s Vo2Max estimates were compared with four lab tests. The results show that there was a 5% error on average (less than 3.5ml/kg/min) between the readings.

The caveat of that study was that the accuracy largely depended on how accurate a person has set their HRMax. If it is underestimated by 15 bpm, the Vo2Max error climbs to 9%. Overestimating by the same amount leads to a 7% error. So make sure you have this value set correctly.

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20 thoughts on “New study quantifies accuracy of Garmin Vo2Max readings

  • As a scientist, I would say the number of cohorts in this study was too small to draw a conclusion of accuracy

    Reply
    • You have to be careful with the measurements. I’m 65, and when I run on nice, flat streets, I measure in the 46 range. However, most of my running is on rocky, rooty, hilly trails, where I’m much slower and have a higher HR . Then I measure around 35. It doesn’t know anything about your efficiency due to running conditions.

      Reply
      • The Garmin documentations states this. You should select trail mode so it doesn’t calculate your v02 for runs on those terrains.

        Reply
    • I would also add there is probably a scale factor missing in the equation used by Garmin in their calculation of VO2. In the small study there seems to be consistent results above and below the median that suggest a non-linear scale.

      Reply
  • Oooo. Fantastic….. But given that my $1200 fenix 6 ultra doesn’t connect with my phone, it’s useless.

    Get your act together, Garmin, before you start patting yourself on the back.

    Reply
    • Decent sleep tracking is top of my list…

      Reply
    • Lol…wut? You should probably contact Garmin customer support instead of crying into the void of the internet.

      Reply
    • It’s your phone not your watch. I’d be willing to bet user error. These watches are great.

      Reply
    • I use an app called reconnect Garmin watch. I have Fénix 7 sapphire but the connections is horrible

      Reply
    • User error? Fenix6 sapphire works great???

      Reply
    • Snap. I run 5 days a week and capture only two or three of them on my phone.

      Reply
  • Does it really matter, elite runners/ athletes will go to lab for a true VO2max reading, anyone else it’s just a good guideline as to whether you’re getting fitter or losing fitness.

    Reply
    • True that! It’s just another convenient tool which just is not a fully equipped lab but amazing in its own right – imagine this 20y ago! Whichever modern decent quality sports watch you pick will probably do for recreational use for 95% of the users IMHO, as a sort of crude guideline at least and you could optionally even tune it by setting your heart rate zones correctly after a professional lactate test in a lab if you really want to max out the capabilities. Comparing too much between brands and watches while working out is rubbish as there will always be discrepancies. Just pick one you like and stick with it as a reference I’d say 🙂

      Reply
  • I have learnt Garmin is very good at estimating values with added help of the watch features.
    Your personal settings are therefore extremely crucial for best reading.
    Its perfect for tracking your personal fitness trend, however I doubt its actual ambient accuracy. Comparing values such us heart rate and / or breathing rate by two watches (one on each wrist) shows large discrepancies.
    Nevertheless its an amazing tool and fantastic insentive to train better / harder.

    Reply
  • My V02 max on my fenix 6 pro is 49, in the lab it’s 53. Not bad for a watch.

    Reply
  • I tested in the lab last year for both bike (52) and run (50). The Garmin 935 had me at 52 and 51, respectively. I recently did a significant 6 week training block followed by a week of cycling at altitude (10-12K ft.), culminating in a 71 mile ride with 8000 ft of climbing. The Garmin increased to 54. I typically finish top 5 at multisport national championships. It would be good to see what the sensitivity is for age. I am 66 years old. Yes, superior VO2 Max for my kid’s ages. 🙂 BTW – I ALWAYS use a chest strap for HR. Wrist HR always messes up my data to the high side.

    Reply
  • Good and relevant topic for an article.Much appreciated! It is important we keep monitoring the quality of this type of data as it is more and more ofte used for diagnosis. And this medical use seems to be justified according to the above and the 2 other referenced articles. I have a Garmin Fenix 7x sapphire solar – and its the best watch I’ve ever had!! Works perfectly.

    Reply

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