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Why Your Garmin VO2Max is Useless

Your VO2Max is the maximum amount of oxygen you can take in and use per minute and is a good indication of physical fitness. Although not the sole predictor of race performance, a high VO2Max is a pre-requisite for any successful endurance athlete.

So surely estimating your VO2Max would be a good thing?

Your VO2Max is only a small piece of the puzzle when it comes to improving endurance performance. Your speed/power at your anaerobic/lactate threshold, running economy/cycling efficiency all contribute equally to success, which is why the benefits of a VO2Max test extend far beyond working out your VO2Max value. Measuring the above ( ) can establish where you need to improve.

A VO2Max value is by itself does not provide enough information or data that can help you as an athlete, which is why VO2Max calculators or the Garmin reading on your watch is pretty useless. Although the calculations and algorithms maybe decent estimations, they are not accurate reflections of your physiology and don’t provide you much other than bragging rights.

So what can you do?

For cyclists

A Ramp/Step test

Like a lab test, a ramp test is a progressive step test that starts relatively easy (75-125watts) and increases in power every minute (usually by 25watts) until complete failure. Your Maximum Aerobic Power (MAP) or power at VO2Max is calculated by adding the power you produce at the final stage of the test you fully complete, to the % of the increment of the stage you didn’t complete.

So if you completed 350watts, and failed 30s into the 375watt step. Your Maximum Aerobic Power would be 350 + (25*0.5) = 362.5watts.

You can then calculate or estimate your FTP by multiplying it by 75%.

However, the problem with these tests is that they’re only providing you with a small piece of the puzzle and an estimate at that.

We are all different, and your FTP will not necessarily be this percentage of your V02 max. Likewise, if you do an FTP test, you’re only guessing your VO2Max.

What can you do if you’re a runner?

One way to estimate your VO2Max zone is to establish your maximum heart rate. To do this simply keep running up and down a hill until it doesn’t go any higher! Your VO2Max zone would (95-100% of your max heart rate). As discussed in a previous post (, something like a Critical Speed Test will provide you with better information.


In short, VO2Max calculators are useless, your Garmin VO2Max calculation may be a proxy to improvements in your running or cycling. Still, it is not a maker for your actual VO2Max.

This is the reason why VO2Max Testing or metabolic profiling becomes so useful. By accurately measuring your V02 max and your anaerobic threshold, the power and speed at your anaerobic threshold provides so much more data to help maximise your training, reduce the chances of injury and ultimately improve your results more efficiently.

A full metabolic test can establish your:

  1. VO2Max and pace/power at VO2Max

  2. Lactate threshold and pace/power at your lactate threshold (FTP)

  3. Aerobic threshold

  4. Fat max – how much fat do you burn at different intensities

  5. Glycogen – how many carbohydrates do you burn at different intensities

This will give you far more information about how to establish your training zones accurately and provide you with the insights in where you need to improve. Is your FTP close to your max aerobic power? Is your FTP very low in comparison to your maximum aerobic power?

If you are interested in metabolic testing to help improve your insurance performance, then visit

Or if you have any questions about nutrition and performance, send them to

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