I had the same problem measuring my VO2 Max. I don't swing my arm when I walk so even walking outside didn't help me. I got my reading from another device (not a Garmin device) and imput it manual, but the Garmin software doesn't update that number. Since calculating a VO2 Max doesn't require movement, I do not understand why a GPS is required. The support article does say that putting the setting to all-day RH readings will generate a VO2 Max number, but I haven't seen this happen. It may be that manually entering a number removes this option. You could try putting it to all day and see if it works for you.
The support article does say that putting the setting to all-day RH readings will generate a VO2 Max number, but I haven't seen this happen
I think you misunderstood some statement. For measuring the VO₂max you need to measure not only the HR, but also the respiration rate, and the effort. You need to exercise hard to have the VO₂max measured (typically minimally 10 resp. 20 min with HR at least 70% of the max HR).
Watches announced after April 2017 that feature an optical heart rate monitor are capable of generating VO2 max from all-day heart rate data. VO2 max generated from all-day heart rate will only show if you have not generated VO2 max from another source above, unless the all-day heart rate VO2 max is better than VO2 max generated from other sources.
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Exercise as in intensity, but not as in GPS movement. In the doctor's office, the patient doesn't GPS anywhere, they work on a treadmill. On an athletic tracker, one should be able to enter a 2 minute cool down period at the end of a stationary workout and get the same data.
In a real test for the VO2 max you got a face mask that measures your breathing. Since you don't have that when you are running with your watch a different algorithm is used which needs your actual speed and some other variables and parameters to get an accurate enough value.
My cardiologist used the Astrand Treadmill test in his office using a treadmill and an EKG set up (no mask.) There is also a test called the Cooper that can be done on a treadmill. There is another, I don't know it's official name, but it is generally referred to as a fitness test and involves working up to anaerobic level, then stopping the work-out to measure the heart rate after one minute, then two minutes, to determine recovery. The quicker the HR returns to non-active rate, the better the rating. It mostly works like the other two, but doesn't require a treadmill. The Garmin devices can test those numbers by checking the heart rate after one minute, then again, after two minutes and finally doing the math to report the number.
Garmin watches do not measure EKG. It might come soon and then we might see other methods for measuring VO2 max.
Cooper's test needs an accurate distance. The watches have a hard time measuring an accurate distance on a treadmill and pretty much always needs to be calibrated afterwards. Therefore a GPS is needed to measure distance.
The recovery method might be too inaccurate and depends a lot on other parameters that are easy to get wrong like the anaerobic level. I don't know. Or the current method is considered to be more accurate and works for most people.
