Comment by NoPicklez

I don't see how they are considered a health fad, they're extremely useful and accurate enough. There are plenty of studies and real world data showing Garmin VO2Max readings being accurate to 1-2 points different to a real world test.

There is this constant debate about how accurately VO2max is measured and its highly dependent on actually doing exercise to determine your VO2max using your watch. But yes if you want a lab/medically precise measure you need to do it a test that measures your actual oxygen uptake.