I'm 46 years old male. Been a kickboxer all my life. I can do 100 proper form press ups in a row, sometimes up to 150 if I push it. On week days I do (every day) 100 situps in 5x sets of 20, same with squats. Press ups 5x sets of 30 normal then 5x sets of 20 in various positions ending with a stress test of my maximum which is normally between 60 and 100 when fatigued. I do x2 intense coached kickboxing sessions per week including endurance rounds on the heavy bag (minus sparring at mo due to social distancing rules). I do a two mile run every day (it's just a trainings run so I don't bother going further and I only get a 30 minute lunch break)
On weekends I take a break and do a couple of 4 mile walks.
Yet, according to Garmin and my Vivoactive 3 watch, my VO2 max is 42 - which is "fair" .... it did go up to "good" once but then dropped again after a run where I went under trees and it thought my pulse was 150 at walking pace due to poor GPS signal! I am 100% convinced that I am fitter than that!
I am neither under nor over weight. What's going on? Why is my apparent VO2 Max so low?