This is probably a (very) long shot, but has anyone had the opportunity to compare the VO2Max on their Apple Watch with an actual lab test? I'm curious how accurate the Apple Watch is. Since it can't measure intake/outake of oxygen and carbon dioxide, it's limited to using some algorithm that incorporates heart rate, pace, distance, etc. In other words, it's a (hopefully) good guess. I wonder about my VO2Max because it shows I'm in approximately the 80th percentile for my age, but I never see anybody my age running and so have no basis to compare.