Originally Posted by
MoAlpha
Yup. I believe most wearables use an algorithm based on HR response to exercise and a set of population tables for age and sex. They derive a relationship and estimate the max, based on submaximal data. Probably accurate within a few points in most people.
Weight, too, but yeah, sounds about right.
Not surprisingly, my new Fitbit, which seems to do a poor job of reading HR on a bike ride outdoors, dropped my Fitbit VO2max estimate by 4 points or so. Bastards.