Apple Watch recording wrong cardio fitness levels

Too many times to count I have seen my VO2 max score go down compared to walking or jogging exact same path exact same distance with overall faster speed and overall lower heart rate than previous workout that got higher score. Sometimes I even see score go down when not only faster speed and lower heart rate but also greater distance.

Additionally frustrating is weather evidently not used in cardio fitness algorithm. When heat and humidity make it like jogging in steam room, obviously heart rate will be higher other things being equal and should not be indicative of reduced VO2 max.

Perhaps most frustrating, as I have seen in other comments, is how commonly my highest scores are for my easiest workouts, some so easy it’s a stretch calling them workouts.

[Re-Titled by Moderator]

Original Title: Cardio Fitness seems to have no clue