Hello xersyzguy43L,
It sounds like you have some questions about VO2 max accuracy on your Apple Watch. We know how important this is for you, and we will help get you to the right place for answers.
How Apple Watch estimates your cardio fitness levels
Apple Watch Series 3 or later can record an estimate of your VO2 max using the heart and motion sensors during an Outdoor Walk, Outdoor Run, or Hiking workout in the Workout app. Apple Watch supports a VO2max range of 14-65 mL/kg/min that is validated for users 20 years or older.
To estimate your cardio fitness level, your Apple Watch also takes into account your:
• Age
• Sex
• Weight
• Height
• Medications that might affect your heart rate
It can take at least 24 hours of wearing your Apple Watch, followed by several Outdoor Walk, Outdoor Run, or Hiking workouts* and passive measurements with your Apple Watch before you receive an initial estimate.
If the Health app detects that your previous cardio fitness estimates could be more accurate, you'll have the option to update your data. In Cardio Fitness, tap Update under Update Your Data. After you update, the Cardio Fitness Data Updated notification shows you the results of the update and how your estimates changed.
This info is located in this support article: Track your cardio fitness levels - Apple Support
You may also look into calibrating your Apple Watch for improved accuracy: Calibrate your Apple Watch for improved Workout and Activity accuracy - Apple Support
If you need continued assistance, please get in touch with the Apple Health & Fitness support team via this link: Get Support > Apple Watch > Health & Fitness.
Farewell!
