The only workout types that produce a VO2Max figure are;
outdoor running and walking and hiking.
And VO2Max isn't based on age,my neighbour is in his 80's and he checks his figure on a regular basis.
Apple says;
Your Apple Watch gives you a cardio fitness ESTIMATE by measuring how hard your heart is working during an outdoor walk, run or hike.
To estimate your cardio fitness level, your Apple Watch also takes into account your:
Age
Sex
Weight
Height
Medications that may affect your heart rate
It can take at least 24 hours wearing your Apple Watch, followed by several workouts and passive measurements with your Apple Watch before you receive an initial ESTIMATE.
Certain conditions or medications that limit your heart rate may cause an overestimation of your VO2 max.
Are VO2 max predictions accurate?
The relationship between heart rate and VO2 max is not precise, and it varies from one individual to another. So Apple’s predicted VO2 max may not be very accurate. The estimate is also dependent upon your Apple Watch’s heart rate sensor. And while that’s pretty good, it is not infallible.
VO2 max relates to maximal exertion. So you’ll need to log a pretty intensive workout to generate a reading. And you’ll need to sustain it for at least 20 minutes.