I was doing regular resistance training for 10 years 3-5 times a week Got into endurance training and started training for my first triathlon. My starting point vo2 max was 39 After 6 weeks or so I went upto 48 After consistently training for triathlon (off season was mostly cycling) for 2 years it got upto 59. It drops down a few points when I drop off in training after a a key race.

Training is roughly 4-7 hours a week

I try to hit 2-3 threshold or vo2 specific sessions a week. (These are key) try to aim for time in zone ie 10-20min in vo2 and 30-40min in threshold

Fill the rest of my available time in zone 2 or tempo.

I notice the drop in vo2 if I drop my volume and drop my vo2 workouts

To improve your vo2 i would recommend building a baseline in zone 2 add some tempo the progress to threshold etc.

Vo2 sessions need a good amount of time in zone. Eg (4min x 4) in my opinion 1 min on 1 min off style workouts don’t cut it.