I posted some notes in this other topic on vo2max struggles:
After a block of two sessions per week crushed me, I’ve had good luck of late by dialing it back and starting really slow - 1 vo2 interval, 3-4 days of endurance, 1 vo2 interval, 3-4 days of endurance, 2 Vo2 intervals, etc.
I’m nailing the hard start intervals with practice and now I’m pretty comfortable pushing 120-125% for 5 minutes. I’m ready for a bigger block next.
I’m probably going to try 40/20s just to see how they go.