Quick suggestion – if you are struggling with Vo2 work currently try this…it’s worked for me in the past:
Every time you have a Vo2 workout coming up in your calendar, replace it with either Huffaker (my preference) or Mills. The reason is as much psychological as it is physiological.
In the case of Huffaker, the intervals build for the first 30 seconds of each interval, which is nice. Then the individual intervals build from 110% → 115% → 120% and then come back down. to 110% to finish – and it helps to know that watts are going to start coming down. Helps me hang in there. Once I nail Huffaker at a new FTP, I move back the the prescribed workouts of the plan and I can usually hit them more regularly.
Mills has a peak-and-fade component to each interval that helps you hang in while not compromising the adaptation you’re going after (Chad as posted on Mills before – that’s his opinion, not mine).
Good luck!