Cycling Fitness / Training Advice

There was some stuff by Seiler that showed what you're proposing had great effect, going from longer to shorter intervals. I can't think were I saw it right now.

I like to think about it in total work done. Which is time duration and effort level. If you go to hard, you can't do so much, but go too low and it's not a potent stimulus.

I have found 4x10min to be good. It's a good amount of work (done 1 or 2x/week) and hard but not super hard. If I do 4-6x4 then i need more time to recover.

Also due to my genetics, I really do not need to work Vo2 directly, I can do 5.5L/min. So I focus on improving efficiency etc. The more time I can accrue riding my bike at around 70% MHR the better I will be. That said if I needed to repeat 3-5 min efforts, then I would work it, but I don't.

That said, I have given up most structured training now. The simple fact is it does not make much difference. Years back I followed a rigid programme, with all sorts. Last year I just did whatever I felt like. My power numbers were better than ever last year.

8x4 at that sort of power with 90sec recovery is solid work. But not over the top hard. Not surprising it works. It's not far of my 4x10 efforts.

Thankfully I have chosen a division of cycling that does not reward finding the final 5%. But rewards being stubborn.