Thanks for your suggestions and answers, @Joe and @devolikewhoa ! Workouts I recently did and could not complete: There Is No Try, Joy Ride, 14 Vise Grips, Nine Hammers (ok, that one is no surprise).
I used to be able to complete e.g. 14 Vise Grips before doing the FF (coming from a 12 week general road cycling plan).
It’s only the longer intervals I’m failing.
Which workouts I’m doing doesn’t matter that much, generally speaking if it’s yellow and longer than 2 minutes, I’m not able to complete it.
The target power typically is right at or around my MAP result from FF (318). For comparison, my AC is 479. So, it is significantly lower.
What makes me suspicious is that going for 1:30 or 2 minutes is quite “near” the target duration for AC efforts, and I’m not fading away (like what is common during more “FTP-style” intervals), but really failing from one moment to the other. It doesn’t really matter when during the overall workout the interval happens (I do recover very well).
So, to me, it looks a bit like my AC system is doing most of the work at the beginning of the interval, and since it’s not pushed to its limit, it can hold on a bit longer, but once the aerobic system needs to take over, it just fails for whatever reason.
It’s an oversimplification for sure, but VO2Max is my weak spot (always has been) and I really need to train it, and not doing half-hearted AC intervals …