DancenMacabre said:...I mentioned stagnating a short while back & that was a period with lots of tempo riding. I did find that the more tempo rides I do, the easier tempo rides get + CTL goes way up. When I do more 2/3 x 20's then I find those easier & FTP progress quicker. Specificity maybe?...
I think you're looking for improvement on too short a time scale. Sustainable power for 20 or 30 minute intervals can vary from day to day and week to week for a lot of reasons including freshness, motivation, nutrition, hydration, even weather conditions. Just because 20 or 30 minute power increases, decreases or stays the same for one or a couple of workouts it doesn't mean that FTP has measurably changed.
Yeah, progress is rapid at the start in part because it takes most folks a while to learn to do longer steady efforts near threshold and some adaptations like increases in heart stroke volume are quite rapid at the beginning. But noticeable increases in fitness follow predictable time courses on the order of 6 or more weeks to adapt to an increased training load.
Trying to track FTP progress or lack thereof and modifying training on time frames much less than 5 or 6 weeks is basically an exercise in chasing the noise at least for someone past their first couple of months of training.
I'm not arguing your preference for keeping at least some L4 in your schedule, I'd do the same thing. It's just that these things take time and although you can minimize that time with smart training you can't really speed up the rate at which cells are regenerated or large scale adaptations occur and time frames for the large scale adaptations are measured in months, not days or weeks.
Anyway I wouldn't judge the success or failure of any particular training approach grounded in good exercise physiology in just a few weeks. Three weeks without a noticeable change in FTP doesn't mean it's time to change training strategies and a few weeks where numbers seemed to go up with focused L4 training doesn't mean it's the best solution (e.g. it might just mean you see increases in 20 minute power because you're doing a lot of 20 minute efforts).
I'm not knocking anything about your training approach, just pointing out that it's easy to jump to conclusions if you don't take the long view on this stuff and that's led an awful lot of cyclists to scrap good sustainable training in hopes of quick fixes when the results don't seem to come fast enough. So it might not be a question of specificity as much as a question on patience....
-Dave