Here’s my quote from the Threshold Progression thread. Again, this is my opinion only, so take that for what it’s worth. IMO the preference for threshold training is (1) over/unders (a couple different ways to do those); (2) threshold training at 94-96% of FTP starting point depends on TTE, extending time in zone. Personally, I do a lot (a LOT) more over/under work than long threshold intervals.
And…
Sweet Spot is not as fatiguing as a lot of work, especially for experienced riders, and especially in the 30-60 minute workout range… for some even extending out to 75 min or more. So to run a progression where you spend three workouts trying to get from 45 to 60 min TiZ might be appropriate, but then spending three more workouts going from 3x20 to 1x60 probably isn’t necessary and isn’t forcing much adaptation if you’ve ridden workouts of 60min TiZ previously.
So for experienced riders, I’d advise them to be aggressive with their progressions, and rather than spending three months going from 45 min TiZ to 90 min TiZ and seeking glory intervals of 1x90, spend three weeks getting to 3x30 and then move on to something else… then go back and hit whatever you want to maintain every couple of weeks - maybe 3x30, maybe 3x25, maybe 3x20…
Then if you feel good one of those days, just skip the rest intervals and bang your 90 minutes straight on… but that said, having done a few of these blocks now, it’s a bit of a waste of time to push 1x90 as some kind of arbitrary goal, again IMO. If it is race-specific, you’re a breakaway rider, long TT, long climb, whatever… go for it.
If you’re a Cat 3 crit racer, don’t bother.
“It depends…”