Everyone is a bit different in how they respond to different training intensities.
This year has reminded me that I tend to see the most adaptations from 1) high zone 2 volume to build as big of a base as possible 2) sweet spot – 60-120min sustained “chunks” of 90-94% and 3) 4-10 minute zone 5 intervals.
For whatever reason – and even though I’m a TT’er by type – 95-100% FTP intervals don’t seem to give me as much FTP benefit over a 6-8 week period as those long 90% chunk rides.
For me, a lot of SST and then a little Zone 5 seems to be the best formula.
What have you found works best for you?