You more expert folks have any rationale or favorite %'s for under/over intervals? I'm using some of the Zwift ones that originate from more legitimate sources and athletes. However don't understand that aspect.
One goes at like 95% then 105% at 2:1 ratio which seems very classic. Another two go barely Z4 for the "under" but give you a lot higher "over". One of them gives you like 120% for 30sec another gives you like 150% for 15sec.
For those that go "way" over, what's that doing? Is the classic one better or do those other two also serve a good purpose to tickle up ftp in the progression of workouts?