Since I gave some descriptions recently, I'll respond.
nmcgann said:From other people's description of TTing that doesn't sound normal (whatever normal is 😉). Can people generally do a 5min VO2max interval straight after a 20min threshold interval?
No way. Maybe, just maybe, under the right level of rest, at the end of a 20 minute interval, I might be able to squeeze out 1 minute solidly in VO2-land at the end. More likely something less. I just did one hour at ~93% the other day and barely managed the last minute at about 5% above where I was riding before that (not 5% above FTP).
nmcgann said:Is it a function of what % of FTP the threshold interval was at? (i.e. 95% - maybe, 105% - no way)
For sure. The higher the intensity you are riding at, the less reserve you have "in the tank" for the end. That's why when I do 1 hour "bursty" @ FTP (by NP) on hilly terrain (drilling it up hills) to simulate a hard race, I have to back off the average effort so that the average power is at least low L4 or high L3. I need the headroom otherwise the hard efforts up hills will be blunted. The same thing goes for the end of a TT or interval.
I think that interval duration has a similar effect too.