Originally Posted by
billridesbikes
If the duration was longer you wouldn’t change the spread for power but instead you would lower your target power inline with that duration, this is what would give you the best time.
I should have been more clear. Duration refers to duration of a particular ramp (as opposed to duration of the overall climb).
Imagine doing a 30-min long workout alternating btwn over/under of 7.5 minutes each, and one where the over/under is 3 minutes each. One could get away with slightly greater delta in the latter situation (and thus higher intensity during the over section), whereas holding the same intensity to 7.5 minutes may lead to failure 2/3 of the way through the workout. One could target VO2 max intensity for the 3 min ramps (say 112%) and recover at 88%, but such a spread would be unwise if duration of the over section is 7.5 minutes.
The other thing to clarify is that if truly all out, the average power sustainable over a set period is always the highest when performed in an even manner (at the critical power for that duration). Any over/under would lower that average power sustainable for that period (b/c lactate generation isn't linear with respect to intensity). The only reason why over/under is optimal in the first place is due to gradient differences.