I rarely do less than 2:00 intervals.... so won’t comment.

I do lots of 2:00 all the way up to over unders of 18:00. Work:Rest starts out at 1:1 then increases to 3:1 over the course of a 8 week training block.

I think both tolerance to the intensity and ability to clear out the system happens over that time period. On the tolerance side it’s probably half mental and trusting I can hold the power and the other half is physical adaptation. On the clearance side I think it’s mostly adaptation.

Just my thoughts (n=1) no white papers to reference.

Thanks. Anecdotal is fine.

I can agree that with the longer intervals usually I'm closer to 3:1. I usually take a 2min to 3min breather for anything from 3x8 up to 2x20. I usually shorten the 3x8 or 3x10 to 2min after getting used to a power in it. Generally for 1min, I do 1:1. Same for 30/30.

I think the 2min to 4min range is where the suck really lies with "rest". I have had a bad tendency to bite off more than I can chew on completing 3x3min style workouts. I think this time I need to focus on the quality of the work getting done more so than just impressing myself with a new jump in the power I do it at. Those workouts always suck, but you need to actually finish the reps and sets.

I track my CTL in a sheet by zones. And Z4 has gone through the roof. I haven't neglected 5/6, but it's at a more nominal level. Lots of SS and sub/supra threshold work. I'm about to swap the focus, and will be making my plan based on making sure I fully understand what I'm doing and trying to accomplish.

This entire Seiler podcast is worth the listen but rest duration is specifically discussed starting at about 25:00: https://www.scienceofultra.com/podcasts/71

I do this as well. I can pretty much cheat my way through the 2:00 intervals (most I do is 7x), but when I do 5x3:00 3RI there seems to be no hiding.

Having said that, I am not sure what these get me on race day.

I think the over/unders are the most beneficial to my racing. From my training log I can see improvements in these type of sets translate to faster racing. I imagine it is the longer interval with the bursts and recoveries built in that provide specificity.

The shorter the recovery, the more aerobic the work.

So depends on what you want to work on as to whether or not you take shorter or longer rests.

Both at some point is probably best for most people.