Is it the time “around” VO2max, or how close you actually get to 100% of it that really matters?
I ask because I see lots of workouts designed to maximize time around VO2max, but I don’t know of any data to actually show that that matters.
Related: does it matter if you get to VO2max by drifting up to it, or are adaptations maximized by hitting VO2max at a higher HR and lower SV?
You want to be maxed out for as long as possible. The answer for VO2 intervals is… go harder.
Aren’t those two somewhat contradictory? I mean, if I go as hard as possible, I won’t be able to go as long as possible. So which is more important?
Guess you need to train more. 
Nah, the days of chasing the $12k dream are now behind me. I did get to see parts of the world I wouldn’t have otherwise, though.
Yup, this is still the question.
Maximizing time near VO2max is commonly referred to as optimal for eliciting improvements to VO2max, but the correlation is far from fully mechanistically established.
Here’s one reference chain back to 1986.
(Read this review first, if any. For a comprehensive review of HIIT training methodology & physiology)
I’m not satisfied with this conclusion though. There are very possible mechanistic pathways downstream from systemic VO2 that may be more related to cell signalling & adaptations (which I don’t know enough about to speculate too far just yet).
Whatever the case, most likely improving your own VO2max will require improving your specific limiter to VO2max. That might be peripheral somewhere in the muscle fibers, or central cardiovascular structure/hemodynamics. Traditionally it’s thought most athletes are central (O2 delivery) limited, hence the empirical relationship btwn time near-VO2max and improvements to VO2max.
All that being said, I don’t think work-matched intervals scattered within a longer ride would be better than the same intervals done sequentially. But maybe if the scattered intervals allowed you to go harder and/or longer, ie. higher total work vs iso-effort (same RPE) intervals done sequentially?
I recall reading somewhere that it was the other way around - that most athletes were limited by O2 uptake, as opposed to O2 delivery 
That said, I’m reasonably sure for me I’m limited by O2 delivery, as during above-threshold intervals, my cardio system is what constrains me (the “I think I might die” feeling), and not my legs getting tired.
And to improve O2 delivery, makes sense that sequential intervals would be better.
To your point I think there is more nuance currently being investigated, but I think the prevailing view is cardiac output generally limits VO2max. [edit] However VO2max doesn’t necessarily limit performance.
From a very recent review by Dr. Michael Joyner
i would say both, structured with the appropriate rest for the stimulus.
spaced out for event specificity or like Brendan said, doing them with several KJ in the legs to simulate race conditions
I’ve personally found that going REAL hard on the ‘warm up’ intervals to get breathing and HR up to V02 levels (for arguments sake let’s say HR at 90% max for ball park).
Then during the proper work intervals I find breathing and HR get to V02 state much faster, even from first interval.
Thanks for the reply. Seems like my questions are still almost completely unanswered.
Aren’t most of life’s greatest questions left unanswered?
Do some homework and find the answer for yourself.
I thought you had me on ignore?
It’s not a power target it’s a physiological one. You want to tap out your anaerobic system as fast as possible then drive as hard as you can for the rest of the duration. Your power will sag. That means you are going hard enough. You just don’t want to blow up to where you can’t get over threshold anymore.
Here’s a 4x5 I did:
So I think the crux of your question is how does rest intervals effect my workout. The guys over at FastTalk did a whole podcast about this and its pretty informative. It goes into the science and physiology of what your body is doing.
I’ve looked at that before…was your FTP accurate?
Maybe all my polarized work has weakened my quads but I doubt I could average 135% for 5min. Even your last interval was at 122%. Last 5min session I did worked out to be ~112% av but still hitting HR targets. 
135% for 5 minutes 
. I can do roughly 125% and I know that’s pretty solid. That’s for one effort though!
FTP 321, 5 minute power 400w.
That answer doesn’t seem to be directed at my questions?
I tested at 230 a couple weeks later and the model has me at 240 right now with ~65 minute TTE. I haven’t attempted an FTP test for awhile though. The shape of the curve is more relevant than the height of it relative to the stated FTP.
Aren’t those two somewhat contradictory?
No.
I mean, if I go as hard as possible, I won’t be able to go as long as possible. So which is more important?
You need to go hard enough that your anaerobic system can’t contribute to the the effort in a meaningful way. After that you go as hard as you can.
