Sorry, but that’s not correct. On average, the % of VO2max will be lower than the % of HRmax, at least until the two converge at 100%. That’s because at rest we’re at only 5-10% of VO2max, but are already at 20-33% (or more, if you’re chronotropically incompetent) of HRmax.
If you don’t believe me, ask Karvonen.
Tried this protocol for the first time tonight myself. Got through 3x5min, last full one power declined to FTP. Tried the fourth and was under threshold within 3min so I called it.
This was definitely more like VO2max work that I remember from my track days running 800s till I wanted to die, so I “like” it.
TR’s prescribed VO2max workouts never got me to the fish out of water breathing. These did, but it might just be having the power dialed for the longer duration.
All that said, my starts were obviously too hard. I peaked sub-600W so I wasn’t crazy with it, but too hard… probably should be closer to 400-450. Next set I may just start at my optimized interval power for 5min (320W) duration and try to sustain it for the full 4x5 and see if I get the same breathing sensation and RPE, then go from there.
This is my experience too. Shorter intervals results in my legs blowing up and HR never really doing much (touching 90%, but not for any meaningful period). Longer ones (5-6mins) have enabled me to get to 95%+ HRM and maintain above 90% for 2mins+ each interval
Sounds like we had the same track coach…
Have wondered if my own fondness for 2-3 min “VO2” intervals on the bike comes from some sort of mental conditioning from doing those 800M workouts all through high school and college.
I would aim for 1,5 min @ 5’ max power
There’s no way 90s at my 5min MMP would elicit the response I’m looking for. That would be 338W, and I’ve historically done 6x3 min intervals over 340W without much problem.
Try to do 6 minute intervals.
But probably the difference in 5’ power and FTP is quite big (400 vs 300 watt)
My next set will be a hard start around 400W (instead of 600), and max effort from there for 5min, get through 4 of them completely on 5’ recovery. 20min TiZ, and then I’ll scale intervals and rest from there to get at least 4 more workouts at 20min TiZ over the next two weeks.
If that’s not what I want after I try it, I’ll try 4x5@320 (about 114% of FTP) without the hard start.
I think the right combination of “hard start” and “steady interval” varies by person to get the response you are looking for.
And also if intensity changes with successive intervals.
It does take some playing around to find what works best.
For me, 6 equal and steady intervals like Kaiser doesn’t work - meaning The first couple of intervals are easily doable, whereas the last two are “too hard”.
The hard starts I’ve landed on work pretty well. But I’m still tweaking.
I got further in my own version of your Hard Start 6x3 - nearly got to the end of the third interval. 
My HR gets to 90% MHR about 15 seconds before the end of the descending ramp. I’ve not done any VO2max work with intervals over a minute for four months or so, so it’s getting the body back up to speed with them. I’m on a dumb trainer but I think for this type of workout you’d be better turning off ERG mode and just riding at whatever power to keep your HR high enough.
I’ve been listening to a few older podcasts over the last couple of days and there’s one where they are discussing long VO2max intervals with one study doing something very similar to the hard starts of @DaveWh but rather than a level steady state to complete the interval the riders just kept riding at the point where their HR was at or above 90%MHR, one got to 26 minutes 
I agree - I definitely felt more of the stimulus I’m used to with vo2max work last season when I did 4x6min steady power intervals vs. the typical shorter intervals in most of TRs plans. This is also the first time I’ve done block-style periodization along with the hard-start, power-fading intervals, so I’m keen to see how it works.
My next problem to solve is how to recover from this block. Adaptation takes about six weeks, so rather than diving into more FTP work, I’m looking at more HVLI where I do a lot of zone 2 riding with a maintenance session every two weeks, and probably executing a four-week block of that before more SST/FTP work.
Just did my first set of hard start intervals.
6 x 2.5 min.
My heart rate only peaks into the last minute,
96%
95.5%
95.5%
94.4%
94.4%
92.6%
of maximum heart rate. To me this represents cardiac fatigue., or severe enough leg fatigue that the power I’m able to keep my cadence above 110 is too low to elicit a cardiac response.
For me the intervals were done best with no erg mode and following more of the empirical cycling model of structuring these. I just finished a full block of the Vo2 max, and gave up with erg mode after 2 of them.
All the tweaking is done with my own all-out effort, and the erg mode (even when manually adjusted) either left me pushing too hard or not hard enough.
You may be right here. HR isn’t everything but it’s still quite important. IMO this suggests you went too hard on the first couple… Just from my experience and talking with a few people much smarter than me about it
Maybe the hard start is too hard? I know if I go out too hard in the first interval, my performance on subsequent intervals suffers
Definitely not cardiac fatigue.
Also, 2.5 minutes isn’t really long enough for a VO2max interval. Basically you’re stopping just when things are getting good.
These were done in “standard” mode on a '17 Kickr. Also agree pretty short for VO2 max intervals, mostly a test of concept and my first venture not in erg mode. Agree with the hard starts probably too hard. I struggled with Spencer last week, and VO2 max is one of my biggest weaknesses at age 67. Will give 3 min intervals a go tomorrow.
How did you get to this 6 weeks number?
I asked a question about this once, but apparently:
Adaption starts with the first session and
The muscles of the heart change twice as fast as other muscles and remodel on average every two weeks (from memory it was two weeks)
…so you might not need six weeks.
I don’t plan on taking six full weeks of recovery or HVLI time. I’ve been planning week to week so I’m guessing 1-3 weeks of HVLI after the VO2max block, followed by some testing and another progression of SST at my higher FTP.
I didn’t. I should’ve said “if”. But both the TR podcast and Kolie Moore’s podcast have referenced about six weeks for the body to fully adapt to VO2max work. Kolie talked about allowing yourself to “fully recover” from a VO2max block.
I could interpret that as it taking six weeks to recover, but I don’t think that’s true at all. Instead, I’ll go with a standard recovery week, then probably do another baseline test week, then into 1-3 weeks of HVLI before another more intensive base period.