Hard FTP intervals - impact on VO2max?

With no races around I find it quite motivating to do climbs of 20-40’ at a very hard pace, kind of QOM-chasing style.

My HR and breathing are naturally very high during these efforts. Actually I accumulate more time at >90% HRmax doing my favorite 32’ climb all-out than during my classical 4x8’ VO2max intervals.

Q: From a physiological point of view, can efforts like this (2x25’ FTP, 1x30-40’ all-out etc.) substitute standard VO2max sessions? (Obviously RPE is higher but motivation is higher too.)

[I’m very well-trained with several years of structured training; just to say that I’m not in the “whatever-you-do-will-make-you-faster” part of the population :wink: .]

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I think that it would depend on whether you are reaching a high heart rate as a result of a high cardiac output (normal SV), or simply due to cardiac drift (reduced SV).

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Simple answer for well-trained people like yourself:

  • If you are under FTP, it’s not really affecting your VO2 max and you will fatigue before reaching VO2max
  • If you are over FTP, you will eventually reach VO2 max if the power is held long enough* (edit: see post below from epiricalcycling)

From what you posted, there is really no way to tell whether or not those workouts did or did not substitute for VO2 max, but what I can say is that the fatigue tradeoff for the VO2 stimulation is probably not worth it for intervals of that length if that was your goal.

Doesn’t mean it’s not still fun though :slight_smile:


Ditto. My n=1 from just the last week is that all-out VO2max-length K/QOM segments contribute to fatigue far more than a standard controlled VO2max session. If you are using the segment for actual VO2max interval training, you’ll be going a lot slower than anaerobic ‘all-out’ and won’t be contesting the QOM.

This. Sometimes you just gotta go out and smash it for mental health!

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Hm, but I don’t need to be at VO2max to stimulate VO2max improvement, right? I mean usually people assume that time spent at >90% VO2max is a good indicator of the effectiveness in terms of VO2max training stimulus.

I don’t have any lab data, VO2max values etc. My best 5’ power is 335w, my 32’ all-out 273w, my standard 4x8’ (2’ recovery) would be 280-285w. I’m using words I don’t know much of, but does the VO2 slow component of the long 32’ effort compensate for the reduced power output?

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Depends :wink:

Whats your FTP?

32’ (273w) is the longest I’ve gone all-out recently. I’d estimate I can hold 265w for an hour.


Good luck trying to fit your bike down this rabbit hole! :laughing:


Given that, if you were over threshold and felt like you were for that duration, then you probably got some VO2 stimulation.

However, the real question is whether it was actually enough to induce adaptation and super-compensation. Depends on your state of training and how much work you’ve done in that area recently.

If you were coming out of base with no VO2 work, probably a decent amount!
If you just came off a VO2 block, probably minimal to none.

TLDR: If you want to get VO2max gains, long threshold style intervals aren’t a very efficient way of going about it.

I came to this thinking “vo2 slow!!!” and that podcast.

I listened to that podcast over 3 nights in bed before going to sleep, so my history-graduate scientific interpretation will be sketchy at best. But from what I remember, the main conclusion was that it’s very very possible for heart rate to go up in a long interval due to muscle fatigue, whilst being nowhere near vo2 max, right?

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Ok thanks for your input!
Well I haven’t been doing a huge VO2max block. I’m kind of rotating between VO2max block - SST/tempo block - endurance block.
Being based in Switzerland and with some nice w/kg it’s tempting to throw in some all-out climbs :wink: .

Hm I’m starting to realize that my question is a bit dumb given that due to my lack of knowledge of my physiological parameters I don’t even know if I should target VO2max to improve my overall performance…

Perhaps asked differently, in what framework would hard FTP intervals make sense (let’s say 2x20’ slightly above FTP)?

2x20 slightly above FTP would benefit your FTP, but you would incur significantly more fatigue for the benefit compared to 2x20 slightly below FTP.

This is a totally made up estimation, but I’d say for you, 2x20 @ 255w would be better for your FTP and cost you 30% less fatigue. You could probably do 4x20 @ 250-255w for the same physiological and recovery cost of 2x20 @ 275w and the 4x20 would be way better for your fitness.

(edit: disclaimer that I am not a coach just a regular guy with an evolving understanding of the training science)


Thanks, that’s actually a very interesting alternative approach. Instead of substituting my VO2max intervals by “slightly above FTP stuff” I’d then rather substitute some of the sessions in my SST block by “slightly below FTP stuff”.

[Usually I don’t have a problem with intensity discipline, I was just getting a bit crazy due to the lack of races…]

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for my penny’s worth. whatever your choice of % above ftp and duration, its all dependant on how it fits in with the rest of your training over many weeks. only then will you know how well its worked. just do lots of consistent hard work.

Although some people seem to like to push this claim, it isn’t true. Only if you are enough above FTP, but not too far above FTP, will you reach VO2max. Below or above that range, fatigue will occur first.

This recent study illustrates the above perfectly.


Anna, it depends what your vo2max limiters are. We can look into the published lit and find many instances of vo2max increasing with ftp training. But there aren’t any studies I’m aware of looking at just this over the course of years. So in your instance as a well trained person I would say no, those workouts won’t improve your vo2max. You are probably limited on the “delivery” side by heart stroke volume, and if your volume is low you might similarly be limited on the “uptake” side.

Some will say that more time around 90-95% of vo2max is a better stimulus than less time at 100% but I find the opposite to be true. So sort of like what Steve was saying, if you hold just about any watts over FTP long enough you’ll probably hit 100%, but what he forgot to asterisk is that it’s likely you’ll fatigue before getting that high. I typically don’t assign vo2max intervals any longer than 7, mmmmaybe 8 minutes depending on the athlete, and with some we’ll only go as long as 4 or 5. So as much as doing vo2max stuff sucks, it is necessary to train it very, very directly.


I presume we’re talking %s of physiological vo2max here, and not the nebulous and possibly mythical “vo2 power”?

I’d always kind of assumed that 100% vo2 max was something only seen at the end of a ramp test or maybe the very end of the final vo2 interval before you collapse.

100% vo2max (the power is indeed nebulous and variegated) can be seen very frequently doing max intervals of about 20-60 seconds long (depending on anaerobic capacity). It doesn’t have a “fingerprint”, as Coggan might put it, on the power curve or on some other thing we can track during exercise like breathing. My practical guideline is just if you’re breathing as hard as you can, which of course can be somewhat subjective, but when you get there, it’s fairly obvious, though different from the other coaching cues I use with breathing of “labored but steady” and perhaps even “ragged”.


Interesting. I’ve been gradually moving into the opposite direction, for a couple of reasons

  1. Main reason: I had read the “spend time at >90% VO2max” thing too often. E.g. thinking of Seiler’s classic study comparing 4x4, 4x8, 4x16. Perhaps 4x4 gets one close to breathing-as-hard-as-possible (but was judged inferior to 4x8 in terms of training adaptations). Definitely 1x4 all-out would have me end up breathing as hard as I can but then I don’t even get to 4x4 because my brain and legs would likely refuse after a true all-out. Have never tried it though.

  2. With short VO2max intervals I was afraid of getting too much into anaerobic terrain and increase VLamax.

[3. Personal preference: I am a diesel and prefer the pain slowly creeping up instead of hitting full throttle right from the start.]