Z2 increase vs FTP increase

After a block of training which raises FTP, is there a “normal” amount which Z2 power (e.g. power at VT/LT1, MAF HR, etc., whatever you want to label it) will increase?

I’m not quite sure I understand your question: within Coggan’s 6/7 zone model, Z2 spans 56–75 % of your FTP. Thus, your Z2 power by definition scales linearly with your FTP. But I infer from the way you ask the question about your Z2 endurance, correct?

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Are your referring to Polarized zones? If so Zone 2 is basically FTP and Zone 1 is VT1/LT1. And haven’t seen correlation that says x% of Z2.

And as far as I understand, in a three-zone model, Z2 is often split into Z2 lower and Z2 upper, which roughly correspond to Coggan’s Z3 and Z4.

Ha! Yeah, re-reading it now, it’s confusingly worded.

Better to use a 3 Zone model. Is it possible to push your Aerobic Threshold closer to your Anaerobic Threshold by more than what your FTP increased? (e.g. my FTP bumps up 5% but my AT rises 20%)?

Image for illustration purposes only:

Edit: from listening to a lot of MAF stuff, athletes can push their AT very close to AnT/FTP, so it’s a combo of HR and watts to figure it out.


That helps, thanks. A similar question is whether you can raise your FTP by learning to ride closer to your VO2max. As far as I can tell, the answer to both questions is a clear maybe.

I’d approach the topic from the vantage point of one of the training principles, specificity. Your training should have a purpose, and that isn’t “riding at a higher percentage of FTP”, the latter is a means to an end.

Specifically, does your type of riding require you to get better at riding sub threshold for long amounts of time? If the answer is yes, then you can either approach it by trying to ride a higher percentage of your FTP (which is what you asked in your first post). Or you could simply raise your FTP. In reality, you’d find a compromise between the two with different emphases.

I don’t think there is a definitive answer as to which one is better, it depends on the athlete, your theoretical limit, your current level, etc. For example, if you are relatively untrained, I’d put more emphasis on raising your FTP. If you think that increases in FTP are hard to come by, I’d put more emphasis on building your aerobic base. Training time is also an issue: I’d love to spend one day per weekend in the saddle, which is a perfect way to build my aerobic base. But that’s not in the cards for at least another 5-10 years.

Is the question if LT1 and LT2 are linked by a fixed amount? I’d think no. But on the other hand, usually when you improve one aspect of your fitness, others will improve too, so it’d be normal to see both move at the same time.

Thanks for the replies and thoughts.

Some context: recently finished a 3-week VO2max block (Aug 1); FTP increased by 5%. However, after a rest week, the first thing I noticed was my AT was up by maybe 10%.

But now, 3 weeks after the block, I’m finding my AT has increased by perhaps as much as 25% (in watts; comparing pre-block and historical data).

Pre-block AT: 75% FTP
Post-block AT: 85% FTP

Could the VO2 work have provided that much bottom-end stimulus? Or is it a case of AT is easier to move than AnT (is easier to move than VO2max)?

Looking at it now, I’m thinking my AT was just relatively untrained and responded more strongly to the training with a larger move.

edit — from Scientific Triathlon:
“Option two is to “drag” your [aerobic] threshold further to the right on the lactate curve by elevating your VO2max as high as possible, hoping that the points below the VO2max will fall into line.“

I would think the answer is yes. See this chart from coggans book

Not sure that is directly applicable but I believe I’ve found my answer. Just had to talk it out!

Yea, KM answered that on instagram once. He’s got an athlete that is up to 75%

Uh…so what does 85% mean?! :scream:

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yea read that after posting. are you a robot?

When say 85% what do you mean? like thats your ride all day pace?

Aerobic Threshold/VT1 (determined by various methods; historically reliable @ ~73% HRmax) is currently sitting at ~85% FTP wattage.

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Impressive! Expect a call from a World Tour team to pull the peloton all day then! Of course your FTP must be around 400w, but that’s a minor detail :joy:

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As stated above, one of the popular MAF proponents (a runner) mentioned he once got his aerobic threshold very close to his anaerobic threshold. There’s probably a ton of tri people who are the same.

Nothing to do with a sky high FTP or monster watts so even you could do it. :+1:


Keeping the shortcomings of testing methods in mind, I saw a greater increase in my estimated aerobic threshold compared to my FTP after a solid year of training. AT increased by around 40W (225-265) according to a blood test while FTP increased by about 15W (285-300). FTP increased by about 5-10W (300-305) according to ramp tests.

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IMHO there is a lot of N = 1 anecdata out there. I think whether you are able to do this depends in no small part on your physiology, your current training status and lots of other factors. Don’t get me wrong, it is a viable option IMHO, but you should not expect it to necessarily work. The cards can get mixed fresh, too, when things change. So for example, the relative increase in your AT could also be an indication that physiologically you could raise your FTP with the right training. Once you raise your FTP, your AT power might stay roughly the same, but is now a lower percentage of your raised FTP.

Personally, my strategy (i. e. my N = 1 anecdata) is that my body responds well to both, and I try to alternate where one year I focus on raising my FTP and another year I try to increase my endurance. This year I have raised my FTP quite a bit, but I have become much more sensitive to e. g. not sleeping enough and other factors. Workouts that I find challenging are also harder on my body, and I need to be more careful with managing fatigue. That’s fine, next year I’ll sprinkle in more Z2 work. I’ll have a new toddler by then anyway and I don’t think I’ll be able to dig as deep as I do now.

PS One more thing about AT: AT makes very good suggestions, although they lean more on the conservative side. Usually it is I who causes problems when I override AT’s recommendations and use an alternate workout that is a tad too hard.

I don’t think I’d use heart rate to estimate my ventilatory threshold 1, especially not some fixed number. In my experience there is tons of variability, my VT1 (and heart rate) are very sensitive to fatigue, for example, both long-term fatigue and short-term fatigue.

I’d think all work done under your aerobic threshold is also aerobic. So the “aerobic threshold” is where the system starts to become a little bit overloaded, and there’s a notable rise in blood lactate. But if you do a lot of aerobic work to improve your top end aerobic capacity, surely it will also affect when the low end becomes noticably strained.

I do wonder if it’s to do with central and peripheral adaptions - AT1 is where the central system kicks in to take some of the load? AT2 is where it gets maxed out?

That would match with the MAF story - tons of peripheral work, but no high central load.

Maybe? :man_shrugging:t2: This is all following a VO2max block (with focus on remodelling the heart), so perhaps the adaptations are starting to show.