We don’t even all agree on what FTP is or how to measure it!
For an analogy, consider how diverse approaches are to nutrition, weight maintenance, blood sugar control, and other issues that have huge bodies of research, solid funding, and decades of advancements.
Crux of the matter is that at some point, you need to buy into a particular set of assumptions and work from there.
I think iLevels were actually developed by Coggan to deal with the fact that work above threshold is not a standard percent of threshold. That’s what I vaguely recall from the 2ed of his book.
I think the reason why there aren’t standardized “levels” even below threshold is that there aren’t sudden physiological changes in your body at different percentages below FTP. It’s like how the sky transitions from blue to orange during a sunset, not like a rainbow or a set of stairs.
Likely the first thing he’ll say is that they aren’t prescriptions. The zones are approximate descriptions only. And they don’t tell you how to train. Rather, they are useful when trying to communicate training done / to do.
Your body is not digital. There are no hard limits between any zones. The zones are merely meant to describe fuzzy areas that have no exact edges.
It’s better to think of it like the color spectrum. We’re can agree that the colors yellow and orange exist, but where is the exact line between them? Somebody could define an exact dividing line, but it would not be completely scientific since even the definitions of pure yellow and pure orange are arbitrary.
Internet debates would have been greatly reduced if the zones were originally defined as overlapping. Then it would be more apparent that it’s not rigid.
Training wise, it doesn’t matter if you ride at the supposed top of Z2 or the supposed bottom of Z3, the training adaptations +/- 10 W will be indistinguishable.
The only time it really matters that much is right near FTP, where 10 W too high is a lot more fatiguing than 10 W too low, even though the adaptations aren’t much different. Thus the anchoring of zones based on FTP and the recommendation to err on the low side with your threshold training.
You should search this forum. Your questions are nothing new and all this stuff has been discussed to death.
You can even search the Cog’s posts specifically.
There are articles on Training Peaks written by Coggan, but IIRC, some of them have some editorializing by TP staff that Coggan doesn’t fully agree with. Though he’s clarified those cases here so again do some searching.
Here’s how to search a user’s posts:
Find a post by the user, click their username.
This pops up a box with their profile picture and a few stats. Click the username in this box.
You are now on their profile page. Click the magnifying glass at the top of the screen.
In the search box there’s a checkbox for “search posts by (username)” that you can check.
If you use the various features of the search you can find lots of good info.
I’m guessing you are truly trying to be helpful. And maybe I could have already stated that I spend a lot of time here and on other forums. I also know how to use the internet and have read lots of content.
I also know we have a smart and well informed group here - including Andy Coggan himself to provide context. So thought I would surface this as a discussion. There are also plenty of folks like me who are still new to cycling but love it and want to understand more.
If you want to debate the merits of 3 vs 7 zones, or which FTP determination method to use, again it’s been discussed to death and you posed no specific questions. Better to post in one of the existing threads and build off one of those discussions.
maybe I could have already stated that I spend a lot of time here and on other forums.
Yes, we have no idea what you know or where you’ve already looked without you stating it. In the absence of that, suggestions we offer are useful since everyone comes into these with different history. Unstated assumptions are unknowns until you share them.
Please look closely at what I asked or maybe ask for clarification.
I read his book, looked at the article you posted here and have followed the other thread where there is healthy debate/discussion in the ISM Zone 2 thread and have been coached, have multiple devices and spent (like all of us) hundreds of hours trying to learn.
Then I don’t understand why you posted a question that has been asked and answered tens of thousands of times?
Your tone is coming across a bit condescending. Let me help you. I am not asking about his training levels. I know what they are. And unless any of us others on here are PhDs in physiology then none of us are experts.
I am simply asking why there is no standard or why one can’t be adopted. And why Coggan’s levels are butchered across at least 2 different platforms.
If you have another article or post here about the standardization of zones and levels or what conferences or meetings have taken place with physios or manufacturers, I would love to know.
We’re talking about physiology, not mechanical design. Nobody is going to write an ISO standard for the definition of FTP or training zones.
The best you’ll get are peer reviewed articles describing a specific approach, but we already have those in some cases (Critical Power Model for example). But most lay people aren’t going to wade through and comprehend all that.
Second best is someone like Coggan laying it out in plain speak for us (see the previous two links I gave). So we already have that as well.
So we do have standards. What other form of standard are you wanting?
If you’re asking why are there multiple competing models, there’s several reasons. First of all, even in science there’s always competing theories. The majority of scientists might agree that a particular theory is correct given what we know today, but that’s why science exists, to learn what we’re doing already know, which might prove those theories incomplete (Newtonian Physics vs Relativity).
And when it comes to lay person definitions, well that’s partially marketing at work (Sufferfest 4D fitness is just Coggan’s power profile chart) and partially human nature. I refer you to this famous XKCD comic.