Help Make Sense of my Physiological Chaos!

DIdn’t know where to put this, so I put it here.

During the summer I’ve been doing Z2 work based on MAF HR (unadjusted 122-132bpm; adjusted 112-122bpm). Over the past week I’ve been conducting DIY tests to try and zero in on more precise/accurate levels. Shockingly(?), it seems I may have a very low aerobic threshold (AeT), perhaps ~115bpm.

From the various literature I’ve read:

AeT is a few bpm below VT1 (/~70% HRmax) (Friel)
VT1 is ~the highest intensity that can be sustained for 1-2 hours (ACE)

There seems to be a rather large disconnect between my MAF @132 and AeT @115.

As well, my VT1 is apparently somewhere in the low-mid 120’s…but my “highest intensity that can be sustained for 1-2 hours” is probably higher than MAF HR (I’ve done 5hrs @125bpm).

What’s a doughnut to do??? :man_shrugging:

TIA to all the smarty pants!

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go into a lab and test if you really want numbers… or do what I do, and don’t obsess about it. My all day pace climbing in the mountains is 135bpm, while the talk test / first deep breath is closer to 120bpm. I’ve decided to train knowing that metabolism works on a continuum, varies day to day, and doesn’t operate in strict zones. And so for me, no issues training low aerobic in 120-135bpm HR range.


Can you clarify on the specific question you’re looking to answer? Is it that the relative numbers don’t line up as expected?

I wouldn’t say not to worry about it, but I totally agree that a lab test, or even a multi-day testing protocol with as identical conditions as possible are the way to go for getting precision. Outside of that, I see your issue where defining VT1 is necessary to target the correct zones, but I would add that if you’re below the number you come up with for that, but not WAY below, then I’m fairly sure you’re not going to be far from optimal for any goals that this strategy makes sense for.

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Did you happen to listen to this podcast? It’s based on running but the entire episode is about MAF.

Coach Lucho became so efficient at MAF it became his Threshold.

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Well…I don’t think there is any physiologic difference between what you call MAF and what you cal AeT.

I think of VT1 as ‘first ventilatory threshold’…the point where there is some nominally observable increase in blood lactate. Most riders will be able to sustain VT1 for WAY more than 60 to 120 minutes. If you are riding at a pace you can only sustain for an hour…that’s something physiologically different from VT1.

If I understand you correctly, you’re trying to narrow down a training zone to something less than a 10 bpm band. Even if such a training zone did exist it would be very difficult to maintain during any practical training session. So…you know…don’t spend too much time thinking about it is my advice.


Thanks to all for your input. I guess since I’m not actually training to compete, merely training for fitness, it’s ridiculous to get all neurotic about matchy matchy. Purely for my own sanity and enjoyment, I’m going to stop calling them Zones and start calling them Smears™.

I’ve also been doing VT1/2 and VO2 tests using heart rate variability. Weirdly interesting.
Maybe I’ll blog about it.



Smears made me LOL


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Time to resurrect my weird body thread now that I’ve started “training” again.

Hoping to get an explainer on this:

Last real indoor ride was Sept 22/19. Spent the last 4 months sick and injured and not riding.
This week did one 20min test (~220w FTP) and two dialed down Carson -3’s.

Comparing the last ride with the latest ride:
3hr Z2/MAF @~72% FTP = 195w NP (191w av), 115 HRav
Carson -3 (@88% intensity) ~79% FTP/Z3 = 174w av, 116 HRav

Also compared to an indoor ride when I started MAF training – 3hr Z2 @170w NP (167 av), 115 HRav.
My question is: why am I able to produce the same power:HR after such an extended period of non-activity?

For sure a 3min interval is completely different than a 3hr interval but I was kinda shocked at how little difference the power@HR was given my complete lack of fitness. I don’t know if this is good or bad. :man_shrugging:

Should probs do a 3hr ride and report back.

Looks like you were at 191W average several months ago vs 174W average in recent tests, so a decline. Am I missing something?

Separately, I had ankle surgery a few years back, didn’t train for 4 months, and then only gradually eased back into training. 7 months after surgery I was only 5% slower vs prior year.

I think some people hang onto fitness better than others.

I agree it’s totally a decline, but I was expecting much more than -10% watts at the same HR.

I’ve got ‘The Hour’ scheduled for this weekend so maybe that ride of truth will help reveal some believable numbers. :+1:

From the TR blog:

What is FTP?

Functional Threshold Power is — quite simply — a measure of fitness.

I guess cycling “fitness” could be comprised of components such as cardiorespiratory endurance, strength, and power.

But here I am with 4 months of zero cardio, strength, or power training (aka fitness) and yet my FTP reads in the mid-200’s. In the 'How Fast Are TR Users" thread, this puts me barely on the right side of the bell curve: The Bell curve of cylists - how fast are the average TR users? - #203 by Nate_Pearson

But…if I did a race this weekend I would finish dead last. Got me thinking that there has to be other factors besides “fitness” going into what makes FTP. Any guesses – or actual facts – as to what those other components might be? :man_shrugging:

Thanks for putting up with me! :stuck_out_tongue:

A couple of Qs to help give perspective:

  1. What’s your trained FTP?
  2. How many years have you been training/competing in aerobic sports?

I would think of it even differently than this. FTP is just one component of “fitness” among many. And FTP itself is composed of multiple types of “fitness”.

Meaning: FTP is not derived from one single system; it is the result of multiple factors that is only boiled down into one number for simplicity–using it to drive training is a “one size fits most” and the TR guys acknowledge this and give pointers on how to work around the edges.

There is a definite value in simplifying the complexity but we don’t want to take it too far that direction.

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I don’t have an explanation about the FTP number, but I agree with @devolikewhoa83 where FTP is just one component of “fitness”. I had an FTP not too much lower than where I am now, back when I started structured training. However, there was no way I could stay in a race. I had no capability for repeated hard efforts. I could ride forever, but it basically had to be steady state. I never understood why I was getting dropped because I felt I was pretty fit, but I realized after getting serious about racing that fitness comes in all different forms. I also think there’s a lot to your prior history. Plus, don’t forget some people have “off the couch” crazy-high FTPs. I also thought you were doing some long endurance rides? Or did you stop those completely?

On a separate note, I’m glad that you’re back to training!!


Highest was 305 before I had to stop. Interesting because two consecutive years I’ve hit that level but one year was built on VO2max work and the other built on SS/Thesh work…and there was a very noticeable and distinct difference in that 305w fitness! But this 240-50w FTP? No idea what that’s built upon besides pizza and Netflix! :laughing: :slightly_frowning_face:
Last serious bout of sports was 20-25 years ago in my 20’s, and then again for a year+ in 2018. So nothing crazy.

Did long Z2 rides for 4 months during the summer; at the max I built up to 18-20hrs/week w/5hr rides. But then stopped completely for the last 4 months. So, yeah, fitness – of all types – was really zero (e.g. my resting HR went up 15%!).

I’m thinking perhaps a lot of that FTP is mostly just muscular (and will power!) and mostly not cardio and/or cellular et al. It’s interesting and perhaps something, like most things, you don’t necessarily think about unless it happens to you. I’m combing through the TR blog posts reading their take on ‘what is FTP’.

Yes…? :man_shrugging: Max efforts are still a no go so perhaps I’ll make a good Cat.6 TTer in the fall. :roll_eyes:

Thanks for all your input into my ongoing public experiment!

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You just need to enter different races :joy:

Seriously…why do you think you would finish last? Do you think you couldn’t hold power long enough? Then the answer is, your TTE is low. Can’t jump? Not enough high-end power. Can’t do repeat efforts? There’s your answer.

…at least when it comes to race fitness. Obviously, there is a lot more that goes into racing than just fitness.


Three things driving FTP:

  1. Your VO2max
  2. Your fractional utilization I.e. percent of VO2max that you can ride at for MLSS (influenced by VLaMax)
  3. Your mechanical efficiency at using oxygen to convert fuel into power output

How much the above reduce as you “detrain” varies across people - and probably largely influenced by genetics, and maybe past training history.

I think one thing that is not caught by a traditional FTP test is repeatability. I.e. if you did a few 20min FTP tests one after the other, how would the result change.

I’ve seen studies where VO2max reduces as the rider gets tired. I.e. a VO2max ramp test was done when fresh vs fatigued.

I also think fractional utilization decreases during successive efforts (eg during a race) due to gradually accumulating lactate - and this is more pronounced if you are less trained.

Apparently mechanical efficiency does not vary much, but I think it probably does vary more than people think as muscle fiber composition moves about with long blocks of certain kinds of training. It just hasn’t been measured as much as VO2max and VLaMax, hence it’s harder to identify if it moves around or not.

Another factor in this I think is what your limiter is on performance - oxygen delivery vs oxygen consumption. If your cardio system is your limiter, I think this means your FTP won’t vary as much with training, as, say someone with oxygen consumption (muscle) being their limiter. This one is some speculation on my part, but from what I’ve read, I think muscle mitochondria content and function in the muscle is more trainable than heart performance (stroke volume, max HR) and hematocrit (other than altitude training). I could be completely wrong on this, but Is something I’ve not yet found a study that explores this to set me straight.

Lots of stuff to spend hours researching on Pubmed! :nerd_face:


For instance, my breathing during current Z2 is a lot heavier than when I did the mega block of Z2 in the summer. It’s still conversational but, to me, it’s noticeable aka no-low cardio. In a race, I’d totally be huffing & puffing in no time!

I might win one of those GCN-style eBay bike “races”… :thinking:

This is what initially sparked my questioning. My current theoretically calculated VO2max is ~44, or barely above sedentary level. Started to wonder where the power was coming from?!

Thanks for the effort in your reply, @DaveWh. :+1: As it is, I already spend too much time on PubMed et al. Rabbit, meet holes. :weary:


I had Lamarck+ sched for next weekend for that very reason, but decided to do a Kolie Moore FTP long test. At this point in “training” I think the latter would serve me better as I’m training for fitness and not entering any situations which would require repeatability. Maybe I’ll do both!

Z2 power or Z2 HR?

Z2 power.
HR was MAF/VT1 style.

Caveat being I was riding to HR, power just happened to be Z2.