Iñigo San Millán training model

Assume this has been mentioned in one of the 960 posts in this thread, but I’ll ask anyway. I understand that finding VT1/LT1 w/o being lab tested or doing an INSCYD test can be between 70-80% of HRmax for most. It can also be different, I get that. But for those who don’t have access to a lab test we can figure 70-80% right?

Onto my question:

As one gets fitter, how do we account for that increase in fitness with regards to where our HR @ VT1/LT1 goes?

Today I do a VT1/LT1 endurance ride and my goal is keeping my HR within a range of 136-144 BPM and hope that my power falls around 175-195w (FTP is ~310w). I typically see this HR range coincide with this wattage range.

I know that my wattage @ VT1/LT1 will increase as I become fitter, but what happens to my heart rate @ VT1/LT1 as I gain fitness? Does it move in lockstep with the increase in watts?


I think once you are fairly well trained, your hr at LT1 should stay fairly consistent as you get fitter. So if you improve LT1 from 275w to 300w, you should have HR of 145bpm in both situations: ie, your body is working similarly hard for a greater power output.

likewise, you could also see a HR decrease at a certain power output, so 250w might go from 140bpm to 135pbm.

Interesting. But with threshold HR (LTHR) can actually increase as the watts at threshold increase. I do wonder if it’s the same at VT1/LT1.

good point. that was my understanding, and lines up well with my experience of improving LT1 anyway.

anecdotally if you look at McNulty’s strava (one of ISMs athletes), you can see he is cruising around at 130/135bpm at 280w or so. but he can still reach high HRs during efforts at or over FTP

I have lab data for many years. LT1 HR is pretty much the same throughout. Wattage changes. I even have some data from 25 years ago, LT1 HR (as I would define it these days) is pretty much the same. Max HR goes down, though.


That’s interesting. So, it’s constant, even though Max HR degrades with age.

:+1: Thank you

I’m just guessing based on feel. FWIW, my MAP is ~430w @ 3min, but FTP has trended down the last couple of months.

Steve Neal has a good explanation of how he prescribes LT1 rides on the–cough Fast Talk cough–forum in a great ISM thread, and was talking to a user there whose FTP is close to mine and was advising he stay under 200w. So, I give myself a range of 175w (really easy Z2, maybe high Z1) to 195w (medio Z2) thinking this could be a good range. Generally, I ride closer to the 200w number.

Today I did 100min @ 201w average power with an average HR of 139 BPM. My VT1/LT1 range could likely go a little higher.

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In this AMA on Zone 2, Peter Attia seems to be mostly using ISM’s principles. He describes it as low Z3 in a classic 5-zone model.

Anecdotally, I did my share of “ISM Z2” this winter based on the information shared in this thread. I set the intensity right at the limit of where I started to “feel” something in my legs. That happened to put me right around 75% of both FTP (215 / 285) and max HR (130 / 170).

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And what about “summer HR” I have about 10-15 beats higher HR at the same power output in summer (higher temperature). Do I still need to focus on HR? My HR max is 195 and I’m trying to be around 140 on my endurance rides…

I have lactate data going back two years and power data going back four years (so not in same league as sryke lol ), my LT1 HR has been 128-130bpm the whole time.

You mention Steve, if you ask on “that other forum”, he has a little protocol you can use to get LT1 without using lactate, based on breath count (NOT talk test). Not sure if he will explain it outside of a consult though.

Whereas my LT1 HR has remained constant, my HR at balance point has gone up with fitness, which is expected. That’s not an ISM concept, but something I also use in concert with LT1 measure.


For the German speakers very interesting analysis of the San Millan’s publication including UAE team and Pogacar’s data (presumably). Some English also included.


I just scrubbed through the video and there is definitely also plenty of English to make it worth a look for us Yanks. Thanks @Skeggis


FWIW, you can turn on Closed Captioning with auto-translate in Youtube.

I am always a bit puzzled by TCC/PA videos. They are trying so hard… Somehow they tend to replicate the same formal errors, over and over again. These are reintroducing 1980s textbook wisdom and drawing wrong conclusions. E.g. introducing lactate levels of 4mmol as some kind of threshold. As it might hold true for a population average it does not on the individual level. And again: is his conclusion really “train slow”? He just demonstrated himself that Tadej Pogacars AeT will be approx. 300w. ISMs recommendation is training at/around AeT. Slow? I really want to be that slow…

Not sure if I got that impression from the video. More like that they just took the 4mmol as a reference for the discussion, otherwise its difficult to compare…Same for the training conclusions, I think ISM also himself was just quoting many older studies stating the obvious, going “slow” is good for endurance…

I struggled to watch the beginning of the video even with subtitles. Can someone give me the management version? Is he trying to prove that Pogacar’s performances are unreal? What is the conclusion?

The conclusion concerning Pogacar is that his performance is reasonable. At least if it is his data that is presented in ISMs 2020 paper (and Pogacar is the athlete with the astonishingly low la-values at high power output). Lots of guessing in that video.

Wow…great idea! May I ask how did you make that analysis?

I dump all my ride data into a database (basically grab the data from Strava and transfer it to a database).

Run some Python code on it. My job has a lot of data science aspects, doing things like this come easy for me. This is not overly complex to code.

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Is anyone regularly using DFA Alpha 1 to ride under the aerobic threshold?

I got a Polar H10 and HRV Data Logger. It seems to work pretty well. My aerobic threshold seems to be bang on with what I determined years ago with Seiler’s 60-70% of HRmax estimate. For me that range is 113-132bpm.

On my first DFA Alpha test, I was staying above the .75 threshold right at 130bpm. If my HR blipped up a couple of beats I’d dip under the threshold.

On my second test, about 125bpm was right. 128bpm pushed me under .75.

I was also extra tired, and noticed that 45 minutes into the ride I had to lower the intensity quite a bit to around 123bpm to stay above .75.

So what is the conclusion with DFA Alpha 1?

Just keep riding at 125bpm or under for low intensity rides?

Do intervals at 125bpm to track power at that HR? A gauge of aerobic fitness?