Inigo San Milan

I just found this! What do you think?

" I am not sure how valuable this information is to this thread, but I was actually tested in Inigo San Millan’s lab here in Denver at the Anschutz performance center back in 2016. You simply paid some money, did a few tests, and were prescribed a training schedule. I was a 35-year-old runner at the time and had never tested any of these metrics despite having a solid running career. I was thinking about training for a fast half marathon. I started cycling in 2019 but had no concept of cycling when I went to his lab. I only did the VO2 max test, but along the way, my zones were calculated based on fat vs carbs. I don’t remember much about the general conversation other than being told not to barf in the mask, but I still have my lab report and prescribed training. I was given 3 prescribed zones: Zone 1-2, Zone 3, & Zone 4+ My max HR was 193. My zone 1-2 was 153-162, Zone 3 168-171, and zone 4+ 180+. Again, this is running not cycling.

A few interesting notes from each zone:

Zone 1-2: Recovery and Base endurance. This is from rest up to your aerobic threshold. This is where your body is most efficient at metabolizing fat for energy.

  • Zone 1-2 days should be a gradual increase up to the top workload and heart rate in the zone
  • This is your recovery or easy zone

Zone 3: Threshold and Tempo. This is just before your lactate or anaerobic threshold and is typical (sic) the race pace for endurance events. Here is where you build tolerance to exercise.

  • Always start with your specific warm-up it’s designed to enhance fat utilization.
  • Stay at AT/Zone 2 workload for the entire interval.
  • If the Zone workload is giving HRs above the top of zone 2 or below the bottom, report back to your coach.

Zone 4-5 Peak or Anaerobic training zone, it is not an all-out sprint. This is where you improve your peak VO2 and burn the highest calories

  • Always start with your specific warm-up it’s designed to enhance fat utilization.
  • Zone 5+ or Peak VO2 workouts must stay at Zone 5+ workload and HRs for intervals should be zone 3 and above.

It also suggests strength training days where you complete the specific warm-up before strength routine and do strength training 2x per week. No actual lifting or strength program was ever discussed that I remember.

The Warm-Up Page. Lots of notes here. My specific warm-up was starting at an HR of 143 with 2-minute intervals increasing it to 171 over 10 minutes (143, 152, 159, 163, 171). I was given treadmill speeds for each 2 minutes. Notes on the page:

  • Warm-up should be performed on all Zone 3 and 4-5 training days. After your warm-up, take a 3-5 min easy recovery. On your Zone 1 days use the first 8-10 minutes to slowly warm-up.
  • If your heart rate after warming up is + or - 4 PBM, please notify your coach. (This was underlined!)
  • If at any time you feel like your workouts are too easy do not increase speeds unless you have spoken with your coach. We are teaching your body to favor fat and spare glycogen at the highest speed possible, speeding up to soon will decrease your results.

I was given 4 weeks of training. All included 3 days of base building with one day as long aerobic. Plus a VO2 max day and a Threshold day. In order of each week the workouts were:

VO2 Max:

  • 10 sets of 2 minutes (180+)
  • 11 sets of 2 minutes (180+)
  • 7 sets of 3 minutes (180+)
  • 10 sets of 2 minutes (180+)


  • 6 sets of 5 minutes, 1:15 rest (168-171)
  • 7 sets of 5 minutes, 1:15 rest (168-171)
  • 3 sets of 6 minutes, 4 sets of 5 minutes, 1:15 rest (168-171)
  • 2 sets of 7 minutes, 3 sets of 6 minutes, 1:15 rest (168-171)

Zone 1-2:

  • Simply prescribed time. 2 days at 50 minutes (Running) and one long day at 70 minutes. All HR between 153-162)

Okay, long post, but as it pertains to this thread, this is straight from ISM himself. Although, it’s 5 years old and things could have changed.

I did a DFA a1 ramp test with a Polar H10 and AI endurance and sure enough, my AET came out at 157 BPM on the bike. My anaerobic threshold according to AI endurance was 174 BPM. I have a ramp test FTP of 272w as of December (old I know). My endurance celiing cluster on AI endurance shows 228w and 157 BPM which right now for 60-90 minutes I’ll be right around that probably drifting to the low 160s. I did a ride with a 10 min warm up and a set 215w for an hour and my HR drifted from about 150 BPM to 156 BPM over that time.

I am not an expert. Just trying to provide some hopefully interesting data and information. I think the big take away for me is that this upper zone 2 is closer to what most standard metrics consider tempo. I am also curious that the HR +/- 4 BPM is a concern. Most of my reading suggest HR zones can be 10-15 BPM and it’s no big deal but according to this a small difference is meaningful.

In general, my anecdotal experience is that this all lines up. I can hold 173 BPM for about an hour when throwing down a big climb. I have done 2+ hour rides averaging 150 BPM while it’s an effort, not soul-crushing, and somewhere around 180+ I start to see god (turning 40 much more so)."


ISM: “An endurance athlete should never stop training in zone 2. The ideal training plan should include 3-4 days a week of zone 2 training in the first 2-3 months of pre-season training, followed by 2-3 days a week as the season gets closer and 2 days of maintenance once the season is in full blown”.


Thanks for sharing. In fact, depending on who you talk to, the ISM zone 2 (or even the Seiler zone 2) is harder than we think. I always try to be at the upper end of the zone, so I’m kinda sure it’s okay. Based on no research really although I do lactate tests. Peter Attia’s explanation is helpful: “you can talk in sentences, but it’s definitely harder than sitting on a coach. You gasp for air after 2-3 sentences but it’s never straining.”

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@Xavier_Hipolito_Marg Thanks for sharing. My first take is that your zones 1-2 (Zone 1 on a 3 zone model) were incredibly high. Most of us will be much lower than that. There’s also a good chance that they’ve come down for you over the past six years.

@Steven_Vanlancker, the zone 2 upper end is a cap not a target. :wink:

FYI, from Netter’s Sports Medicine, ch. 18 Aerobic Training by John C. Hill, Inigo san-Millán

yes…zones in my head are always a range, no target. When I hear people talking about 2 watt gain, I’m gone…


I agree, these numbers look like an indication of very developed athlete, with AeT close to AnT and all the zones “compressed” to the top of the range. And then it totally makes sense that with narrowing of the zones you need so precise 8 bpm interval.

Just to provide context I think its fair to reference the source of the text to provide context etc. The OP has extracted text from this post (Iñigo San Millán training model - #1026 by BTSeven7 - Training - TrainerRoad) on the TrainerRoad forum which is part of the a long standing thread discussing the ISM training model (Iñigo San Millán training model - Training - TrainerRoad)


Mahalo @Olly_Thomas! This puts it in much better context.

A thing I normally do when training that zone is talking sentences to my self to see if I’m in the zone :joy:
“I’m really, really, really, good” and in that “good” I need to breath in again or I die


Sorry, you’re right, let me put it in!

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Inigo is pretty clear saying that Z2 is the range where the FatMáx occurs. But where starts Z4 and Z5? The Long intervals he prescribes, like zone 4, starts when Fat oxidation is 0?

"You can make relatively quick changes in your glycolytic efficiency. You can take an untrained person with a vo2 max of 20 and you could take them to 30 in a period of months with the right amount of training. A 50% improvement in a few months. It’s very difficult to see a 50% improvement in mitochondrial function in a few months. It speaks to why this level of training should be thought of in the same way that you think of accumulating wealth: which is it’s day-in and day-out small compounded gains over years and years. "- Peter Attia


I am new here, but have spend quite some time reading lots of fantastic stuff, on this great forum. Thank you so much to all of you for the insightfull and inspiring contributions. I try now to maybe give something back to those of you, who still like to use, and discuss/learn heart rate (zones). Inigo San Millan etc…, maybe this could be of a little value.

Thank you very much for the paper(table 18.2) :+1:.

Im struggling a bit with the Heart rate zone 2 and 4 also though. I know it is just an example and not generic/applicable in general. But, I dont have access to prober testing, and I am an old school heart rate guy so…

The power zones, in the table, are almost classic (Coggan/Inscyd)

Zones in %FTP (264watts)
z1, (AR) < 56,8
z2: (E) 57 - 75,8
z3: (T) 76 - 92.8
z4: (LT) 93 - 1.08
z5/6 (V/An) 1.08+

I find the heart rate zones (HR)from table 18.2, a little strange though.

The matching heart rate zones for 2,3 and 4 based on LTHR:145, are in this case

z2: 82-88% (119-128) (not 103-125)
z3 89-93% and (129-135)
z4 94-100 % (136-145) accordingly

If he/she wants to train the turbo (glycolytic) it is best done around 97%LTHR or higher!
In this case, when talking heart rate, zone 4 starts 9 heart beats under LTHR (wich is close to Neal Henderson, Sufferfest/Systm) and his definition of sub-LT

In some cases using google I have seen Inigos Zones 2-4 being like this:
zone / %Lthr/ (beats from lthr)
z2: 85 - 91 (Minus 15 to minus 25 beats of Lthr) , target 88%lthr
z3: 91.5 - 96 (minus 6 to minus 14)
z4: 97-100 (lthr minus 5 to lthr)
**z5+: 101+ (lthr+1 and above)

In conclusion from this table, and those three tables I have found:

If you are a trained cyclist using heart rate as a guidance. you could go on like this.
An athlete should never stop training in zone 2, with a target of 85 - 88 % LTHR, or 75 %FTP and a range of 85-92%of lthr. This falls in line with “Olympiatoppen”, Norway, and British cycling) who labels everything below 82 % off HRmax low intensity. Maybe it also falls in line with Seilers new 2-zone-model around Lt1. We will wait and see.

I am sorry for the length, and poor editing. Im more confused than when I started (All I know is that I know nothing, and soforth)

Even this for pro is too high for what they do!
You are more than welcome in this post and thanks for sharing your thoughts, it’s always a pleasure to discuss training!

Thanks Xavier. And yes it seems high, but Inigo zone 2 also seems a bit higher than ex. coggan zone 2. More like low/mid tempo a la Steve Neal or something. I have tried it out this year and it works in the winter, but when I have to train the hard sessions more frequently (x2 week) i always fall back to easier rides than Inigo prescripts. At least I think.

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The challenge for the pro is that their LT1 and LT2 are only about 8 bpm apart. Hence why they have to be careful going over LT1 as it may take them over LT2 very easily. With most amateurs having a gap of 20-30 bpm between LT1 and LT2 they can afford to be a little over LT1 without worrying about going over their LT2. Most amateurs don’t work on raising their LT1 , hence the large gap.

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This was discussed in Aerobic training and testing with Scott Johnston | EP#326


If you watch McNulty trainings on Strava you see that most of the zone 2 rides are probably between 230-300 watts with HR beeing low, like 130 bpm. I saw in a training 184 bpm, but he probably can reach 200. As you see, zone 2 is quite high in power but the HR still low. Maybe we’re doing wrong in pushing the HR up, don’t know

I don’t think so Phil. It’s kinda individual. For some is just 10 bpm, for others 20…
I know a very good world tour with 155 VT1 and 175 VT2