Zone 2 training with Iñigo San Millán, part 2

It depends how many days in a row you do it and whether or not it’s making you tired by the end of that many days.

With torque training it’s advised not to do too much of it. I do it once a week, often before a Z2 day or a recovery day. My torque session last week was yesterday at an average of 90% of my FTP. I count that as a hard day. Today is a recovery day.

I would most likely die…

Jokes aside, would be interesting to hear more about your physiology: LT1, LT2, weight, %HR at different efforts etc.

My LT1 (which is what ISM targets) is 255w, my LT2 is 315w.
LT1 HR: 170-175
LT2 HR: 190-195
Max HR: 207
Usual HR for endurance riding 145-165 (usually average around 190w)

I do rides with LT1 intervals, e.g. 2x30min at LT1 etc.

It sounds a bit off though that your “near tempo” Z2 is 70% of your HRMax? At that HR I am riding in low low Z2…

I haven’t done any actual lactate testing, so I can only presume some of these things:

weight: 60kg
presumed LT1 230w
LT2 (FTP?) 290w before testing after this block (probably closer to 300w once adaptations happen). I was up to 305 last october, but caught covid which hampered my training for over a month and dropped to around 275.
Presumed LT1 HR: 130-135
LT2 (Threshold) HR: 170-173
Max HR: 190
Resting HR: 34-36
Usual HR for endurance riding around 190w (65% ftp) is 110-115. Barely any hearrtate drift even on 5+ hours rides. If drift happens, it’s usually negative (HR goes lower for the same power the longer the duration).

The (presumed) LT1 intervals I’m doing now are 10min warmup, 2x80min at 80% ftp seperated by 5 min at 60% ftp and a 5 min cooldown. I feel like I could do without the 5min break, but I usually need to stop once anyway to go pee, so might just do that in the middle.
These intervals are right between the top end of Z2 and the low end of tempo for me. So, yes, my near tempo HR is 70% of HR max. As I said, according to a muscle biopsy I’m almost all slow twitch fibre and don’t have any sprint. I can barely hit 800w and my all-time 5s power is 730w lol.


I can add another n=1.

LT2 - 330w, LT1 - 290w (recent lactate testing w/ 6 min steps from finger), max HR ~190. Did hour @ 270w (81% of LT2), averaged 138bpm (73% of HRmax).

[Updated] majority of volume (~10h/week) done at 180w (105-115 bpm depending how much I ate before), RHR ~48, weight 86kg. 43/57 slow/fast twitch.

A bit of caveat, I am coming from running and feel that my legs (peripheral adaptation) are still slightly underdeveloped compared to cardiovascular system.

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I have been looking at this for a while now and just wanted some feedback from folks. I have been doing SSLV and just finished low volume 1 with 2 extra endurance rides added weekly. I am starting base 2 next week and I am currently thinking about switching the sweet spot day for an ISM zone 2 and adding 2 additional ISM zone two days for a total of 5 days training with 3 ISM zone 2 and then a vo2 day and a threshold day. I would set up a custom workout for the ISM days at somewhere between 65% and 75% FTP (tbd) and adjust the intensity to keep my heartrate in ISM zone 2. This way TR takes care of my intensity progressions and I manage my zone 2 progressions. Does this make sense or is there a better way to do this? My current goals are recovering my fitness from covid, and base work for the Cyclocross season.

I would say that its a lot of intensity…

If I were you I would set it up as following:
Day 1 - Hard intervals (V02 Max or Threshold)
Day 2 - IF 0.6 Z2
Day 3 - IF 0.6 Z2
Day 4 - Mid intervals (2x20 ISM intervals, build up slowly to 2x45min)
Day 5 - IF 0.6 Z2 OR another Mid Intervals session depending on fatigue, if feeling any fatigue, keep it IF 0.6 Z2

Then either have 2 consecutive rest days before going again, or do one rest day after day 3 and day 5.

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How are you assessing your “ISM zone 2”? How does the above % differ to your current z2/ endurance work? Assuming the outlined 65-75% FTP is a step up from your normal endurance %, then I would think that your plan is a lot of intensity which may or may not work for you.


I am a bit confused on this as I did not think they counted as intensity days. I will be researching more. It is a big big thread with lots of head scratching for me.

Thank you for this recommendation! I actually have a lot if difficulty with .6 IF in that I don’t get my heartrate high enough to feel any workout effect. These feel like recovery rides and my heartrate stays between 90-105bpm. the top of my zone 2 is 130-135 based on HRM and talk test. I think I would do these at .65-.67 but I get the point.

No lactate measuring for me. I started at .7 and did consecutive days maintaining my heartrate just below my zone 2 cap over a single 1 hour interval. Doing this I rarely move the intensity more than 5% Maybe this is totally wrong?

Thanks again for the thoughts. I am interested in this because I want to get a good training effect with 5 days per week and 60-90 minutes is my realistic available training time per day.

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Just to give some clarity on my zones, as a comparison. My LT1 is 255w, my HR during LT1 is around 170-175bpm.

When I ride normal Z2, I ride around 180w, and HR is then around 150bpm, and yes its very easy, but thats the whole point :slight_smile: I don’t even breathe with my mouth open most of the time haha.


So, below threshold we have:

  • Easy z2
  • Normal z2
  • ISM z2
  • Low Tempo
  • Tempo
  • Sweet Spot.

No wonder the traffic in these threads. Only 1 of those zones can be objectively validated and even so, very dependent on protocol.

Hope someone makes a lot of money out of this situation.


ISM zone 2 and low tempo are the same.


do this enough while paying attention and you might figure it out in the field for yourself.

Post ride I also look at Garmin performance condition, it uses machine learning on HRV, HR, and power.

A good day, two weeks ago:

that +2 is generally what I see during a slow rise in fitness. And power chart:

Versus this week after reduced training load last week (traveling):

that -2 is generally what I see during periods of reduced training load. And power chart:

next morning (yesterday) my RHR was up 5bpm. Sleep was just so so. Likely a little bit of stress from that endurance ride, from getting back in the groove after traveling last week.

And then last night another 2 hour workout with intervals, performance condition at 0, felt fine during and after, and woke up this morning with normal RHR.

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Yeap, that is about right.

I’d put it this way for well trained…

  • Easy z2
  • Normal / mid z2
  • High Z2 / ISM z2 / Low Tempo
  • Tempo
  • Sweet Spot.

And this way for off the couch…

  • Easy Z2 / ISM Z2
  • ISM Z2 /Mid z2
  • High Z2
  • Low Tempo
  • Tempo
  • Sweet Spot.

A couple podcasts on this idea:

Exactly. Worth a listen.

and this one:

(around 14:45 he briefly talks about “not ruining anything” by going into zone3)

Both basically say the same thing, don’t get too caught up in the current hype of “zone 2” training.


Last week I did another one of my simple experiments to find the boundary between stable and unstable physiology. Some promote Critical Power tests, I just find it on the ride by riding around “FTP” without having to ride for some indeterminate amount of time.

Here is what my HR looks like when riding just above stable physiology:

just to make sure I push the power a little higher:

Yup, the separation between stable and unstable physiology is somewhere around 280-290W.

From Skiba’s Scientific Training for Endurance Athletes:

I’ve been doing this since 2017, its really not that hard to find with simple field testing.


I kind of like his model. The whole idea of FTP and TTE doesn’t seem robust enough for me.


One more podcast for the ISM fans:


At this point I just wait for ISM to appear on Joe Rogan :rofl:

ISM: By riding in Z2 you increase mitochondrial function.
Rogan: That’s crazy man. Have you tried DMT?


Just uploaded today. Every time I listen to him or Seiler I want to change my training. Then by the time I work through all the realities, I end up back at low volume with 3 added endurance rides :man_shrugging: