Dr. San Millan's Z2 Rides

Podcasts Fast Talk
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some random thoughts:

  1. fatOx requires O2 and happens in the mitochondria
  2. lactate Ox is the same (e.g. lactate produced in slow twitch or lactate shuttling of lactate produced in fast twitch)
  3. lactate can also be converted to glucose by the liver

1 & 2 both require mitochondria capacity.

  • I am assuming 1 & 2 look the same when we measure RER (respiratory exchange ratio). I.e. FatMax is really mitochondria max – both go through the krebs cycle.
  • I don’t recall Milan or anyone else talking about measuring 3 but this is part of lactate clearance

If lactate going through the krebs cycle looks like FatOx from an RER standpoint (I have been assuming RER is how Milan is measuring FatOx) then FatOx going down means the mitochondria is clearing less lactate at higher intensities and we are relying more on 3?

I seem to recall that the heart prefers lactate as a fuel but I have no idea how much this contributes to lactate clearance.

I never studied bio in college so I really I could have everything wrong. Please let me know what you think.

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My rule-of-thumb for LSD (zone 2) rides is ride easy, really easy. If I can stay chatty, I’m in the zone.
A power meter isn’t really a useful tool here, but a HR monitor is.

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Thanks for sharing your opinion. Have you done anything to assess how that works out in terms of results (mitochondrial density, power at AT1, etc.) vs doing another block of training at a slightly higher intensity?

Asking because in recent interviews, many of which can be found on YouTube, Dr. San Millan seems to indicate that his view of “Zone 2” may be “not quite as easy” as just riding around. He says things such as “you can hold a conversation, but not as easily and fluidly as when riding truly slowly” and “these rides are still challenging”. He also seemed to equate the intensity he has in mind as being pretty close to “fat max”, which would be higher than most of us would have in mind.

I have not found any specific data that would help pin down what one is supposed to do to reap maximum benefit of this kind of training, certainly not when the wish is to maximize use of time.

(I suspect that with basically limitless time available, as long as the easy rights are long enough, it may not matter much what the intensity is, as long as it’s low enough. But I suspect that when one only has 1-2 hours to invest per session, then it might become important to make sure we don’t go too slow, while not going too hard either.)

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I haven’t done any lab tests at all in this regard. I’m also trying to develop other aspects of endurance not only mitochondrial biogenesis, power etc. in my athletes such as fatigue resistance and durability, lipid utilization, bio-mechanical and psychological skills among others.

I seem to recall that somewhere Dr. San Millan stated he doesn’t prescribe those zone 2 workouts longer than 90 minute to 2 hours, although I may be mistaken of course. The stress of a 2 hour ride at 85% TP (tempo) is about the same as 4 hours at 55% so that makes sense if he is prescribing high Z2 workouts.

There is a 2018 meta-analysis by David J Bishop et al on “High-Intensity Exercise and Mitochondrial Biogenesis” that concludes, among others, “there are conflicting findings in the literature, and a consensus has not been reached regarding the efficacy of high-intensity exercise to promote mitochondrial biogenesis in humans”. Even within this paper, there seems to be some different terminology to what we I use. They use Wmax whereas I think they may mean Max Aerobic Power from what I see in graphical illustrations.

They defined moderate intensity as <75% Wmax, high intensity as >75% and sprint intensity as >100%. These correspond to moderate to high Z2 (tempo), Z3-4 and Z5+, similar to Seiler zones, 1, 2 and 3.

One conclusion expressed is “exercise-induced changes in mitochondrial biogenesis in response to high-intensity exercise may therefore be more strongly associated with exercise intensity expressed relative to the LT than relative to Wpeak or Wmax.” Same thought at Drs San Millan, Seiler and many others.

Back to the question of where to focus intensity, I believe in an smorgasbord approach. A variety of duration and intensity in Z1 and 2 will deliver a variety of adaptations that are not conflicting and beneficial to endurance development. This also allows for the athlete to have control of the workouts they choose without causing repetitive boredom or compromising the goal.

I think low-intensity workouts should be kept simple, easy to monitor (during the workout and in the analysis) and let the athlete have variety and control.

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“If you have any more questions about Moxy don’t hesitate to ask.”

I will take the liberty, Steve. I don’t know much about Moxy, looked it up on the net, there seems to be some research that is equivocal on it, but I may have misread or haven’t read the fuller body of evidence.

Can you comment on the science behind it as to accuracy and reproducibility? And why consider using it?

From your posts over time, I see that you and your clients use it. And that you use lactate testing.

I am endurance rider primarily interested in LT 1 right shift. My big interest is knowing when during a slow steady long ride is the best time to stop.

On a particular day, at the usual low intensity, when is my body ready to create adaption without further stress? at 2.5 hours, 3.5 hours, 5?

I can use cardiac drift while on the bike, not so easy to measure while riding, and Seiler said “But cardiac drift is not the best measure, can be off.”

How does it compare to home-based, or lab-based lactate testing, generally speaking? Someone posted that they noticed around 50% of home lactate testing done by their clients had numbers off the mark.

It would be great, especially for us time-crunched amateur warriors, if there was a reliable metric that during an endurance ride said: “For today, you’ve done enough, you don’t need another hour, go home and feed the cats.”

Or “Screw the cats, keep riding.” :slight_smile:

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Hello @micomico I will let @SpareCycles tackle the accuracy component, in his profession he will be able to give you a much better answer than I.

Regarding what you are looking for to aid your training, there isn’t a better device.

You can basically find your LT1 (aerobic thrreshold) every, single ride.

I actually prescribe my atheltes endurance training in a wattage, heart rate range, but the main piece is to make sure that the smo2 is constantly rising.

Once you are familiar with warming up properly (which the device can also help you with), you can then find your peak wattage to ride at each day for the rides you are describing.

You can also do testing on yourself to track your progress in a more stable, indoor setting.

However, the reason I use it so much is because every single ride can be at the right intensity…sometimes harder than you normally go…and other days noodling home to feed the cats.

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Thanks, based on what you said it seems like a great tool. I assume @SpareCycles will get the email.

This could be a perfect case in point for it. This morning I rode for 4 hours at a stable average of 69% of Max HR. Sounds good, right?

My legs didn’t feel good. Although I rarely went above 70%, I started decoupling almost immediately, 5% in the first 30 minutes, and lost 30 watts at the same low HR in the last hour. I should have stayed home and played with the cats. Or dropped down 15 watts or more to start with.

I assume that is where something like the Moxy could have helped.

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I think you knew how you felt during that session without the moxy. However, it will really help give you the confidence when to go feed the cats.

There are also a number of different tests and during session check-ins that can really help.

All the best!

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Yeah exactly this :point_up:

Sounds like you knew what the ‘better’ decision was that day. At least in retrospect. Next time you’ll be able to recognise those same sensations earlier and act accordingly.

“Sometimes adding more data adds precision,
Sometimes adding data adds flexibility,
Sometimes adding data adds confidence”

This is probably the third case. IMO Moxy / NIRS is not gonna add much further precision to to what your body can already tell you about when your adaptation / fatigue ratio is optimised. But as per @steveneal’s great advice it can give you the confidence or ‘permission’ to listen to your body.

As for test-retest reliability / agreement, we’re writing a manuscript on that now. Others have looked at Moxy before (e.g. Crum et al 2017 below), although have not systematically quantified test-retest agreement. As in, by how much (units %) is SmO2 expected to differ between any two sessions?

Sneak peak of our results are that it’s around ± 5-7% depending on exercise intensity. Which is what Moxy themselves have said for a long time (“within ~10%”). We’re also comparing that in context of other typical measures: VO2, BLa, HR, etc. SmO2 stacks pretty well against these other established measures.

Accuracy is another question… ‘accurate to what?’ :man_shrugging: :grinning_face_with_smiling_eyes:

Agreement between measures of the Moderate :arrow_right: Heavy transition (LT1, VT1, oxygenation-BP, etc.) is complex and I don’t think has been done well with NIRS. I’ve talked about and shown the agreement among aerobic threshold in our dataset on twitter a few times, incl. here
https://twitter.com/jem_arnold/status/1577278071836581889

Caen et al. have I think an excellent discussion on the meaningfulness of comparing threshold measures in context of the Heavy :arrow_right: Severe transition (LT2, VT2, CP, FTP, MLSS, etc.) See below (freely available). Very worth a read of just the intro & discussion for the philosophical takeaways, IMO

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Thank you! The reliability/agreement according to other research seems to be higher at lower intensities, which you noted: Sneak peak of our results are that it’s around ± 5-7% depending on exercise intensity.

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That’s right. Interestingly, most physiological measures increase along with intensity, while SmO2 decreases with intensity. Meaning that while the absolute error increases for VO2, BLa, etc. as well as for SmO2, the coefficient of variation (CV, %) for the former decrease (i.e. the mean value increases more than the absolute error) While the CV for SmO2 increases (larger error over smaller mean value).

So the lower CV for SmO2 at higher intensities is kind of an unfair comparison to other physiol. measures.

Would it be useful to discuss the ‘applied meaningfulness’ of e.g. ±5 %SmO2 vs ±500 ml/min VO2, ±1 mmol/L BLa, etc. (I’m making those numbers up) for better interpretation?

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Thanks for asking, for me I need to keep it pretty simple; so at endurance level rides Sm02 is more accurate than tempo/threshold/intervals?

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I would say no…not once you understand smo2 trends.

It can be useful at all intensities, at differently levels.

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