periodic intensity vs fatox from someone who knows a thing or two about physiology
https://twitter.com/coggan_andrew/status/1497930964063899653
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Periodic, sure. What about chronic bouts of intensity? (Probably doesnāt apply to most on this thread but almost certainly applies to many riders)
What are chronic bouts of intensity during a long endurance ride?
Coggan refers to his study where they alternated 15min endurance with 15min at FTP for ~3h. And he saw that there is no reduction of fat ox after the FTP bouts. the opposite acutally since endogenous carbs run out.
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I think I heard ISM arguing the other side. But he didnāt specify above or at FTP. So it could be the case that itās only work above FTP that inhibits the adaptations of endurance work, and they are both right. It would be nice to get clarification from ISM.
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Now weāre really running the risk of mixing up different contexts.
Day over day. 3 x week, week after week (or something like that). We see fat ox rates climb back up after the 15min bouts of intensity, but we also have less time at which rider was using fat (preferentially) as a fuel source. Just to make sure Iām understanding correctly, he is not saying fax ox rate was same during the 15min at FTP part. It drops, then comes back up. So overall, we have less fat ox ātotal timeā versus a ~3hr ride with no intensity.
Iām asking (because I donāt know, not because Iām starting a silly internet forum debate): if a rider spends considerably less ātime in zoneā (at or near Fax Ox), does it matter? To put it another way, is the long slow ride of 4hrs really different than a 4hr group ride? (in terms of Fat Ox).
We do see some evidence that being precise with low-intensity exercise prescription may not be that important:
So overall, maybe it is solely duration-dependent? Just get the work done (regardless of intensity), and fat ox takes care of itself 
If nothing else, it addresses the āhey, coach, did I ruin my long ride by going hard up that hillā question. Likely, you did not.
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I donāt have a background in exercise physiology. My understanding is that adaptations are driven by the number of muscle contractions, and very little intensity is required. So duration.
Similar for some cardio adaptations. Iāve even heard either speculation or evidence that the heart may develop āmore elastic reboundā by training at lower HRs I dunno, didnāt bother chasing it down on PubMed.
So then the training question comes down to other factors, like managing fatigue from other training/life, and other aspects like for me personally pushing at 70-75% on 8-12 hours/week target makes it either mentally or physically ābetterā than 55-65%. Better in terms of perceived and measured performance. I donāt know or care if its mental or physical (or both), its just better for me.
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First of all I donāt think it is possible to say one session is better than another. Endurance is built in blocks, considering the the average half live of adaptions 3-4weeks blocks (source: again Coggan).
I donāt know if one has to ride at fatmax to build fatox (especially at higher intensities). All I know:
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Bu says Blu was carb thirsty. He did plenty of volume <LT1 and this shifted fatox at race pace to the right
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training volume (no necessarily duration) is one of the few parameters where we really see a strong correlation with mitochondrial content. And the more mitochondria, the more fatox. However, we also see an increase in intramuscular fat with high volume. The fat glycogen so to say. Close to the mitochondria. Adds to higher fat ox, the substrate is there.
Type I and IIa fibres in two different muscles:
I donāt know if it is volume at fatmax or just volume. However, I donāt really know if this is relevant since the āhigher fatox zoneā simply coincides with an intensity level where one can accumulate a lot of volume without overdoing it. Too much can impair recovery. Impaired recovery equals less adaptions. At some point there is no subsitute for volume. As WW has said, the number of muscle contractions are crucial as well. These trigger vascular adaptions. Supply lines for your mitochondria.
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And how do we look at signaling? Yesterday I just gave my body 6.5 hour signal that built on progressively longer signals the weeks preceding.
In the past one of those ālong for meā signals a month appeared to help build fitness over 4+ months.
Is it possible to see signaling any other way, without lab visits?
Right, you donāt need a lot of intensity to drive adaptation signaling. You need duration.
having built many mathematical models of molecular signal cascades in my previous professional life I can assure everyone: just because there is a signal does not mean there occurs an adaption. The body produces signals all the time without actually really picking them up. Often itās an inactive receptor. I know PGC-a and so on. Yes, folks measuring just mRNA and then concluding the treatment x causes this adaption caused by PGC-a. Ufff ā¦
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I used to want to understand whatās happening inside the body, however after reading a bunch of pubmed stuff and conversations like this thread, it just further drives me back to what experienced coaches and coaching companies recommend. And from a self-coaching perspective, focus on small 3-4 week āexperimentsā (or several blocks worth) and get good at a) interpreting your day-to-day feelings, and b) reviewing the two most basic measurables (power and HR) for changes.
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Thanks for the thoughts, guys.
Do as much as you can, as hard as you can, all the time. - My High School XC Coach
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Sure, but we are not talking about any signalā¦but muscular activityā¦to quote Viru, who wrote a nice book on this precise topic:
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This is my take on it. Also it allows the athlete to do enough intensity for his goals whilst still maximising his volume and getting most bang for his buck. On Twitter I seem to recall ISM saying he didnāt know how heās become known as a solely Z2 guy āMy riders do a LOT of intensityā he said.
Different sources say that he prescribed almost only Z2 in the beginning. Apparently he moved away from this over the years, seeing the WT pros need a turbo diesel, not just a diesel.
What Iāve found interesting to note, McNās training this winter compared to last winter. So much more intensity this winter. And in spring these epic tempo or SST sessions. Different to last year. Adding to this his Thomas De Ghent style wins this early season.
Overall one can note how UAE has notched up its game across the board. I donāt know if this is now confirmation bias from my side but it appears āgeneral fitness/enduranceā is stronger. Just the way how they ride and how individual riders have developed so far. Rest of the season will be interesting.
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And in general, for ISM, the intensity āācapāā is suprathreshold (so at or just above lt2)? Or is that only because he mainly trains guys that need that type of intensity for their events?
Mmmm ā¦
I heard on one of the numerous podcasts he was on that the intensity is appropriate to the specific event. So if thereās an uphill finish the intensity would be s lot higher than if you were training someone for a lone breakaway win. Thing Pog & McNulty possibly
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After being more interested in physiology for the last few years and listened to/read a lot of commentary on a variety of topics, Iāve come to the same conclusion. In fact, this has led me to be fairly suspicious of big claims being made based on some very specific signal/mechanism at a very low level. Whether we are talking about the effect of an exercise intervention, or some supplement or medication, focusing on a highly specific and very small mechanism as āproofā that it has some much larger/broader impact is now a big red flag for me. Even if what is said about that mechanism is correct, and it really is observable, does not mean that it has the broad effect that is ascribed to it, as generally there are many other factors at play that are also important in producing the desire macro effect.
Discussing and analyzing signalling and mechanisms is absolutely appropriate in the right contexts, however I find that these types of things are very often promoted inappropriately in the wrong contexts (both inadvertently and deliberately I think.)
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