Your “resting” levels are already elevated, which is why you see an initial drop during exercise. Either your athletes are stressed psychologically, and/or they simply haven’t been resting long enough to obtain true baseline values.
“Tougher” individuals (literally…google “toughness theory”) demonstrate a greater catecholamine response to stress, which is probably why you see it more in better-trainef cyclists.
Forgive my exercise science naivety here, but in layman’s terms, is this not quite similar to a polarized training approach?
A few days of Endurance focused sessions to facilitate mitochondrial biogenesis, mixed in with a few sessions at threshold and/or VO2 to assist with lactate clearance and to increase the glycolic enzyme number.
“Zone 2 (Z2) has shown to be the training zone eliciting the best results to improve lactate clearance capacity.”
My overall, limited n=1, understanding:
I’m guessing this is to increase mitochondrial biogenesis and thus more MCT-1 (lactate uptake - slow twitch) to accept the Lactic Acid from the MCT-4 (fast twitch) in order to excrete the H+ ions (through respiration) and recycle the Lactate as ATP. This then ensures that acidosis doesn’t occur (increase in H+ lowering the blood Ph) in the body and performance is maintained.
Therefore, constantly training at threshold and neglecting Z2 doesn’t really assist Lactate efficiency because you’re not generating the necessary MCT-1 in the slow twitch fibres. The misconception here is, “I must constantly train at Threshold to improve my Lactate Threshold”. In actual fact, this is only half of the equation. You also need Z2 rides to support mitochondrial biogenesis to assist with the whole Lactate processing process. Also, constantly training at Threshold also leads to burnout.
Mind blown. Light bulb moment for me right there. Just even regurgitating that in my own head makes me feel like I’ve just earned my Masters in Exercise Physiology 
That’s what I see too, same limitation in exercise science.
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.
pre season yes but the rest of the season does not look polarized to me
apart from that, with Seiler I always get the impression that LIT is more the filler/recovery for the two hard sessions. Here the focus is more on the right edge of the LIT spektrum (not slow). However, I don’t know what polarized recommends exactly, Seiler talks a lot but says little. No secret, I’m not a big fan of him. Therefore, my view on polarized is very biased.
All I can say is that riding base at this pace (outer edge) is a much more entertaining experience, now I just have to get lactate analyzer. This has been on my “I-want-list” for quite a while.
Where does sweet spot fit into all of this please?
Looking forward to where this thread goes 
I think this is also an importnat post from the Pro Cyclist thread:
@Matthew_Taylor this sums it up pretty well.
Sweet Spot is the border of Z3 and Z4 around anchor point LT2 - roughly 90% FTP.
My N=1 understanding is below. Very happy for expert opinion on the below musings.
Sweet Spot would fit at the lower end - perhaps even the starting point - of the glycolytic training he is referring to.
The very nature of Sweet Spot training is bringing yourself to the point where Lactate uptake and clearance reaches somewhat of a neutrality state. Anything above that, even slightly, would force adaptive changes in the mitochondria and MCT-4 efficiency to shuttle Lactic Acid to the MCT-1 in the slow twitch fibres as the mitochondria ‘struggle’ with the added load above the current homeostatic limitations.
That said, time in Steady State at a given percentage beyond TTE would seemingly also force the same adaptations as there seems to be a time based inflection point during Steady State where the same adaptations occur as the mitochondria become under stress as the oxidative stress increases.
My wondering is whether or not this would lead to the same adaptations as mentioned above. Very happy for some expert opinion on this. Lots of knowledgeable TR users who have done years of study on the above and I hope to read their commentary.
Thanks for the detailed answer.
Does that mean that SS potentially ticks both boxes of Z2 and Threshold when training with limited time <10hrs.
I wouldn’t think so, but:
From those graphs, it looks like his zone 2 is between the top of the fatox curve and the crossover point. Then, why does he define it in lactate measurements? Is it just because lactate is easier to measure?
I’m struggeling with this upper edge 75% VO2max. Still don’t believe fully that it is actually his zone 2. For him it does not matter because he would not prescribe training based on vo2max.
I wouldn’t have thought so @Matthew_Taylor. My understanding is that Sweet Spot is that area of upper Tempo and lower Threshold. The ‘somewhere between’ amalgamation of both zones depending upon your % FTP and Lactate clearing abilities at that % FTP etc.
Zone 2 is labelled in that graph as below 80% HRPeak however, I have heard of other research and platforms pulling that back to 75% to represent LT1 (aerobic threshold).
This podcast is worth a listen. I always love listening to Jonathan Vaughters talk about sport physiology and different training techniques. There’s loads of nuggets throughout the podcast, but around the 47 minute mark he goes into a bit more detail about San Millan’s training philosophy.
80% of max HR would be about 75% of VO2max, so there’s that.
The difference between Coggan’s training zones and IF may also be adding to some of the confusion.
Is this the podcast where JV “slightly” criticises San Millans approach as too zone 2 centric? And lacking sufficient glycolytic elements?
JV brought SM into Garmin(-Slipstream?) years ago. Perhaps SM has evolved since then and has introduced more upper work. Who knows. The non-z2 training is an unknown with him for sure.
Yep, and his explanation makes complete sense, but I also don’t think San Millan is doing purely “high Z2” as JV seems to imply. JV’s argument is that too much Z2 blunts the ability to tap into your “turbo”(glycolitic efforts). He touches on some of his experiences of implementing this training protocol with a couple of his riders. The bit where he talks about the use of cortisol as training shortcut is pretty interesting, too.
perhaps he was in his days with Garmin-Slipstream, who knows
Have just listened to the podcast again and it’s pretty clear JV is talking about an outdated protocol. Right at the end he states that San Millan preaches only Z2(“he’s a zealot”) 
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@Berggeiss @sryke My interpretation of JV comments was that he was making a larger point about phenotype, not so much as a criticism of the San Millan model.
He states at the time he was “quite enamored” with San Millan. He states that he might have over-prescribed this type of training for a rider like Joe Dombrowski. In doing so, a rider like that might not be able to respond when a larger, relatively short powerful effort was necessary (a cross-wind during race). Colby Pearce agrees with the need to account for “rider type”/phenotype with a story about Phil Gaimon.
JV goes on to say that for his two Dutch riders (at the time) that this type of training “…was perfect” (~55:00-58:00). So basically, too much of a good thing might not be a good thing. 
…depending on the type of rider.
Your second group of images of Pogacar rides in Pro/Elite training seems to imply that races themselves provide a lot of this non-Z2 training. Might I be putting too much emphasis on that? 
From the Training Peaks article we see that once the season starts he doesn’t prescribe as much of his “high Zone 2”. What I take from that is that this “high Z2” isn’t “recovery” or “world class XC skier walking up a hill pace”, as you state. It causes some muscular fatigue (among other things).
@Berggeiss Agree. That or JV may have oversimplified or put his own twist on the approach. We don’t really get that from his words.
You can see from Pogacar’s training once the season starts includes a good bit of intensity (images @sryke posted in Pro/Elite Training thread where @sryke states “…can see that racing is so important”.