High volumes of “best aerobic effort” is the hallmark of many a successful endurance athlete.
IOW, there’s nothing new or magical about what ISM apparently advocates.
You also don’t need to measure blood lactate to figure out what that intensity is - just go as hard as you can for several hours while still being able to back it up multiple days in a row. If you can’t, you’re going too hard (or not eating enough carbs), whereas if you can do it every day, you’re not going hard enough.
“best aerobic effort” - Yep, good Lydiard term. So again, what exactly would that be?
I know. Let’s just go home.
What I said/what Lydiard said: as hard as you can go for a long time while still being able to back up the effort on subsequent days.
You’d be better served by just hitting the road and just doing some good ol’fashioned endurance training.
I missed that chapter, damn.
I get if everyone rolled their eyes with my question about volume. It was specific to my situation and I can see how it came across as selfish. However, I’d argue the vast majority of us using TR can’t put in 18hrs a week, and if this protocol requires “high” volume it’s not ideal for most.
The first 100 posts are mostly concentrated discussion about finding the “magic” zone, but surely volume is an important side of this Z2 equation right?
I think the magic zone is the combination of volume and intensity in “Zone 2”
I ride 9-10hrs a week with a mix of indoor and outdoor sessions. My approach seems similar to ISM “Zone 2” , but not sure about non-Z2/intensity. That’s my main motivation for participating in this discussion. My training has been extraordinarily positive with some caveats
Everybody asks for coaching advice on this forum. I absolutely did not roll my eyes. 
It was a misguided attempt to keep us on-topic and give you the best chance of having your question discussed.
Volume is important for all training systems.
To your point though, ISM has come out and said (paraphrasing) “you think you can take shortcuts by adding intensity, doesn’t work that way”. (See higher up in the thread)
The minimum effective dose is an important aspect here. Volume alone is not the factor, it is acutally the duration of individual workouts. There is some consensus that for vo2max work at least 20min work-time are required. For “real” threshold 30-60min total work-time. For zone2/or-whatever-@AeT? You have to fatigue your muscle motor units long enough. There is no real short cut. You have to put in the miles. And (elite) cyclists can do this because of the non-weight-bearing nature of the exercise. Compared to elite runners mitchondrial density is much higher in elite cyclists. Volume and duration. The two factors here. Add frequency, just once a week will not cut it. Therefore, a minimum number of hours will probably be necessary. To build this base these 3-4 sessions seem to be just about right. Less does not build anymore, the overall stress is to low. Multiply by at least 3h (no coasting and so). Lets say this model may make sense above 10h per week. Trainings status has to be factored in as well.
HOwever, even with less time basic endurance building has its place. The benefits are probably not the great, though.
ISM on the Peter Attia podcast says 75mins is a good duration at the 1.3 - 1.8 bla. intensity.
That’s would be a session where you would feel like you had trained but not that you were exhausted.
He says 3-4 times per week during the prep phase and maintenance of 1-3 when racing. He likes the polarised model.
He always says that carbohydrate is crucial and if glycogen is low then muscle damage and overtraining will occur.
75min for whom? Beginners, moderately or well trained, Pog? All?
Good question. He does not go into the specifics. But looking at Pogacars training you can see he does blocks of this intensity that add up to 60-120 mins within a longer ride. One of the sessions is a straight 4 hours but this may be a test session (?) or a very very hard ride.
I think for a well trained amateur 75 mins is enough to get a training effect. (Opinion only)
But I assume it depends. Maybe if you have longer you stay towards the bottom on the range. And also you should be able to recover from this 4 times per week and throw in 2 maybe higher intensity session.
Gets back be that best aerobic pace that Lydiard talks about.
@Kipstrong If it’s Lydiard’s “best aerobic pace” why would you need to turn it into intervals? I’m currently thinking it’s a bit harder than this (my little 2 mmol/L pace is harder than what I’m supposed to feel for “best aerobic pace”), but I could be doing it wrong.
I do wonder if you can pre-fatigue your legs with some higher-intensity intervals (up to threshold maybe?) before the endurance workout. Or even with a run or some lifting work? Maybe no sprints though?
Intervals as running tends to be shorter duration.
If your doing 3 hours you might to 3 x 30 mins at 1.3 to 1.8bla. And easier between on the bike.
From lactate testing I’ve done on myself and others, 2mmol is close to sweetspot, so 1.3 to 1.8 mmol is pressing on a bit.
These are just my observations.
Thanks for the reference, I’ll give this a listen…
Old article, and I’m not sure I’d come to the same conclusions now with new understanding, but I probably read the same literature to come to a recommendation of ~80min Aerobic volume as a minimum for hormonal response. The studies were on endurance-trained males and team-sport (soccer) female athletes, if I recall correctly
In terms of 75min for whom? To re-pose the question, it’s more about how long can you sustain the target workload/intensity before your body starts to lose metabolic homeostasis… which is to say, how long until metabolic perturbations stimulate adaptations? Basically that Lydiard “best aerobic effort” as @old_but_not_dead_yet brought up (which might be informative, but sounds uncomfortable 
and I don’t think is necessary).
Let’s say at 65% VO2max, power under Aet, properly fueled, etc. I feel pretty good for 2hrs. 3hrs I’m starting to feel tired. 4hrs I’m gonna be pretty cracked when I get home. That probably means a 90min ride won’t give me much adaptive benefit. Might be considered a recovery or maintenance ride. 2-3hrs might be where I start to get an adaptive stimulus. And maybe 4hrs gives me a big boost, but also fatigues me so that I need to recover or go easier the next day(s).
There is an elegant model of how duration relative to TTE (time to exhaustion) affects training load, adaptive benefit, and recovery required.
Once again, let’s not get too preoccupied with over-precise targets (" That means I need to spend at least 2:15:00 at 189W to get any benefit" 
) And let’s just appreciate that the stimulus (intensity x duration) we need to improve is related to the chronic stimulus that our bodies are currently capable of and adapted to. Might be 75min for some, might be 25min or 125min for others.
Try this
Part one is also good but could not find it .
I don’t know to what hormonal responses you are alluding, but it isn’t really relevant, because the signals for adaptation to exercise are local, not humoral, in nature.
Agreed, handwavy ‘hormonal responses’ isn’t the point. But here’s one of the articles at least
