It is nothing in comparision in fatigue in my opinion. 3x30 is hard day (on saturday I have done 100 min TiZ@90%) and even if I was tired, even 5h z2 is more fatigue for me. My conclusion is only rpe based. When it comes to WKO TiS score it was only 8 in aerobic when 5h z2 would be probably 9 or 10 for me. 3.5h z2 (0.65-7IF) were 10s aerobic. So I would say anything that is more you have done before? 
I bet a lot of coaches donât like TR.
I did not mean to compare single workout but extended period of doing those kinds of workouts:
- with Z2, you can repeat it frequently because you need to recover only physically
- but with Z3+, it affects also central nervous system i.e. reason why we should limit number of hard days per week
For me, they could have copy/pasted random code snippets from stackoverflow and having a student glueing it together until it stops crashing and calling that HAL 11000. Who cares? Either it makes me faster or it doesnât.
Probably. But does one (long+slow versus short+fast) makes you faster than the other?
Me feeling is that by today this is an unanswered question.
From November I plan on trying a new approach for me to build my base. Week rides will be Z2 around LT1 60-90min. When time for longer rides I will do them at 60-65%. I will track TSS, TiS and also just use RPE to manage fatigue. See what kind of volume works for me.
I will evaluate what a block like this will do for meâŚAfter that an extensive aerobic base block with some tempo, SSt, work. And then an intensive aerobic block.
I could start a separate topic for this. A kind of a blog to follow a base/Z2/LT1/tempo approach?
I think if you could find a world-class pro athlete who had 30 hours a week to train but only actually did 12 hours a week with more intensity then the question would be unanswered.
Until you find that athlete, the question is answered. Probably.
Its not either-or. You need to do both.
However, you donât need to have separate shorr, hard sessions, and long easy rides. You can include those hard intervals into some of your long rides.
Faster for what kind of event? Doing these rides at what part of the season? What other trade offs are involved?
If you have effectively unlimited time and motivation to train, and your goal events are long single or multi-day races, then high volume (~30 hours/week?) seems very clearly to be the optimal approach.
For the rest of usâŚit depends. If you have 7 hours/week to train then using 5 of them doing a long ride (I would avoid calling it slow - I know people who are doing long Z2 solo rides at >20mph) is almost certainly not going to make you as fast as spreading those hours across multiple 90-120 minute rides incorporating some tempo and sweetspot intervals. But even then it depends - if youâre training for an >8 hour gravel race then you need to include some rides longer than 2 hours to test out your position, nutrition, etc. If youâre training for crits or CX then maybe those longer rides simply arenât that necessary.
Weâre all working with different limiters. Time, motivation, weather, roads, etc. I train 10-12 hours/week, and am fully aware that I could use that time more effectively by cutting out some group rides and doing more structure. But I also get a lot of motivation and enjoyment from group rides, get ground down by too much structure, and know that actually if I decided to go all in on solo and structured riding then my âtraining budgetâ is no longer 10-12 hours/week, itâs more like 6-8 hours. Because I can drag myself out of bed at 5am on a dark and chilly tuesday morning to join some mates for a 2 hour group ride, but doing that consistently to go ride 2 hours of sweetspot intervals on my own is beyond me. So for me, doing more volume by incorporating more of the riding I enjoy is a better and more sustainable approach (which makes me faster in the long term) than trying to incorporate more of the riding which theoretically will make me faster (but wonât actually make me faster because Iâll end up not doing it!).
Define âfasterââŚalso, âit dependsâ.
Somewhat tongue-in-cheek, but also somewhat serious response.
You can get âfasterâ short-term by focusing on higher intensity workouts. You can get âfasterâ long-term by building a bigger aerobic engine by focusing on longer, slower rides.
Or you can do bothâŚwhich is another somewhat tongue-in-cheek, but also somewhat serious response. The biggest issue here is the false dilemma presented - it is not a binary choice and you need both to build a successful aerobic engine.
For how long, 4 min effort or a 24 hour effort?
âIt is an important but unsolved question which type of training is most effective: to maintain a level representing 90% of the maximal oxygen uptake for 40 min, or to tax 100% of the oxygen uptake capacity for 16 min.â
- Per-Olof Ă strand
Unanswered then. And now.
The answer is⌠BOTH.
The 100% for 16 min is a race. 90% for 40 min is training.
You need both to be your best. It isnât one or the other.
Slightly different take we think we need both because we actually donât know. Therefore, we do both. It is a question that can never be answered with any certainty. It is the exploration of this question that gives you some of the answers.
16 min can be training. 40 min can be a race. The numbers/durations are not to be taken literally.
Itâs basically what @Power13 stated above, but terse and eloquently written.
Thatâs a good quote and a valid point (at least at the individual level).
However, I think it is important to keep in mind that Ă strandâs focus was very much on VO2max, since at the time it was considered the primary determinant of performance. Based on what we know now, I think you would find that most exercise physiologists would argue that 90% for 40 min would be better for improving muscular metabolic fitness (a.k.a., âlactate thresholdâ), whereas 100% for 16 min would be better for improving cardiovascular fitness (i.e., VO2max). When/how often/even if you do one or the other (or both) then comes down to the particulars, i.e., the athlete, their chosen event, etc.
Big picture, I think that George Sheehan had it right when he said that we are all an experiment of one. There are some questions that science isnât really capable of definitively answering, with âwhat is the perfect training plan?â being one.
âŚso youâre saying the one is better than the other? 
Right.
To me, these statements and axioms we throw around (âyou need bothâ, etc.), which I have parroted myself, are valid, but they can also be obvious and not helpful (e.g., âmost riding/running is below [fill in whatever level of intensity fits your world view]ââŚduh). Across the (endurance athlete) population, we need all of it. Those sort of platitudes. Iâm trying to stay away from the more triggering ones, since Iâm participating in a community that very much favors HIIT.
Yep. Thatâs what I was taught, at least. And this is sort of my point with my overly philosophically sounding ââŚexploration of that questionâ statement. Ex phys eventually got to this understanding. But I think it is still a good way to articulate the training dilemma of the individual. IOW, at any given stage, what training would be best for me, etc.?
What tends to happen with these discussions is we get into some useful particulars (like the title of the thread) and then someone comes along and rants about Rome, or Tokyo (lately, since you and Joyner appeared on Inside Science), or the training of Paula Radcliffe vs. any Scandinavian skier ever (recent past), or that speed skater dude who seemed to make all the âcampsâ happy with how he trains. Seems like everyone exclaimed âsee, heâs doing what I say you should doâ, after they cherry picked some aspect of his training. His training in the build up to his medal was extraordinarily individual to him.
We conflate what we understand at the population level with what will work for us as individuals. We do it ALL THE TIME around here. My motivation for posting was to maybe steer some of the discussion back to particulars.
Those old Runners World articles were the best.
Too much of this.
Not enough this.
When the rubber meets the road, what sorts of questions are ppl asking or determinations are they making to decide âok today I ride my bike 40 mins at threshold then dilly-dally around in some zoneâ versus, âok today I need to make my mouth bleed by making sure Iâm above 90% of the science number on my trainerâ. 
I have to disagree here since, usually when such statements are offered, it is in response to the âwhich is betterâ type question.
So âyou need bothâ and âit dependsâ arenât necessarily obvious and can be very helpful since it is not an either / or scenario (you need both) or it varies depending on objectives (it depends);;
Iâm actually agreeing with you but I think weâre doing that thing where one of us thinks weâre not. Iâll try one more time.
"in depends* or âyou need bothâ = across the entire spectrum of endurance athletes, this is always true (and therefore never helpful, but hopefully gets ppl away from â80/20â type thinking, that couldnât hurt)
Yes, I need both, but right now which is better <â productive question, IMO
The particulars of how this plays out on a case by case (training stage/block) basis is very often NOT " you need both" or âit dependsâ. You have recent results, recent history, WKO numbers, a goal, target, etc. In those cases, âwhich is betterâ can very much be answered (or theyâre going to have to be answered because you have to decide how fast to ride your bike today). If that is the context, they yeah, ask the questions to drive to a decision.
My experience with such questions is not the above scenario (usually). People want someone to tell them which training philosophy is going to work for them and whyâŚand then turn around and second guess it. Because, âit all worksâ. No it doesnât. Thatâs not what they mean.
Training is simple. People make it complicated.