I would agree with the majority of this. But then I usually agree with what John says, he is much smarter than me and always talks sense.
Also and this isn't a direct reply to John, but more of a sweeping statement - I hope nobody thinks I am telling anyone how to train. I again have to state that. I'm giving people the option and the insight into a particular way to train that is probably the best option for most people reading this post, who are interested in running more than the average runner (they are on a running forum) they are limited on time (a lot of people will relate) and want to look long term to improve (don't we all?).
If you don't want to train everyday or you want to overload and roll the dice for a short term goal, honestly there are better ways most likely to train.
Sub threshold again, is not the only way to train. But probably around the area that'll gain you the best value for money. As I've said quite a few times, 9/10ths of the puzzle here is simply the impact and accumulation of load, no matter how you get it. Worry about the last bit, when you need to worry about the last bit. I've been doing this 2+ years now and whilst it's mentally quite boring, I still haven't had to worry about the last bit and have consistently improved. You have to account and track load somehow and measuring the impact of load, using pace as a proxy for power as I did for many years on the bike, to me l, seems like the most sensible option. It seems to have tracked incredibly well for a large % of people who have trained like this (again note, not all). The ones who have had the best improvement have tended to be the ones not getting greedy, or straying away from my philosophy of discipline and consistency.
How you get from A to B, there is no right and wrong way, but some ways are easier and some ways carry more risk. Again, I believe firstly this is probably the easiest way and also secondly the least risk (running is inherently injury risky). This probably applies from the 5k through to the marathon, albeit that required some adaptations, although less than most training plans going from the lower end of the scale of racing up to a full marathon.
Ultimately this is pretty simple, but the misomer is that once you scrape under the surface it's actually pretty complicated and you don't have much margin for error to make mistakes. I could literally write a book on it I'm sure, and then some. I think ultimately what I mean is the actual training you do is pretty damn simple, but the understanding of what you are doing and why is densely layered. Once you stray away from understanding what the actual goal is here, that's when the problems start. Maybe I'll do something to clarify it all properly at some point.
Half the problem is how this has exploded, for whatever reason. This is nobody's fault but we have gone from a little interest to almost this becoming a "thing" that I've even heard runners talking about in real life, which is crazy. People seem to hear about it and just jump in without hearing nothing more than "Norwegian Singles", think Jakob and want a piece. Where actually, this isn't really anything like that if you understand all the above. The book (that I will never write most likely ) would likely make more sense to be called the "Time Trialist's sweetspot bible" than anything to do with Jakob . But that's definitely where people mind goes to I think. The only reason really lactate got involved for me, was to use it to find the paces I could then use as a proxy for power and a % of what sweetspot sessions were on the bike. My thinking was this was to be my last throw of the dice to actually improve at running, after almost a year of banging my head against a brick wall around that high 18 mark.
The whole thing to me, is totally nuts as I only posted one morning at the start because I was bored and saw something I thought I could contribute to, whilst talking a morning sh*t.