Why does linear progression end?

[Poobers]

I thought it was due to a lack of volume. But I notice the SS guys reccomend adding a deload day in between heavy squats, is this not reducing the volume?

How does recovery play into this?

Any articles you guys can point me towards that will clarify the subject?

[JoshA]

Because squatting mulitiple sets ~RPE 10 every workout requires a deload due to acumulated fatigue.
You probably shouldn't be squatting ~RPE 10 every workout so you can actually do more volume becuase higher intensities at the same rep ranges generate more fatigue (but not more adaptation or else SS would work forever).

The easiest way to think about this is that frequency cannot ever be above 7, intensity cannot be above RPE 10 (or if you want weight, whatever your max is currently), so that leaves volume which to an extent is infinately scalable. Linear progression fails because you are not increasing frequency or volume and eventually you are not increasing intensity either. The reason every beginner program works is mostly due to nueral drive (basically you send better signals to your muscles) and "practice" with the lifts leading you to be more efficient, this cannot go on forever and probably is asymptotic so after a relatively short period of training correctly, both of these factors reach diminishing returns without more stimulus being applied. From personal experience, I went from deadlifting one heavy set of 5 a week on SS to deadlifting probably something around 7-10 moderately heavy sets (RPE 6-8) on the bridge, and my deadlift went up 90lbs in 20 weeks while gaining ~6 pounds.

Programming podcasts: each is ~1hr
https://www.youtube.com/watch?v=9IEFJ_90vGE
https://www.youtube.com/watch?v=JCPAffRLtNo
https://www.youtube.com/watch?v=kI6QwgKLP0M