Where does volume enter in?
4 reps to failure with 160lbs
how many 2 rep sets with 160lbs to equal the adaptive response of that single set? My guess is at least 3. All done with the same %RM.
You cannot equate volume to response without accounting for momentary capacity expended.
A single set to an 8RM is more intense than four 2 reps sets using your 6RM. Four 2 reps sets with your 4RM will be more intense than the 8RM to failure, but eight singles with your 4RM will probably not. There's an intersection of volume and intensity with different loads, but it can't all be adequately described using only %RM. In this case we're using the same rep count across differing %RM and still not getting the same level of effort.
Though it is an easy way to generalize, which is super helpful in open discussions.
This makes me think of how cats can engage all their muscle instantaneously. Humans I think take like 30sec which fatigues some muscle before others even start. Cats can jump over and over every day. If they can engage all their muscle in 1 sec and do it thirty times would they have the same muscle fatigue as a human taking 30sec to lift once.
Does lifting speed have a higher relationship to fatigue than load but we only observe that time difference due to the load? How does one train speed of engagement without the fatigue from time under tension? Is this why some loads are sweet spots?
Volume is a different variable. There is always intensity and volume. Volume is not as simple as intensity and I find it better to be explained in much more detail in order to be meaningful in a discussion.
I don't like using words such as "intense" in a discussion like this, because it precisely can mask a simple term like intensity. How about calling a set hard?
If I knew the exact answer to 3*5 @ 80% Vs 5*3 @ 85% I'd love to enlighten the world but now I can all but theorize.
In short, I think it's the best to do as much volume in as high intensity as your recovery capabilities and life demands allow, that is if you seek maximal strength development.
If in doubt, lift. Still in doubt? Lift more.
To me, you reach a point where intensity of effort hampers volume.
There is an inverse point where lack of intensity of effort renders a lot of the volume adaptively pointless, regardless of %rm at anything under 95 - 100%.
I agree though, there has to be a starting point and %rm is the least subjective variable. But is still only a starting point.