I
there's more to it than just "MPS lasts for 48hr," of course
I would make a question about it.
The catabolic issue apart, I suppose that we should consider 2 factors: 1) how long MPS stays elevated; 2) how much MPS stays elevated.
Some years ago, I read a paper.
It measured MTOR after workout, comparing low and high frequency workout (the volume per session was the same while the weekly volume was, obviously, different). The study concluded that the MPS doesn't last for more than 48 hours but in the low frequency group the Mtor levels were higher compared to high frequency group. So, in the 48 hours range, in the low frequency group MPS was higher than the high frequency group (again, in 48 hours, not weekly).
I can't find the research but would like to know if u think that makes sense.
II
"more room for growth"
I describe my feeling, nothing more.
the pump after a high(er) volume session (MDT style) is better than the pump I get after a total body low(er) body training.
I don't think that pump is good per se but using "pump workout" is like creating "more room for growth" so it makes sense to me having some high volume sessions during the year.
I remember the ABCDE program guy (he had a strange sweedish name) said that the "pressure" of connective tissue is a limiting factor for muscle growth and suggested that the stretching of connective tissue (using stretching, pumping the muscle, loading the muscle with nutrient) can speed top muscle growth.