When I said middle of the muscle I was just making it easy to understand.
Muscle fibers work only on or off, there is no middle ground, when you lift light you are not using all the muscle fibers, only by lifting your 1rep max are you using 100% of your muscle. Obv we can do this all the time so we do 3-6 with a lighter weight.
2-6 is most benifitial for muscle growth, The only reason we go for other ranges 6-8, 10-15 etc... is just as you said, to mix it up and throwing off the Equilb of ATP replenishment. However 2-6 is where we make our biggest gains. In the higher rep ranges the muscle does increase in size but it deflates after a few hours.
"WHAT? You're saying that by not training type 1 fibers, they will just be able to sustain a muscular contraction over a long period of time because you are strong or "fit"?"
Type 1 fibers are still trained with 3-6reps, more so with a 1second eccentric and 4second consentric count.
Im just trying to make the point that you cant put a number on "this many reps do this and tat many reps do that"
There are all these numbers in books, but at the end of the day its all to do with
1, are you really lifting the most you can for your reps.
2, how fast your doing your reps.
what will work a) type 1, b) type 2 muscle fibers more...
1. 6reps - slow and controled, heavy weight, 1-4count
2. 15reps - fast, light weight, 1-1count.
PPL take what they read too Literally.