Things you probably know:
- Leucine is the key amino acid responsible for stimulating muscle protein synthesis.
- Leucine doses of approximately 0.05 to 0.06 grams per kilogram of body weight are sufficient to maximally stimulate muscle anabolism.
But researchers from the University of Texas at Galveston have uncovered something you may not know: the duration of this anabolic response appears to only last 2-3 hours, even when leucine levels (and other essential amino acids) in blood remain elevated.
The reason? My hunch is that this "refractory nature" of the anabolic response is causally linked to insulin signaling. If I'm correct, there are two options to try and fix this problem, extend the anabolic response, and pack more muscle onto your frame.
First, you can use an insulinogenic carbohydrate (or similar ingredients) peri- and post-exercise to bump insulin concentrations into the range considered "permissive" for stimulating muscle growth.
Second, you can provide ingredients that improve various aspects of the insulin signaling pathway itself, like a water-soluble cinnamon extract, 4-hydroxyisoleucine, and alpha lipoic acid.
I'm speculating, but when used concurrently with a blend of essential amino acids, particularly those weighted heavily with leucine, it's the best way I know of to increase functional lean mass. This is the underlying concept of "protein pulsing" with Biotest's casein hydrolysate, which attempts to maximally stimulate insulin and plasma essential amino acids (particularly leucine) at the same time.