Wednesday, April 20, 2011

More Than Protein Anabolic: Post-Workout Protein Supplementation Up-Regulates Muscle Glycogen (Re-)Synthesis, As Well.

As an avid reader of the SuppVersity, you already knew that post-workout protein supplementation increases protein synthesis via mTOR-signaling and increased AKT-phosphorylation. A study (Hara. 2011) published in the scientific journal Metabolism, only one week ago, has now established that the addition of protein to a post workout carbohydrate supplement led to significant increases in the rate of muscle glycogen re-synthesis, as well.
Figure 1: Influence of added protein (C+P, whey isolate) over carbohydrate only (CHO) supplementation on muscle glycogen 90 minutes after exhausting exercise (data adapted from Hara. 2011)
After a 3-hour swimming test, which was intended to completely deplete the rats muscle glycogen stores, the researchers fed their rats "either 0.9 g carbohydrate per kilogram body mass for the CHO group or 0.9 g carbohydrate + 0.3 g protein per kilogram body mass for the C+P groups". Just to set this into perspective, this would translate into a meager 12g carbohydrates + 4g protein for a 80kg human being! Yet, despite the comparably insignificant amount of protein, muscle biopsies from the red and white quadriceps immediately, 30 minutes, or 90 minutes postexercise revealed that
Glycogen concentration of the C+P group was greater than that of the CHO group at 90 minutes postexercise in both red (C+P, 28.3 ± 2.6 µmol/g vs CHO, 22.4 ± 2.0 µmol/g; P < .05) and white (C+P, 24.9 ± 2.4 µmol/g vs CHO, 17.64 ± 1.5 µmol/g; P < .01) quadriceps. Protein kinase B phosphorylation was greater in the C+P-30 group (the number following treatment group abbreviation refers to time [in minutes] of euthanasia following exercise) than the sedentary control and exercised control groups in red quadriceps at 30 minutes and in white quadriceps at 90 minutes postexercise. This difference was not observed in the CHO group.
With protein kinase B being responsible among other things for the GLUT4 induced uptake of glucose into the muscle cell, the addition of relatively small amounts of protein to your post-workout shake may have a direct "nutrient partitioning" effect, i.e. it will shuttle glucose into muscle not fat (or liver). Furthermore, it will shorten regeneration times, because other than in "glucose-only" animals, the quadriceps muscles of the C+P group were - at least partly - "refueled" 90 minutes after the exercise-bout.

Taken together these results underline the importance of post-workout protein supplementation, for which - you probably already guessed that - the study used a high quality whey protein isolate. Add to that the beneficial effects of protein supplementation on mTOR and muscle protein (re-)synthesis, you already read (SuppVersity) and heard (BodyRX show) about and you will understand why a quality whey protein should be the staple in the supplement regimen of anybody who wants to add a few pounds of solid muscle to his frame.