Low Muscle Glycogen Concentration Does Not Suppress the Anabolic Response to Resistance Exercise.
J Appl Physiol. 2012 May 24. Epub 2012 May 24. PMID: 22628371
We determined the effect of muscle glycogen concentration and post-exercise nutrition on anabolic signaling and rates of myofibrillar protein synthesis after resistance exercise (REX). Sixteen young, healthy males matched for age, body mass, peak oxygen uptake (VO(2peak)) and strength (one repetition maximum; 1RM) were randomly assigned to either a nutrient or placebo group. After 48 h diet and exercise control, subjects undertook a glycogen-depletion protocol consisting of one-leg cycling to fatigue (LOW), while the other leg rested (NORM). The next morning following an overnight fast, a primed, constant infusion of L-[ring-(13)C(6)] phenylalanine was commenced and subjects completed 8 sets of 5 unilateral leg press repetitions at 80% 1RM. Immediately after REX and 2 h later, subjects consumed a 500 mL bolus of a protein/CHO (20 g whey + 40 g maltodextrin), or placebo beverage. Muscle biopsies from the vastus lateralis of both legs were taken at rest and 1 and 4 h after REX. Muscle glycogen concentration was higher in the NORM than LOW at all time points in both nutrient and placebo groups (P<0.05). Post-exercise Akt-p70S6K-rpS6 phosphorylation increased in both groups with no differences between legs (P<0.05). mTOR(Ser2448) phosphorylation in placebo increased 1 h after exercise in NORM (P<0.05) while mTOR increased ~4 fold in LOW (P<0.01) and ~11 fold in NORM with nutrient (P<0.01; different between legs P<0.05). Post-exercise rates of MPS were not different between NORM and LOW in nutrient (0.070± 0.022 vs. 0.068 ± 0.018 %(.)h(-1)) or placebo (0.045 ± 0.021 vs. 0.049 ± 0.017 %(.)h(-1)). We conclude that commencing high-intensity REX with low muscle glycogen availability does not compromise the anabolic signal and subsequent rates of MPS, at least during the early (4 h) post-exercise recovery period.