The anabolic potential of dietary protein intake on skeletal muscle is prolonged by prior light-load exercise

Background & aims: Hyperaminoacidemia stimulates myofibrillar fractional synthesis rate (myoFSR) transiently in resting skeletal muscle. We investigated whether light-load resistance exercise can extent this responsiveness. Methods: Ten healthy males exercised one leg with a light-load resistance-like exercise at 16% of 1 repetition maximum and received oral protein boluses every hour for a 10-h period. Their myoFSR was determined by [1-C-13]-leucine incorporation. Muscle biopsies were obtained from the resting (REST) and exercised (EXC) muscles every 2.5-h in the protein-fed period. Results: Protein feeding significantly elevated plasma leucine and essential amino acids by an average of 39 +/- 9% (mean +/- SEM) and 20 +/- 4%, respectively, compared to the basal concentrations: 197 +/- 12 mu mol L (-1) and 854 +/- 35 mu mol L-1, respectively. The myoFSR was similar in EXC and REST muscles in the first 8 h (all time intervals p > 0.05). After 8 h the myoFSR dropped in the REST muscle to 0.041 +/- 0.005%.h(-1), which was 65 +/- 5% of the rate in EXC leg at the same time point (0.062 +/- 0.004%.h(-1)) and 80 +/- 14% of the level in REST leg from 0.5 to 8 h (0.056 +/- 0.005%.h(-1)) (interaction p < 0.05). Conclusions: Compared to rest, light-load exercise prolonged the stimulatory effect of dietary protein on muscle biosynthesis providing perspectives for a muscle restorative effect in clinical settings where strenuous activity is intolerable. (C) 2012 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.