Background & aimsHyperaminoacidemia stimulates myofibrillar fractional synthesis rate (myoFSR) transiently in resting skeletal muscle. We investigated whether light-load resistance exercise can extent this responsiveness.MethodsTen 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 [1-13C]-leucine incorporation. Muscle biopsies were obtained from the resting (REST) and exercised (EXC) muscles every 2.5-h in the protein-fed period.ResultsProtein 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 μmol L−1 and 854 ± 35 μmol 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).ConclusionsCompared 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.
Clinical Nutrition, 2012, Vol 32, Issue 2, p. 236-44