Med Sci Sports Exerc. 2010 Dec 1. [Epub ahead of print]
Carbohydrate Does Not Augment Exercise-Induced Protein Accretion versus Protein Alone.
Staples AW, Burd NA, West DW, Currie KD, Atherton PJ, Moore DR, Rennie MJ, Macdonald MJ, Baker SK, Phillips SM.
1Exercise Metabolism Research Group, Department of Kinesiology and 2Michael G. DeGroote School of Medicine, Department of Neurology, McMaster University, 1280 Main St. West, Hamilton, ON, and 3School of Graduate Entry Medicine and Health, City Hospital, University of Nottingham, Derby, UK.
Abstract
PURPOSE: We tested the thesis that carbohydrate and protein co-ingestion would augment muscle protein synthesis (MPS) and inhibit muscle protein breakdown (MPB) at rest and after resistance exercise.
METHODS: Nine men (23.0 ± 1.9 y, BMI, 24.2 ± 2.1 kg·m) performed two unilateral knee extension trials (4 sets × 8-12 repetitions to failure) followed by consumption of 25g of whey protein (PRO) or 25 g of whey protein plus 50 g of maltodextrin (PRO+CARB). Muscle biopsies and stable isotope methodology were used to measure MPS and MPB.
RESULTS: The areas under the glucose and insulin curves were 17.5-fold (P < 0.05) and 5-fold (P < 0.05) greater, respectively, for PRO+CARB than for PRO. Exercise increased MPS and MPB (both P < 0.05), but there were no differences between PRO and PRO+CARB in the rested or exercised legs. Phosphorylation of Akt was greater in the PRO+CARB than the PRO trial (P < 0.05); phosphorylation of Akt (P = 0.05) and acetyl coA carboxylase-β (ACC; P < 0.05) were greater after exercise than at rest. The concurrent ingestion of 50g carbohydrate with 25g of protein did not stimulate mixed MPS or inhibit MPB more than 25g of protein alone either at rest or after resistance exercise.
CONCLUSION: Our data suggest that insulin is not additive or synergistic to rates of MPS or MPB when carbohydrate is co-ingested with a dose of protein that maximally stimulates rates of MPS.
