Carbohydrate Does Not Augment Exercise-Induced Protein Accretion versus Protein Alone

STAPLES, AARON W.1; BURD, NICHOLAS A.1; WEST, DANIEL W. D.1; CURRIE, KATHARINE D.1; ATHERTON, PHILIP J.2; MOORE, DANIEL R.1; RENNIE, MICHAEL J.2; MACDONALD, MAUREEN J.1; BAKER, STEVEN K.3; PHILLIPS, STUART M.1

Medicine & Science in Sports & Exercise: July 2011 - Volume 43 - Issue 7 - pp 1154-1161
doi: 10.1249/MSS.0b013e31820751cb
Basic Sciences

Purpose: We tested the thesis that CHO and protein coingestion would augment muscle protein synthesis (MPS) and inhibit muscle protein breakdown (MPB) at rest and after resistance exercise.

Methods: Nine men (age = 23.0 ± 1.9 yr, body mass index = 24.2 ± 2.1 kg·m−2) performed two unilateral knee extension trials (four sets × 8-12 repetitions to failure) followed by consumption of 25 g 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 in the PRO trial (P < 0.05); phosphorylations of Akt (P = 0.05) and acetyl coA carboxylase-β (P < 0.05) were greater after exercise than at rest. The concurrent ingestion of 50 g of CHO with 25 g of protein did not stimulate mixed MPS or inhibit MPB more than 25 g of protein alone either at rest or after resistance exercise.

Conclusions: Our data suggest that insulin is not additive or synergistic to rates of MPS or MPB when CHO is coingested with a dose of protein that maximally stimulates rates of MPS.

1Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, CANADA; 2School of Graduate Entry Medicine and Health, City Hospital, University of Nottingham, Derby, UNITED KINGDOM; and 3Michael G. DeGroote School of Medicine, Department of Neurology, McMaster University, Hamilton, Ontario, CANADA

Address for correspondence: Stuart M. Phillips, Ph.D., McMaster University, 1280 Main St. West, Hamilton, Ontario, Canada L8S 4K1; E-mail: phillis@mcmaster.ca.

Submitted for publication November 2010.

Accepted for publication November 2010.

© 2011 American College of Sports Medicine