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Preexercise Aminoacidemia and Muscle Protein Synthesis after Resistance Exercise

BURKE, LOUISE M.1; HAWLEY, JOHN A.2; ROSS, MEGAN L.1; MOORE, DANIEL R.3,4; PHILLIPS, STUART M.4; SLATER, GARY R.1; STELLINGWERFF, TRENT3; TIPTON, KEVIN D.5; GARNHAM, ANDREW P.6; COFFEY, VERNON G.2

Medicine & Science in Sports & Exercise: October 2012 - Volume 44 - Issue 10 - p 1968–1977
doi: 10.1249/MSS.0b013e31825d28fa
Applied Sciences

Purpose: We have previously shown that the aminoacidemia caused by the consumption of a rapidly digested protein after resistance exercise enhances muscle protein synthesis (MPS) more than the amino acid (AA) profile associated with a slowly digested protein. Here, we investigated whether differential feeding patterns of a whey protein mixture commencing before exercise affect postexercise intracellular signaling and MPS.

Methods: Twelve resistance-trained males performed leg resistance exercise 45 min after commencing each of three volume-matched nutrition protocols: placebo (PLAC, artificially sweetened water), BOLUS (25 g of whey protein + 5 g of leucine dissolved in artificially sweetened water; 1× 500 mL), or PULSE (15× 33-mL aliquots of BOLUS drink every 15 min).

Results: The preexercise rise in plasma AA concentration with PULSE was attenuated compared with BOLUS (P < 0.05); this effect was reversed after exercise, with two-fold greater leucine concentrations in PULSE compared with BOLUS (P < 0.05). One-hour postexercise, phosphorylation of p70 S6Kthr389 and rpS6ser235/6 was increased above baseline with BOLUS and PULSE, but not PLAC (P < 0.05); furthermore, PULSE > BOLUS (P < 0.05). MPS throughout 5 h of recovery was higher with protein ingestion compared with PLAC (0.037 ± 0.007), with no differences between BOLUS or PULSE (0.085 ± 0.013 vs. 0.095 ± 0.010%·h−1, respectively, P = 0.56).

Conclusions: Manipulation of aminoacidemia before resistance exercise via different patterns of intake of protein altered plasma AA profiles and postexercise intracellular signaling. However, there was no difference in the enhancement of the muscle protein synthetic response after exercise. Protein sources producing a slow AA release, when consumed before resistance exercise in sufficient amounts, are as effective as rapidly digested proteins in promoting postexercise MPS.

1Sports Nutrition, Australian Institute of Sport, Canberra, ACT, AUSTRALIA; 2Health Innovations Research Institute, School of Medical Sciences, RMIT University, Victoria, AUSTRALIA; 3Nestlé Research Center, Nestec Ltd., Lausanne, SWITZERLAND; 4Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, Hamilton, Ontario, CANADA; 5School of Sport, University of Stirling, Stirling, SCOTLAND; and 6School of Health Sciences, Deakin University, Burwood, Victoria, AUSTRALIA

Address for correspondence: Louise M. Burke, Ph.D., Sports Nutrition, Australian Institute of Sport, PO Box 176, Belconnen ACT 2616, Australia; E-mail: louise.burke@ausport.gov.au.

Submitted for publication September 2011.

Accepted for publication April 2012.

©2012The American College of Sports Medicine