Send to

Choose Destination
Med Sci Sports Exerc. 2015 Mar;47(3):547-55. doi: 10.1249/MSS.0000000000000447.

Protein-leucine fed dose effects on muscle protein synthesis after endurance exercise.

Author information

1School of Sport and Exercise, Massey University, Wellington, NEW ZEALAND; 2Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, AUSTRALIA; 3Kinesiology, McMaster University, Hamilton, CANADA; 4The Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL; 5Nestle Research Centre, Lausanne, SWITZERLAND; 6Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, ON, CANADA; and 7Canadian Sport Institute-Pacific, Victoria, BC, CANADA.


Protein-leucine ingestion after strenuous endurance exercise accentuates muscle protein synthesis and improves recovery of muscle performance.


The objective of this study is to determine whether a low-dose protein-leucine blend ingested after endurance exercise enhances skeletal muscle myofibrillar protein fractional synthetic rate (FSR).


In a crossover design, 12 trained men completed 100 min of high-intensity cycling, then ingested either 70/15/180/30 g of protein/leucine/carbohydrate/fat (15LEU), 23/5/180/30 g of 5LEU, or 0/0/274/30 g of CON beverages in randomized order in four servings during the first 90 min of a 240-min recovery period. Muscle biopsies were collected at 30 and 240 min into recovery with FSR determined by L-[ring-13C6]phenylalanine incorporation and mTORC1 pathway phosphorylation by Western blot.


The 33% (90% CL, ±12%) increase in FSR with 5LEU (mean, SD: 0.080, 0.014%·h(-1)) versus CON (0.060, 0.012%·h(-1)) represented near-maximal FSR stimulation. Tripling protein-leucine dose (15LEU: 0.090, 0.11%·h(-1)) negligibly increased FSR (13%, ±12% vs 5LEU). Despite similar FSR, mTORC1(Ser2448) phosphorylation only increased with 15LEU at 30 min, whereas p70S6K(Thr389), rpS6(Ser240/244), and 4E-BP1γ(Ser112) phosphorylation increased with protein-leucine quantity at one or both time points. Plasma leucine and essential amino acid concentrations decreased during recovery in CON but increased with protein-leucine dose. Serum insulin was increased in 15LEU versus CON (60%, ±20%) but was unaffected relative to 5LEU. Regression analysis revealed p70S6K-rpS6 phosphorylation moderately predicted FSR, but the associations with plasma leucine and essential amino acids were small.


Ingesting 23 g of protein with 5 g of added leucine achieved near-maximal FSR after endurance exercise, an effect unlikely attributable to mTORC1-S6K-rpS6 signaling, insulin, or amino acids. Translating the effects of protein-leucine quantity on protein synthesis to optimizing adaptation and performance requires further research.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Wolters Kluwer
Loading ...
Support Center