It seems as though post-exercise protein combined with carbohydrates does nothing to enhance protein synthesis. However when combined with leucine, there is a significant difference.
Am J Physiol Endocrinol Metab. 2007 Jul 3
Co-ingestion of carbohydrate with protein does not further augment post-exercise muscle protein synthesis.
The present study was designed to assess the impact of co-ingestion of various amounts of carbohydrate combined to an ample amount of protein intake on post-exercise muscle protein synthesis rates. Ten healthy, fit men (20+/-0.3 y) were randomly assigned to 3 cross-over experiments. After 60 min of resistance exercise, subjects consumed 0.3 g.kg(-1).h(-1) protein hydrolysate with 0, 0.15, or 0.6 g.kg(-1).h(-1) carbohydrate during a 6 h recovery period (PRO, PRO+LCHO, and PRO+HCHO, respectively). Primed, continuous infusions with L-[ring-(13)C6]phenylalanine, L-[ring-(2)H2]tyrosine, and [6,6-(2)H2]glucose were applied, and blood and muscle samples were collected to assess whole-body protein turnover and glucose kinetics as well as protein fractional synthesis rate (FSR) in the vastus lateralis muscle over 6 h of post-exercise recovery. Plasma insulin responses were significantly greater in PRO+HCHO compared to PRO+LCHO and PRO (18.4+/-2.9 vs. 3.7+/-0.5 and 1.5+/-0.2 U.6h.L(-1), respectively: P<0.001). Plasma glucose rate of appearance (Ra) and disappearance (Rd) increased over time in PRO+HCHO and PRO+LCHO but not in PRO. Plasma glucose Ra and Rd were substantially greater in PRO+HCHO vs both PRO and PRO+LCHO (P<0.01). Whole-body protein breakdown, synthesis and oxidation rates, as well as whole-body protein balance did not differ between experiments. Mixed muscle FSR did not differ between treatments and averaged 0.10+/-0.01, 0.10+/-0.01 and 0.11+/-0.01 %.h(-1) in the PRO, PRO+LCHO and PRO+HCHO experiments, respectively. In conclusion, co-ingestion of carbohydrate during recovery does not further stimulate post-exercise muscle protein synthesis when ample protein is ingested. http://www.ncbi.nlm.nih.gov/sites/en...ubmed_RVDocSum
Am J Physiol Endocrinol Metab 288: E645-E653, 2005.
Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects
The present study was designed to determine postexercise muscle protein synthesis and whole body protein balance following the combined ingestion of carbohydrate with or without protein and/or free leucine. Eight male subjects were randomly assigned to three trials in which they consumed drinks containing either carbohydrate (CHO), carbohydrate and protein (CHO+PRO), or carbohydrate, protein, and free leucine (CHO+PRO+Leu) following 45 min of resistance exercise. A primed, continuous infusion of L-[ring-13C6]phenylalanine was applied, with blood samples and muscle biopsies collected to assess fractional synthetic rate (FSR) in the vastus lateralis muscle as well as whole body protein turnover during 6 h of postexercise recovery. Plasma insulin response was higher in the CHO+PRO+Leu compared with the CHO and CHO+PRO trials (+240 ? 19% and +77 ? 11%, respectively, P < 0.05). Whole body protein breakdown rates were lower, and whole body protein synthesis rates were higher, in the CHO+PRO and CHO+PRO+Leu trials compared with the CHO trial (P < 0.05). Addition of leucine in the CHO+PRO+Leu trial resulted in a lower protein oxidation rate compared with the CHO+PRO trial. Protein balance was negative during recovery in the CHO trial but positive in the CHO+PRO and CHO+PRO+Leu trials. In the CHO+PRO+Leu trial, whole body net protein balance was significantly greater compared with values observed in the CHO+PRO and CHO trials (P < 0.05). Mixed muscle FSR, measured over a 6-h period of postexercise recovery, was significantly greater in the CHO+PRO+Leu trial compared with the CHO trial (0.095 ? 0.006 vs. 0.061 ? 0.008%/h, respectively, P < 0.05), with intermediate values observed in the CHO+PRO trial (0.0820 ? 0.0104%/h). We conclude that coingestion of protein and leucine stimulates muscle protein synthesis and optimizes whole body protein balance compared with the intake of carbohydrate only.
In conclusion, the combined ingestion of protein and leucine with carbohydrate improves whole body protein balance during recovery from resistance exercise compared with the ingestion of carbohydrate or carbohydrate with protein. The combined ingestion of both leucine and protein with carbohydrate augments postexercise mixed muscle protein synthesis compared with the ingestion of only carbohydrate. The present data indicate that the additional ingestion of free leucine in combination with protein and carbohydrate likely represents an effective strategy to increase muscle anabolism following resistance exercise. http://ajpendo.physiology.org/cgi/co.../4/E645?ck=nck