Addition of protein and amino acids to carbohydrates does not enhance postexercise muscle glycogen synthesis

Ingestion of a protein-amino acid mixture (Pro; wheat protein hydrolysate, leucine, and phenylalanine) in combination with carbohydrate (CHO; 0.8 g.kg (-1).h(-1)) has been shown to increase muscle glycogen synthesis after exer cise compared with the same amount of CHO without Pro. The aim of this stud y was to investigate whether coingestion of Pro also increases muscle glyco gen synthesis when 1.2 g CHO.kg(-1).h(-1) is ingested. Eight male cyclists performed two experimental trials separated by 1 wk. After glycogen-depleti ng exercise, subjects received either CHO (1.2 g.kg(-1).h(-1))or CHO+Pro (1 .2 g CHO.kg(-1).h(-1) + 0.4 g Pro.kg(-1).h(-1)) during a 3-h recovery perio d. Muscle biopsies were obtained immediately, 1 h, and 3 h after exercise. Blood samples were collected immediately after the exercise bout and every 30 min thereafter. Plasma insulin was significantly higher in the CHO+Pro t rial compared with the CHO trial (P < 0.05). No difference was found in pla sma glucose or in rate of muscle glycogen synthesis between the CHO and the CHO+Pro trials. Although coingestion of a protein amino acid mixture in co mbination with a large CHO intake (1.2 g.kg(-1).h(-1)) increases insulin le vels, this does not result in increased muscle glycogen synthesis.