Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures.
BACKGROUND
Postexercise muscle glycogen synthesis is an important factor in determining the time needed to recover from prolonged exercise.


OBJECTIVE
This study investigated whether an increase in carbohydrate intake, ingestion of a mixture of protein hydrolysate and amino acids in combination with carbohydrate, or both results in higher postexercise muscle glycogen synthesis rates than does ingestion of 0.8 g*kg(-)(1)*h(-)(1) carbohydrate, provided at 30-min intervals.


METHODS
Eight trained cyclists visited the laboratory 3 times, during which a control beverage and 2 other beverages were tested. After the subjects participated in a strict glycogen-depletion protocol, muscle biopsy samples were collected. The subjects received a beverage every 30 min to ensure ingestion of 0.8 g carbohydrate*kg(-)(1)*h(-)(1) (Carb trial), 0.8 g carbohydrate*kg(-)(1)*h(-)(1) plus 0.4 g wheat protein hydrolysate plus free leucine and phenylalanine*kg(-)(1)*h(-)(1) (proven to be highly insulinotropic; Carb + Pro trial), or 1.2 g carbohydrate*kg(-)(1)*h(-)(1) (Carb + Carb trial). After 5 h, a second biopsy was taken.


RESULTS
Plasma insulin responses in the Carb + Pro and Carb + Carb trials were higher than those in the Carb trial (88 +/- 17% and 46 +/- 18%; P < 0.05). Muscle glycogen synthesis was higher in both trials than in the Carb trial (35. 4 +/- 5.1 and 44.8 +/- 6.8 compared with 16.6 +/- 7.8 micromol glycosol units*g dry wt(-)(1)*h(-)(1), respectively; P < 0.05).


CONCLUSIONS
Addition of a mixture of protein hydrolysate and amino acids to a carbohydrate-containing solution (at an intake of 0.8 g carbohydrate*kg(-)(1)*h(-)(1)) can stimulate glycogen synthesis. However, glycogen synthesis can also be accelerated by increasing carbohydrate intake (0.4 g*kg(-)(1)*h(-)(1)) when supplements are provided at 30-min intervals.
van Loon
L J
LJ
From the Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Department of Human Biology, Maastricht University, Maastricht, The Netherlands. L.vanLoon@hb.unimaas.nl
Saris
W H
WH
Kruijshoop
M
M
Wagenmakers
A J
AJ
D000328:Adult; D000596:Amino Acids / Q000008:administration & dosage; D001628:Beverages; D001786:Blood Glucose / Q000378:metabolism; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D005526:Food, Formulated; D006003:Glycogen / Q000096:biosynthesis*; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D011492:Protein Hydrolysates / Q000008:administration & dosage; D012016:Reference Values; D013997:Time Factors
D000596:Amino Acids; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D007328:Insulin; D011492:Protein Hydrolysates; D006003:Glycogen