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Børsheim, E1; Cree, M1; Tipton, K D.1; Elliott, T A.1; Aarsland, A1; Wolfe, R R.1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S344
G-15T Free Communication/Poster Protein Metabolism

1Shriners Hospital for Children/UTMB, Galveston, TX. E-mail:

Intake of amino acids (AA), or AA and carbohydrate, improves the net balance between muscle protein synthesis (PS) and protein breakdown (PB) to positive values after resistance exercise. The independent effect of carbohydrate on muscle protein metabolism after resistance exercise is not clear.

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To determine the effect of ingestion of a bolus of 100 g of carbohydrates on net muscle PS after resistance exercise.

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Two groups of eight subjects participated in the study. Each subject was studied once. Subjects performed a resistance exercise bout consisting of 10 sets of 8 repetitions of leg presses at 80% of their one-repetition maximum. After exercise, they rested in bed for four hours. One group (CHO) received a drink consisting of 100 g of carbohydrates (maltodextrin) 1 h after the end of exercise. The other group (PLA) received a placebo drink with an artificial sweetener instead. Leg amino acid metabolism was determined by combining infusion of 2H5- or 13C6-phenylalanine (PHE) with blood samples from femoral artery and vein, and muscle biopsies from vastus lateralis.

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Drink intake did not affect arterial insulin concentration in PLA, whereas insulin increased several-fold after the drink in CHO (p < 0.05 vs. PLA for 2.5 h). Arterial PHE concentration did not differ between groups in the period after drink. Net muscle protein balance did not change during the recovery period in PLA, whereas it improved in CHO from - 19 ± 5 nmol · ml−1 · 100 ml leg−1 before drink to an average of −4 ± 4 and 0 ± 3 nmol · ml−1· 100 ml leg−1 during the second and third h after intake of drink, respectively (p < 0.05 vs. PLA). The difference in net balance was mostly due to a suppression of PB over time in the CHO group.

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Ingestion of carbohydrate improves net muscle protein balance following resistance exercise. However, the effect is small and delayed compared to previous reported effect of intake of amino acids. Supported by NIH Grant DK 38010.

©2003The American College of Sports Medicine