Plasma amino acid responses of trained athletes to two successive exhaustion trials with and without interim carbohydrate feeding.

The purpose of this research was to measure changes in selected plasma amino acids (AA) during two successive exercise trials to exhaustion. Eleven trained male athletes completed these trials at weeks 4, 6, 8 and 12. Blood samples for each test were collected after a 12-hour fast at times (in minutes) 0 (Resting), 45, 90, 135, 180, at exhaustion (EI), after a 20-minute recovery period, and at the second exhaustion (EII). At the end of EI, subjects consumed an artificially sweetened water replacement (placebo) treatment or a carbohydrate (CHO) replacement (1.1 g CHO/kg BW) in order to determine any effect of CHO replacement on changes in energy substrates or AA, adjusted for plasma volume changes. From baseline to EI, alpha-aminobutyric acid, alanine, glycine, isoleucine, serine, valine threonine, and tyrosine decreased significantly (p less than or equal to 0.05), while taurine increased significantly. During the recovery period following EI, isoleucine, leucine, ornithine, phenylalanine, tyrosine, urea ...