title: Independent and combined effects of liquid carbohydrate/essential amino acid ingestion on hormonal and muscular adaptations following resistance training in untrained men.
abstract: This investigation examined chronic alteration of the acute hormonal response associated with liquid carbohydrate (CHO) and/or essential amino acid (EAA) ingestion on hormonal and muscular adaptations following resistance training. Thirty-two untrained young men performed 12 weeks of resistance training twice a week, consuming ~675 ml of either, a 6% CHO solution, 6 g EAA mixture, combined CHO + EAA supplement or placebo (PLA). Blood samples were obtained pre- and post-exercise (week 0, 4, 8, and 12), for determination of glucose, insulin, and cortisol. 3-Methylhistidine excretion and muscle fibre cross-sectional area (fCSA) were determined pre- and post-training. Post-exercise cortisol increased (P<0.05) during each training phase for PLA. No change was displayed by EAA; CHO and CHO + EAA demonstrated post-exercise decreases (P<0.05). All groups displayed reduced pre-exercise cortisol at week 12 compared to week 0 (P<0.05). Post-exercise insulin concentrations showed no change for PLA; increases were observed for the treatment groups (P<0.05), which remained greater for CHO and CHO + EAA (P<0.001) than PLA. EAA and CHO ingestion attenuated 3-methylhistidine excretion 48 h following the exercise bout. CHO + EAA resulted in a 26% decrease (P<0.01), while PLA displayed a 52% increase (P<0.01). fCSA increased across groups for type I, IIa, and IIb fibres (P<0.05), with CHO + EAA displaying the greatest gains in fCSA relative to PLA (P<0.05). These data indicate that CHO + EAA ingestion enhances muscle anabolism following resistance training to a greater extent than either CHO or EAA consumed independently. The synergistic effect of CHO + EAA ingestion maximises the anabolic response presumably by attenuating the post-exercise rise in protein degradation.
authors.affiliation: School of Human Movement Studies, Charles Sturt University, Allen House 2.13, Bathurst, NSW, Australia. sbird@csu.edu.au
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Bird
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Tarpenning
authors.forename: Frank E
authors.initials: FE
authors.lastname: Marino
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D000328:Adult; D000601:Amino Acids, Essential / Q000008:administration & dosage / Q000494:pharmacology*; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition / Q000502:physiology; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000494:pharmacology*; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006728:Hormones / Q000097:blood*; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007328:Insulin / Q000097:blood; D008297:Male; D008762:Methylhistidines / Q000652:urine; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D000601:Amino Acids, Essential; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D006728:Hormones; D007328:Insulin; D008762:Methylhistidines; D006854:Hydrocortisone