Effects of liquid carbohydrate/essential amino acid ingestion on acute hormonal response during a single bout of resistance exercise in untrained men.
OBJECTIVE
The primary objective of this study was to investigate the influence of nutritive interventions on acute hormonal responses to a single bout of resistance exercise in untrained young men. Specifically, the aim was to determine whether the acute hormonal milieu conducive to enhancing skeletal muscle hypertrophic adaptation to resistance training could be created. The potential role of cortisol in inhibiting training-induced muscle growth is of particular interest, as is whether exercise-induced cortisol release can be attenuated by nutritive interventions.


METHODS
After a 4-h fast, 32 subjects performed a single bout of resistance exercise ( approximately 60 min), during which they consumed a 6% carbohydrate (CHO) solution, a 6-g essential amino acid (EAA) mixture, a combined CHO+EAA supplement, or a placebo beverage. Blood samples were collected every 15 min throughout the exercise bout, immediately after exercise, and 15 and 30 min after exercise for analysis of total testosterone, cortisol, growth hormone, insulin, and glucose.


RESULTS
No significant change in glucose or insulin was observed for placebo. CHO and CHO+EAA ingestion resulted in significantly (P < 0.001) increased glucose and insulin concentrations above baseline, whereas EAA resulted in significant postexercise increases (P < 0.05) in insulin only. Placebo exhibited a significant increase in cortisol within 30 min (P < 0.01), with a peak increase of 105% (P < 0.001) immediately after exercise, and cortisol remained 54% above baseline at 30 min after exercise (P < 0.05). Conversely, the treatment groups displayed no significant change in cortisol during the exercise bout, with CHO and CHO+EAA finishing 27% (P < 0.01) and 23% (P < 0.05), respectively, below baseline at 30 min after exercise. No between-group differences in exercise-induced growth hormone or testosterone concentrations after nutritive intervention were present.


CONCLUSIONS
These data indicate that CHO and/or EAA ingestion during a single bout of resistance exercise suppresses the exercise-induced cortisol response, in addition to stimulating insulin release. We conclude that the exercise-induced hormonal profile can be influenced by nutritive interventions toward a profile more favorable for anabolism.
Bird
Stephen P
SP
School of Human Movement Studies, Charles Sturt University, Bathurst, New South Wales, Australia. sbirg@csu.edu.au
Tarpenning
Kyle M
KM
Marino
Frank E
FE
D000293:Adolescent; D000328:Adult; D000601:Amino Acids, Essential / Q000494:pharmacology*; D019540:Area Under Curve; D001786:Blood Glucose / Q000032:analysis; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004311:Double-Blind Method; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood* / Q000378:metabolism; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D000078790:Insulin Secretion; D008297:Male; D013739:Testosterone / Q000097:blood; D014891:Weight Lifting / Q000502:physiology*
D000601:Amino Acids, Essential; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin; D019382:Human Growth Hormone; D013739:Testosterone; D006854:Hydrocortisone