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RESEARCH PRODUCT

Protein Ingestion Prior to Strength Exercise Affects Blood Hormones and Metabolism

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HULMI, J. J., J. S. VOLEK, H. SELANNE, and A. A. MERO. Protein Ingestion Prior to Strength Exercise Affects Blood Hormones and Metabolism. Med. Sci. Sports Exerc., Vol. 37, No. 11, pp. 1990 -1997, 2005. Purpose: The effects of protein consumption before strength training session on blood hormones, energy metabolites, RER, and excess postexercise oxygen consumption (EPOC) were examined. Methods: Ten resistance-trained young men consumed either a 25 g of whey and caseinate proteins (PROT) or a noncaloric placebo (P) in a liquid form 30 min before a heavy strength training session (STS) in a crossover design separated by at least 7 d. STS lasted 50 min and included 5 1 RM squats, 3 10 RM squats and 4 10 RM leg presses with 2-, 3-, and 2-min recoveries, respectively. A protein-carbohydrate supplement was consumed after STS in both trials. Venous blood samples were collected before, during, and after STS and oxygen consumption before and after STS. Results: Serum growth hormone (GH), testosterone, and free fatty acids (FFA) were significantly (P 0.05) higher in P compared with PROT 5 min after an STS. The calculated area under curve (AUC) of the serum insulin response during an STS was significantly (P 0.001) higher in PROT compared with P. The EPOC value from 90 to 120 min after an STS was significantly greater in the PROT condition compared with P (P 0.01), and PROT treatment had a significantly higher RER 2 h postexercise (P 0.04). The AUC of serum FFA during STS correlated significantly and negatively with RER 10 -30 min after STS (r 0.53, P 0.02). Conclusions: Consuming 25 g of whey and caseinate proteins 30 min before an STS significantly decreases serum GH, testosterone, and FFA levels, and increases serum insulin during an STS. Furthermore, the pre-STS protein increased EPOC and RER significantly during 2-h recovery after STS. Key Words: EXERCISE, INSULIN, GROWTH HORMONE, TESTOSTERONE, FREE FATTY ACIDS, EXCESS POSTEXERCISE OXYGEN CONSUMPTION