French, D. N., Volek, J. S., Ratamess, N. A., Mazzetti, S. A., Rubin, M. R., Gomes, A. L., Wickham, R. B., Doan, B. K., McGuigan, M. R., Scheet, T. P., Newton, R. U., Dorofeyeva, E., & Kraemer, W. J. (2001). The effects of creatine supplementation on resting serum hormonal concentrations during short-term resistance training overreaching. Medicine and Science in Sports and Exercise, 33(5), Supplement abstract 1142.

Resistance trained males (N = 17) were randomly assigned to a creatine supplementation (0.3 g/kg/day for week 1; 0.5 g/kg/day for weeks 2-4) or a placebo group. Resistance training was in two, two-week phases. The high phase used three sets of 8-12 repetitions of eight exercises and the low phase used five sets of 3-5 repetitions of five exercises. Exercises stressed the major muscle groups. Training occurred on four consecutive days each week. Blood samples were drawn before the experience and at the end of each week.

Total testosterone decreased in both groups by the end of week 3. Free testosterone did not decrease in the creatine group but decreased significantly at the end of week 2 in the placebo group. Sex hormone-binding globulin did not change in the creatine group but increased significantly in the placebo group. Growth hormone did not change in either group. Hemoglobin decreased in placebo but not in the creatine group. Plasma creatine increased significantly in the creatine group but did not change in the placebo group. Uric acid increased in placebo and decreased in the creatine group.

The creatine group maintained the Total testosterone to sex hormone-binding globulin ratio and prevented an increase in uric acid, changes that could partially contribute to increased resistance training performance.

Implications. Creatine supplementation is associated with hormonal changes at rest in resistance trained individuals.

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