UC Irvine

The effect of a single exercise as well as exercise training on the growth hormone (GH)-insulin-like growth factor (IGF-I) axis and inflammatory cytokines was studied mainly in adults participating in individualized endurance-type sports. The gender-specific effect of exercise on these systems in adolescents is unknown. Therefore, the purpose of this study was to evaluate the effect of a typical volleyball practice on anabolic (GH, IGF-I, and testosterone) and catabolic hormones (cortisol) and inflammatory mediators (interleukin-6 [IL-6]) in elite, national team level, male (n = 14) and female (n = 13) adolescent volleyball players (13-18 years, Tanner stage 4-5). Exercise consisted of a typical 1-hour volleyball practice. Blood samples were collected before and immediately after the practice. Exercise led to significant increases in GH (0.2 +/- 0.1 to 2.7 +/- 0.7 and 1.7 +/- 0.5 to 6.4 +/- 1.4 ng x mL, in men and women, respectively, p < 0.05 for both), testosterone (6.1 +/- 0.9 to 7.3 +/- 1.0 and 2.4 +/- 0.6 to 3.3 +/- 0.7 ng x mL, in men and women, respectively, p < 0.05 for both), and IL-6 (1.1 +/- 0.6 to 3.1 +/- 1.5 and 1.2 +/- 0.5 to 2.5 +/- 1.1 pg x mL, in men and women, respectively, p < 0.002 for both). Exercise had no significant effect on IGF-I, insulin-like growth factor binding protein-3, and cortisol levels. There were no gender differences in the hormonal response to training. Changes in GH and testosterone after the volleyball practice suggest exercise-related anabolic adaptations. The increase in IL-6 may indicate its important role in muscle tissue repair. These changes may serve as an objective quantitative tool to monitor training intensity in unique occasions in team sports.