Endogenous Anabolic Hormonal and Growth Factor Responses to Heavy Resistance Exercise in Males and Females

W. J. Kraemer, S. E. Gordon, S. J. Fleck, L. J. Marchiteii, R. Mello, J. E. Dziados, K. Friedl, E. Harman, C. Maresh and A. C. Fry, Endogenous Anabolic Hormonal and Growth Factor Responses to Heavy Resistance Exercise in Males and Females. mt J Sports Med, Vol 12, No 2, pp 228— 235, 1991. Accepted: June 20, 1990 To examine endogenous anabolic hormonal responses to two different types of heavy resistance exercise protocols (HREPs), eight male and eight female subjects performed two randomly assigned protocols (i. e. P-i and P-2) on separate days. Each protocol consisted of eight identically ordered exercises carefully designed to control for load, rest period length, and total work (J) effects. P-l utilized a 5 RM load, 3-mm rest periods and had lower total work than P-2. P2 utilized a 10 RM load, 1-mm rest periods and had a higher total work than P-i. Whole blood lactate and serum glucose, human growth hormone (hGH), testosterone (T), and somatomedin-C (SM-C] (i. e. insulin-like growth factor 1, IGF-l) were determined pre-exercise, mid-exercise (i. e. after 4 of the 8 exercises), and at 0, 5, 15, 30, and 60 mm post-exercise. Males demonstrated significant (p <0.05) increases above rest in serum T values, and all serum concentrations were greater than corresponding female values. Growth hormone increases in both males and females following the P-2 HREP were significantly greater at all timepoints than corresponding P-i values. Females exhibited significantly higher pre-exercise hGH levels compared to males. The P-i exercise protocol did not result in any hGH increases in females. SM-C demonstrated random significant increases above rest in both males and females in response to both HREPs. These data suggest that the hormonal response patterns to HREPs are variable and in females differ from those in males due to significantly higher pre-exercise and exercise-induced serum T levels in males and higher pre-exercise serum hGH concentrations in females.