ENDOGENOUS GROWTH HORMONE, INSULIN-LIKE GROWTH FACTOR, AND FREE TESTOSTERONE DO NOT HAVE ANABOLIC CAPACITIES NOR ARE THEY ASSOCIATED WITH STRENGTH GAINS
West, D. W., Hartman, J. W., & Phillips, S. M. (2011). Retrospective analysis of resistance training-induced strength and hypertrophy: separating the wheat from the hormone chaff. Medicine and Science in Sports and Exercise, 43(5). Supplement abstract 663.
This study investigated associations between purportedly anabolic acute exercise induced hormone responses and adaptations to resistance training in a cohort with normally distributed training-induced adaptations. Acute post-exercise serum growth hormone, free testosterone, cortisol, and insulin-like growth factor (IGF-1) responses were determined at the midpoint of a 12-week resistance exercise program conducted previously. Correlations of hormonal responses with gains in lean body mass, muscle fiber cross-sectional area, and leg press strength were investigated. Dietary factors were combined with hormonal responses as independent variables in multiple regression analysis of adaptations to resistance training.
There were no significant correlations between the exercise-induced elevation of serum growth hormone, free testosterone, and insulin-like growth factor and gains in lean body mass or leg press strength. Significant, but low correlations were found for cortisol with change in lean body mass and Type II fiber cross-sectional area as well as growth hormone and gains in Type I and Type II fiber area. Increments in daily dietary protein intake and the daily consumption of dairy, but no acute hormonal response, were significant predictors in a model of change in lean body mass and Type II fiber area.
Implication. There is a significant association between growth hormone and cortisol and fiber hypertrophy, but there is no association between any hormones and strength gains. There is an important role of increasing dietary protein and servings of dairy in promoting training-induced gains in lean body mass and fiber hypertrophy. Post-exercise elevations in endogenous hormones are relatively impotent in their predictive value for resistance training-induced hypertrophy. Endogenous hormones appear to have little anabolic capacity. Why exogenous forms of the same substance would have an anabolic effect (as claimed by WADA) is baffling.
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