Came across some interesting research making a very strong case arguing that the post exercise elevations in GH and testosterone do NOT increase muscle growth but rather aid in fuel mobilization (1). Instead, muscular adaptations are a result of more localized anabolic signals caused by the mechanical tension from exercise.

Here are a few key points from this paper:

- Despite females having 10x lower testosterone levels compared to men, a study done by Hubal et al., 2005 (342 women, 243 men aged 18-40) found that after 12 weeks of resistance training there was not a significant difference in relative muscle growth between men and women. Additionally, this study found a weak correlation between age and muscle growth and as we know, anabolic hormone levels drop with age (2).

- It has been shown that without exercise, administration of testosterone can muscle growth (3). A study done by West et al., 2009 performed a resistance training study with varying hormone elevations. One group performed a bicep curl workout, which did not lead to a significant increase in anabolic hormones. A second group did the same thing but immediately followed up with a leg workout intended to increase anabolic hormones. Even with elevated hormones in the second group there were no significant differences in biceps protein synthesis between groups (4)

As pointed out in the main paper I am referencing (1), it seems to be the case that in suppressed states of anabolic hormones there is a negative impact on muscle growth. On the other end, supra-physiological levels of anabolic hormones (through exogenous administration) have a positive impact on muscle growth. However, under normal conditions, these hormones do not have a significant effect on muscle growth.



(1) http://www.ncbi.nlm.nih.gov/pubmed/20959702

(2) http://www.ncbi.nlm.nih.gov/pubmed/?...tance+Training

(3) http://www.ncbi.nlm.nih.gov/pubmed/8637535

(4) http://www.ncbi.nlm.nih.gov/pubmed/19736298