The paper is
Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training
The purpose of this study was to investigate associations between acute exercise-induced hormone responses and adaptations to high intensity resistance training in a large cohort (n = 56) of young men. Acute post-exercise serum growth hormone (GH), free testosterone (fT), insulin-like growth factor (IGF-1) and cortisol responses were determined following an acute intense leg resistance exercise routine at the midpoint of a 12-week resistance exercise training study. Acute hormonal responses were correlated with gains in lean body mass (LBM), muscle fibre cross-sectional area (CSA) and leg press strength. There were no significant correlations between the exercise-induced elevations (area under the curve—AUC) of GH, fT and IGF-1 and gains in LBM or leg press strength. Significant correlations were found for cortisol, usually assumed to be a hormone indicative of catabolic drive, AUC with change in LBM (r = 0.29, P < 0.05) and type II fibre CSA (r = 0.35, P < 0.01) as well as GH AUC and gain in fibre area (type I: r = 0.36, P = 0.006; type II: r = 0.28, P = 0.04, but not lean mass). No correlations with strength were observed. We report that the acute exercise-induced systemic hormonal responses of cortisol and GH are weakly correlated with resistance training-induced changes in fibre CSA and LBM (cortisol only), but not with changes in strength.
Whatever causes increased strength and muscle growth, it seems that it is not down to changes in the hormones relating from resistance training.
In the first study, researchers examined the responses of both male and female participants to intense leg exercise. Despite a 45-fold difference in testosterone increase, men and women were able to make new muscle protein at exactly the same rate.
"Since new muscle proteins eventually add up to muscle growth, this is an important finding," says West.
"While testosterone is definitely anabolic and promotes muscle growth in men and women at high doses, such as those used during steroid abuse, our findings show that naturally occurring levels of testosterone do not influence the rate of muscle protein synthesis."
In the second study, researchers analyzed the post-exercise hormonal responses of 56 young men, aged 18 to 30, who trained five days a week for 12 weeks in total.
The men experienced gains in muscle mass that ranged from virtually nothing to more than 12 pounds, yet their levels of testosterone and growth hormone after exercise showed no relationship to muscle growth or strength gain.
Surprisingly, the researchers noted that cortisol—considered to have the opposite effect of anabolic hormones because it reduces protein synthesis and breaks down tissue—was related to the gain in muscle mass.
"The idea that you can or should base entire exercise training programs on trying to manipulate testosterone or growth hormone levels is false," says Stuart Phillips, a professor in the Department of Kinesiology. "There is simply no evidence to support this concept." from Eureka
Now there is some fascinating stuff there.
- Natural levels of testosterone - don't have an impact. Steroids will blow you up OK, but you can't blame you age (lowered testosterone levels) or your sex.
- Natural levels - i.e. promoted by exercise - of GH and testosterone - were not related to either muscle growth or strength.
- Cortisol - the scary stress hormone that we are supposed to minimise due to its catabolic effects - was associated with hypertrophy.
As Philips says, theories that it is all down to the usual hormones - testosterone and GH - may be wrong but stress from training - cortisol promoting - may have a role. Training to produce stress...failure? HIT perhaps?