“In general, all types of exercise stimulate the release and production of testosterone,” says sports medicine doctor Jordan Metzl, ., author of The Exercise Cure . “But there is data to suggest that lifting weights and high-intensity work might stimulate the greatest release of testosterone.” While research shows that those post-workout super-spikes may be temporary, the overall boosting benefit of regular exercise can’t be ignored. Pretty much any and all resistance work is worthy of a place in your T-tweaking program; on the other hand, long, slow cardio slogs, such as everlasting jogging sessions, may have a negative effect on testosterone levels.
The second theory is similar and is known as "evolutionary neuroandrogenic (ENA) theory of male aggression".   Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible.  The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.  Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.     
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