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.     
As a result, Trenbolone Acetate now functions as the primary anabolic compound (aka the ‘workhorse’ compound) that will function to provide the muscle growth throughout the cycle. Trenbolone is strictly an advanced level anabolic steroid, unfit for use by beginners of any type. In this cycle, the Acetate variant of Trenbolone is utilized simply due to its seamless compatibility with Testosterone Propionate. This is because the Propionate and Acetate esters as, previously mentioned early on in this section of the profile, both possess almost identical half-lives (3 days for Trenbolone Acetate and days for Testosterone Propionate). This therefore provides an ease of convenience for the user, as well as smoother injection and administration frequencies. The fact that Testosterone is being utilized at a low enough doses to avoid aromatization, combined with the fact that Trenbolone’s inability to convert into Estrogen at any dose should result in the total elimination of any potential water retention, bloating, gynecomastia or any side effects associated with Estrogen . It is important to note that this cycle in particular is strong enough to be utilized as a bulking cycle, lean mass cycle, or cutting cycle – all without the inflated potential for water retention or other Estrogenic side effects .
The partition coefficient of the ester in question is important because is effects how long the drug itself stays in the system. If the testosterone transfers too quickly from the oil to the blood, the result is a sudden spike in testosterone which then rapidly drops once the dose has been used up. In the example of free testosterone injected into the muscle from a water suspension (as in Aquiviron, mentioned above), the testosterone is essentially immediately available to the bloodstream due to its low partition coefficient, and thus there is an immediate spike of testosterone which is used up quickly in the body.