Magnesium: In some biochemical events and during energy metabolism, magnesium becomes a crucial substance needed for the activity of several enzymes. Some association with magnesium levels and physical performance has been suggested. Some under diet restrictions to maintain or even reduce body weight, possibly causing insufficient magnesium intake, have reported decreases in physical performance. In a clinical trial, subjects taking magnesium supplementation saw increases in their free testosterone levels. Exercise is commonly accepted to increase testosterone levels. With supplementation of magnesium and exercise, subjects saw an increase in their free testosterone levels from before supplementation of magnesium.
Testosterone is significantly correlated with aggression and competitive behaviour and is directly facilitated by the latter. There are two theories on the role of testosterone in aggression and competition.  The first one is the challenge hypothesis which states that testosterone would increase during puberty thus facilitating reproductive and competitive behaviour which would include aggression.  Thus it is the challenge of competition among males of the species that facilitates aggression and violence.  Studies conducted have found direct correlation between testosterone and dominance especially among the most violent criminals in prison who had the highest testosterone levels.  The same research also found fathers (those outside competitive environments) had the lowest testosterone levels compared to other males.