Many believe that sex before a competition can have a negative impact on performance in combat, speed and strength sports in males. Athletes from strength and speed sports showed decreased performance up to two hours after sexual intercourse. The most likely cause of this is lower testosterone levels in men after sex and the resulting reduction in aggressiveness.
For this world, I want the myth to be a reality for males, but in the opposite way. Instead of decreasing effectiveness, intercourse leads to a small but noticeable boost in testosterone, leading to a slightly heightened state of aggressiveness and awareness. This would be useful before going into strength and speed competitions, or warfare. The first thought on how to do this would be to link a higher rate of endorphins to increased rate of testosterone. However, anything that gave pleasure, such as eating, smoking, etc, would cause a person to be in a constant higher state of aggression. This would be bad for the individual's body and for society on a bigger level.
How can I get around this factor without negatively affecting someone over the long term?