A research published by the US National Library of Medicine and the National Institutes of Health found that after 7 days of not ejaculating, men's testosterone levels reached 145.7% of the baseline.

The interesting thing is that they didn't observe significant fluctuations from the baseline on days 2 through 5. The research also showed that the peak levels were at day 7. This means that, the next time you have a big football game and you want to be as manly as possible, you might wanna try to take cold showers every day the week before it!