I'm not going to rip the whole page, so check the link for more information..
The rats stayed in the bath for 10 minutes each time. After 4 weeks the researchers measured the animals’ testosterone and LH synthesis.
The hot baths had no effect on the young lab rats, but in the old rats their testosterone level went down by a factor of 3.Exposing the testes to high temperatures reduces the effect of the enzyme P450c17 and the StAR protein – full name steroid acute regulatory protein. StAR is a key protein in the conversion of cholesterol into testosterone in the testes. The old rats that had hot baths produced none at all.
The Koreans think that their findings apply to humans too. "Hot baths may have negative effects on testosterone synthesis in older human males”, they write in the last paragraph of their article.
So, cold showers for 30 minutes at around 41-43 degrees Celsius was able to raise testosterone levels. I guess, through the coldness of the scrotum.. Why not, stimulate the coldness of the scrotum by applying a ice pack on?
I wonder though, what is the limit to this? What if I have a ice pack strapped on my balls for 60 minutes?