Recently I read a book on Xi Sui Jing. The book is by Yang Jing-Mwing and is called something like 'Qigong the secret of youth'. It covers a section on a set of techniques called Xi Sui Jing.
It is amazing how well the Chinese knew stuff. It comes down to a technique to stimulate testosterone production through various means.
I recommend reading up on this stuff, it's a viable alternative to the herbal/ pharmacological approach!