check this out .Here are prove that female genitals are very delicate and sensitive probably not as much as the balls, but much more than any other body part .This is the reason why kick to the stomach is 8x times safer and less painful than kick to the crotch:

http://rapidshare.com/files/32397451/pilka.flv.html

http://rapidshare.com/files/32398190/somegirls.wmv.html