http://www.mosnews.com/weird/2009/07/07/strongvagina/

A Russian woman has set a new world record, lifting a 14-kg. glass ball with her vagina muscles. Tatiata Kozhevnikova of Novosibirsk, aged 42, has been exercising her intimate muscles for fifteen years, and has already made her entrance into the Guinness Book of Records as the possessor of the world’s strongest vagina, she proudly told Life.ru.

…

“You insert one of the balls in your vagina, and it has a string attached to it with a little hook at the very end. You fix a second ball onto this hook.”

The Russian recommends vaginal exercises to all women who want to improve their sex life.

“It’s enough to exercise your vagina five minutes a day, ladies, and in just one week you’ll be able to give yourself and your man unforgettable pleasure in bed,” she says.

You can improve your muscles too with kegel exercise balls.

Strengthen your pc muscles with exercise balls.