Ladies may swoon over Ashton Kutcher's muscular physique, but the actor insists he doesn't get fit to impress his fans ? even his No. 1 fan, wife Demi Moore. Rather, he tells the February issue of Men's Fitness magazine, he regularly practices Bikram yoga and Krav Maga, an Israeli combat technique, to prepare for the end of the world. "I'm going to be ready to take myself and my family to a safe place where they don't have to worry," he says. "I stay fit for no other reason than to save the people I care about." Though the comedy star doesn't seem too serious of a guy, he passionately believes civilization is on the brink of a breakdown. "It won't take much for people to hit the panic button," he continues. "You start taking out electricity and satellites, and people are going to lose their noodle!" To find out how Ashton gets ready for mass chaos - and to check out photos of the brown-eyed hunk - pick up an issue of the new Men's Fitness.