Carol O'Hear, who has run 25 ultramarathons, placed third in her division at last year's Antarctica Marathon.
O'Hear has some advice for Jill Homer, who's training to bike 350 miles in the human-powered Iditarod this February. O'Hear says she underestimated how much water she'd need to drink. The marathoner recommends ways to remind yourself to keep drinking, and ways to keep your water from freezing.
If Homer should fail on either count, O'Hear says, debilitating cramps await. "You don't feel like you're sweating that much because it's so cold out, but because of the dry air, it's really sucking the moisture out of your body," she says.