What drives an extreme athlete? Find out from Ellyn Brown, a 54-year-old Alaskan who is the U.S. mountain running champ and one of the best snow shoe racers alive.

We all know the little old lady that lived in a shoe, but Georgia Kleinhenz is known as the Legendary Little Old Lady on a Bike. She got her name because of how many six-day bicycle tours she's done. Can you say 28?

Many try -- not all succeed. But it seems that these days, the biggest names in mountain climbing are people over the age of 50! In fact, a group of 70-year-olds is hoping to smash the record for climbing Mount Everest.