At 28, Natalie Crawford was diagnosed with cystic fibrosis. She wasn't supposed to run at all, let alone complete four marathons. But Natalie didn't let medical orthodoxy set her boundaries - and in dong so has changed how the world looks at CF and exercise.
Molly Butterworth nearly didn't become a runner at all. Her first passion was swimming and she took some persuading to run a cross-country event. Now she runs for England, has one eye on the Olympics and is a successful coach.
Addison Hendricks was running 130 miles on a track to break American distance records when he was just 16. These days, the 26-year-old races - and wins - events that stretch to 400 miles and are put on by the legendary Lazarus Lake.