Swimming almost four kilometers, cycling 180 kilometers, and then running a marathon – that's par for the course for long-distance triathletes. What's unimaginable for most people is completely normal for Sebastian Kienle.
35-year old Sebastian Kienle is a professional triathlete -- and one of the world's best. But his life is not all gold medals and glory. Many of the competitions he enters are so challenging that he can only take part in a few each year. Even getting a slight cold can mean his body can't withstand the exertion. Just ahead of competitions he even debates whether to go to the grocery store for fear of catching something. What makes such extreme athletes push their bodies to the limit?