How to run an ultramarathon ? Puff out your chest, put one foot in front of the other, and don't stop till you cross the finish line.

I love surfing, rock climbing, cycling - all that stuff. But it's just amazing that I can inspire people with my running. It's humbling, really.

A lot of ultramarathoners are soloists. They're single and live lives off the grid.

When I ran across America, for 75 days I ate 10,000 calories a day. I still lost about five pounds.

I eat nothing that's processed or refined - no high-fructose corn syrup, no sugar, no trans-fats. I eat a lot of fish and monounsaturated fats from olives, olive oil and nuts. A lot of organic, fresh fruits and vegetables. No bread. No gluten. No wheat. No rice.

As long as my heart's still in it, I'll keep going. If the passion's there, why stop?... There'll likely be a point of diminishing returns, a point where my strength will begin to wane. Until then, I'll just keep plodding onward, putting one foot in front of the other to the best of my ability. Smiling the entire time.

If someone had said to me before I started doing this that a human being is capable of running 100 miles nonstop, I would have just said: 'No way. I mean, how?' If you just go out there and run 100 miles, it breaks down a lot of barriers in terms of self-imposed limitations.