PW met Dean Karnazes, author of Ultramarathon Man, on a recent cold, rainy morning in New York's Central Park. After completing 262 miles nonstop (that's 10 marathons in a row) in October, Karnazes has now dropped his weekly mileage to a paltry 70 or so. As we ran the 10K loop of thepark with him—at a very conversational, nine-minute-mile pace—he told us about running a 135-mile trek in Death Valley (his sneakers melted on the asphalt; bread toasted in the air); running a marathon to the South Pole; and other tales of avery long-distance runner.

PW: There doesn't seem to be an easy answer to the question of why you run such distances, and why you run in such extreme conditions, but your book explains a lot.

Dean Karnazes: Yes, it does. The death of my sister [Pary, on the eve of her 18th birthday, when Karnazes was in college] was devastating to me. That inspired me just to live every day as best I could. And I love it. The truth is that it's what I feel passionate about. People say, "How long are you going to keep this up?" And I say, "As long as the passion's still there. If there's a fire in my heart to do it, I'm going to keep doing it. If it goes away, then I'll stop."

In your book, you talk about experiencing pain while running, and the idea that suffering is "the sole origin of consciousness."

In Western society, we've tried to figure out every comfort possible, and we thought that if we were comfortable and had every convenience available, then we'd be happy. I just don't believe it anymore. I think that you feel much more alive when you're struggling. And life in a lot of ways really is a struggle, and we just kind of mask that origin with buildings and things like that.

When you were running the 262 miles, you must've been struggling at some point.

[Laughs.] Many points, yes.

But did you ever reach a point when you said to yourself, "I can't do this. I can't go on"?

Yes. That crossed my mind a lot of times. What I do in those circumstances is just set little micro-goals: the goal of getting to the next stop sign, and getting to the traffic light, and getting through those lows. That's one thing I really like about the long, long distances. It's like a mini-drama, because you have these lows, and the world is horrible. When you can't make it and you feel like you can't take another step, it's depressing, it's more depressing than you could ever imagine. To me it's devastating. To feel that low, and then, 10 miles later, to feel like, "God, the world is filled with possibilities, I feel wonderful"—to be on that runner's high, to me it's just a roller coaster. It's almost of like a drug, I guess, but I really enjoy that.

What do you think about the group of Buddhist monks who run 52.5 miles every day for 100 consecutive days?

I think it shows you what the human body is capable of, but I think it's pretty darn extreme.

Your book is about your experiences running, but it's also a larger story about human endurance overcoming insurmountable odds. Did you have an audience in mind?

No. When I wrote the book, I thought, just tell your stories, tell it like it is, try and tell them how you feel when you do these things, why you do it as best as you can, tell them some of the funny things that happen. Be truthful, and if it appeals to people, it does, if it doesn't, it doesn't. I'm not a trained writer, so I figured if I tried to write anything besides what I do, I'd screw it up somehow.