Dean Karnazes "Ultramarathon Man"

For a lot of us, running a mile or two is enough to cause some serious pain. Running a marathon is unthinkable. But Dean Karnazes runs ultramarathons. He recently ran 262 miles nonstop -- the equivalent of 10 marathons, like running from Dallas to Houston. Now Karnazes tells why he does it, in his book Ultramarathon Man -- which he didn't even stop running, to write.