Why run a marathon? Pro-athletes and psychologists explain

Every year, there's a new story about someone crawling, being lifted, or not even making it to the finish line of a marathon.

And every year, as spectators watch in awe as thousands of athletes run a grueling, painful 26.2 miles in the TCS New York City Marathon, they may be asking themselves: Why do people choose to do this?

ABC News went to the professionals to ask why they put their bodies through this --if not for the grand prize and title at the end. Read Here