When the hotel phone rang at 5 a.m. Sunday, Lauren Fleshman was already awake. Along with about 25,000 others in the New York field, she was running her first marathon. And she had the same hope, curiosity, excitement and anxiety as anyone else who had never run 26.2 miles.

Am I ready? Am I strong enough? Where are the portable toilets?

“I’m not afraid of hitting the wall,” Fleshman, 30, of Eugene, Ore., had said a few days earlier. “It would be an honor to hit the wall. I just don’t know what to do if I have to go to the bathroom.”

Unlike most first-timers, Fleshman is a professional, not an amateur. Sunday for her was a rare experiment. She is a track runner. In late summer, she finished seventh at 5,000 meters at the world championships. No American woman had ever finished higher in the event.

But to have any chance for a medal at the 2012 London Olympics, Fleshman realized she needed more power and endurance to defeat the Kenyans and the Ethiopians. Perhaps marathon training would give her added strength on the track.