It was on his way through the tunnel into the Bird’s Nest stadium when Ryan Hall had his epiphany.

His disappearing dream of Olympic triumph was about to end in a disappointing tenth place, when he says that God spoke to him. “He told me I had everything I needed,” he recalled.

There is light at the end of the tunnel for American distance running, too. Hall is in the vanguard of the change, providing a patriotic Prozac pill for the fans watching the ING New York City Marathon on Sunday, but if he is a gifted runner, he is a more remarkable man. So much so that he is planning to give away his $130,000 (about £80,000) pay cheque should he win.

“If I could change someone’s life or have a medal round my neck, then I’d change someone’s life,” he said before talking about how Eric Liddell, the Scotsman who refused to run on the Sabbath at the 1924 Olympics, is his touchstone. “Whether you’re Christian or non-Christian, you can be inspired by someone running for something different to just sport,” Hall said.

“That’s what I’d like to bring to sport. I’d like to challenge people to run with a different mentality. That’s what Eric Liddell challenged me to do. I want to change the way people look at sport. I’ve thought about how Jesus would run the New York Marathon and decided it would look totally different from the usual egotistical athlete.”

Hall reconciles his faith and career by simply wanting to do his best. He is only five races into his marathon career, but already he has a best time of 2hr 6min 17sec, making him the fastest American-born marathon runner and one of only five non- Africans in the all-time top 25.

He has achieved much and experienced more, from the tragic death of his friend, Ryan Shay, at the United States Olympic trials, to his epiphany in China, the country where Liddell was born and later lived as a missionary. If the trappings of modern sport often render it a distasteful bling and buy sale, Hall sees the bigger picture.

“I’m only 27 but I think about the legacy of my running,” he said. “I can run fast times, but people will come along and run faster. So how can you make a difference, something that trickles down from generation to generation?”

One way is the Hall Steps Foundation, which he set up last month to combat poverty and give inner-city children a chance to run. “We also want to sponsor lawyers to fight against human trafficking,” he said. The first step has been to adopt a school in each of New York’s five boroughs.

This is broad-brush altruism from Big Bear, California, but the intriguing thing is the generosity does not deflect from the necessary selfishness of the sportsman. Hall was third in the Boston Marathon in April and has ambitious goals. “It was hard at the Olympics,” he said. “I came back prematurely after the London Marathon. This time I feel I’m ready to take a swing at winning [in New York].” He would be the first American man to do so since Alberto Salazar in 1982, but plans to donate his prize money to better causes. He also has a long-term vision.

“The thought of winning gold in 2012 is what excited me most about my training,” he said. “If I’m not ready then, I don’t think I ever will be.”

With Dathan Ritzenhein finishing third at the World Half Marathon Championships, the USA is emerging from the wilderness. “I don’t think it’s a coincidence that there’s a bunch of us,” Hall said. “It shows the power of believing. One guy runs a four-minute mile for the first time and suddenly there are a bunch of guys doing it.”

The other motivator is a good reason. “In Africa they are often running for their communities or their families, and the great thing about London is everyone runs for charity. You run so much better when you run for someone else.”

Hall grew up wanting to be a baseball player, but did not have the physique. His prospects of becoming a runner were slimmer still, given that his school had no track team and the winters meant he would train in snowdrifts. Climbing mountains informs his view that Haile Gebrselassie’s world record of 2hr 3min 59sec is a temporary wonder. “I believe someone will run the marathon in under two hours in my lifetime,” he said.

Hall will be content if he just gets the best out of a God-given talent. “Only one guy can win but not everyone else fails,” he said. “The marathon is special because 40,000 people are all connected. We all cover the same ground. That’s when athletics can be a beautiful thing.”