DES MOINES, Iowa — In researching wrestling for the upcoming film "Foxcatcher," director Bennett Miller kept coming back to a simple question.

Why?

Miller wondered what drove wrestlers to suffer through tremendous hardship, dedicate themselves so completely and compete so intensely despite little promise of tangible rewards. Miller, an Oscar-nominated director perhaps best known for directing "Moneyball," found the answers "deeply moving and highly personal."

The experience quickly turned him into a supporter of a sport now fighting for its Olympic existence.

"The reason why people wrestle felt more pure to me," Miller told The Associated Press in a phone interview on Wednesday. "If you're in that sport, you're not doing it for money and you're not doing it to become famous. I found that an impressively high concentration of people were in it the intrinsic values of it."

Those efforts could lead to one of the most influential movies ever connected to wrestling.

"Foxcatcher," which is set to be released in late 2013, tells the story of John du Pont, the chemical fortune heir who killed Olympic gold medal-winning wrestler Dave Schultz at his estate near Philadelphia in 1996. Schultz, a 1984 gold medal winner, had come to live and train at the state-of-the-art Foxcatcher National Training Center that du Pont had built on his 800-acre property.

After the shooting, du Pont barricaded himself inside his home for two days, but was taken into custody when he left his mansion to fix a boiler police had shut off. Found guilty but mentally ill in the slaying, he died in prison in 2010 at the age of 72.

The movie features Steve Carell as du Pont, Mark Ruffalo as Dave Schultz and Channing Tatum as his brother, Mark Schultz. Miller, the cast and the crew spent years working on the movie, and the experience persuaded Ruffalo to assist the U.S.-based Committee to Preserve Olympic Wrestling.

The IOC recommended in February that wrestling be left out of the Olympics in 2020. But last month it was one of three sports selected to compete for the last provisional spot in the 2020 and 2024 Olympic Games, along with squash and a combined bid from baseball/softball. A final vote is expected by the IOC general assembly during its meeting in Buenos Aires in September.

Ruffalo attended the exhibition between the U.S., Russia and Iran in New York in May and he also shot a public service announcement for CPOW that was released Tuesday.

"It shows that the sport has motivated people to move to keep it in the Olympics and motivated enough people to push the IOC to reconsider," Ruffalo said of the push to save Olympic wrestling.

Ruffalo, who was nominated an Academy Award for his work in "The Kids Are All Right," has long held a personal connection to wrestling. Ruffalo's father, Frank, was a standout wrestler in his youth, and he encouraged his son to compete as well. Ruffalo wrestled from seventh through 11th grade in Wisconsin and Virginia Beach, Va.

"It was profound for me," Ruffalo said. "It was probably the most — as far as training for the world, my career and success — wrestling played a big part in that. The amount of discipline and determination and will and just moxie that you have to have to be a wrestler."

Ruffalo said he put on 30 pounds to play Schultz, who won gold at the Los Angeles Games at 74 kilograms. Ruffalo, Tatum and others worked with several members of USA Wrestling in an effort to accurately portray the sport.

"They really opened up their arms to me once they saw I could really wrestle," Ruffalo said. "They're a very tight-knit group of people that are protective of their sport ... it's just a classy, classy, classy group of people."

Filming also opened the eyes of Miller, who acknowledged that he was neither familiar with nor particularly interested in wrestling until he started work on "Foxcatcher."

One of the first people Miller met through USA Wrestling was Dave Bennett, an eye doctor who gave up his practice to pursue his passion for coaching and working with wrestlers.

"What drew into this movie is a story that, to be honest had nothing to do with wrestling ... I was interested in the characters, the whole story," Miller said. "During the research, I went to various tournaments and got to know wrestlers and about the sport, and it really drew me in. It altered my perceptions, and learning about the sport was like a portal into a new understanding and appreciation for the value system."