Rumney, who raced stock cars in Rotorua over the summer, said his competitive nature helped him nail Halberg's winning persona.
"I really enjoyed the chance to get out there and run, they would get in extras from running clubs around Auckland and I would have to win.
"We still had to make it look realistic so I'd be pretty knackered by the end of the day."
He said to get the role he had turned up to auditions in some stubbies and a running singlet to impress the judges.
"After auditioning they said I was skinny enough to have the part."
He said acting in his first film was a real buzz and during the two weeks of filming, earlier this year, he and the other actors were treated like kings.
Rumney said the film was made up of interviews with the real runners Murray Halberg, Peter Snell and coach Arthur Lydiard and dramatisation from the cast, who acted out their experiences.
After growing up in Rotorua and attending Western Heights High School, Rumney decided to study performing arts at Unitec in Auckland, where he graduated in 2010.
His mother Robyn-Ann Rumney, who worked at Rotorua Little Theatre, said she was very proud of her son. "It's fantastic, we can't wait to see him in the movie, his father and I are very proud of him."
She said he had come a long way since acting as Aladdin in his first school play.
Rumney hopes to continue building his career doing more New Zealand films, children's theatre and advertisements.
He lives in Palmerston North and looks forward to seeing the feature film for the first time on Sunday.
