The latest 30 for 30 documentary “The Infinite Race” explores the story of the Tarahumara. The indigenous runners in Mexico are famous for running incredible distances on mountain trails, often barefoot or in sandals. Director Bernardo Ruiz takes us behind the making of the film, which grapples with the impact of modern, Western ultrarunners taking interest in the Tarahumara, and the pressures on their villages from drug cartels and violence.