Featuring world famous natural bodybuilder and former American Gladiator, Mike O'Hearn, Generation Iron 4 explores the inner workings of professional natural bodybuilding in attempt to expose the truth behind the all natural claim of the sport. This next chapter in the flagship film series will also feature Kai Greene and explore the controversial world of professional natural bodybuilding alongside top pros competing for Natural Olympia in a league dedicated to ensuring all competitors are free of performance enhancing drugs. With medicine and technology continuing to change at a rapid pace across sports and entertainment, natural bodybuilding as a whole has been criticized and questioned. Can the league guarantee that these competitors are truly natural?