(CNN) -- To convincingly yell "I am Hercules!" in his new action movie, Dwayne "The Rock" Johnson had to do more than warm up his vocal chords.
As a former pro wrestler, The Rock was already approaching Greek demigod territory in terms of build, but even he had to change his diet and exercise to become mythologically ripped.
According to USA Today, the 42-year-old actor had to endure a "Hercules diet" that consisted of seven meals a day, extremely heavy on protein.
The Rock would start with a hearty breakfast of four egg whites, five ounces of oatmeal and a 10-ounce filet of steak. By meal No. 3, he'd have wolfed down another eight ounces of chicken breast; eight ounces of halibut; two cups of white rice and two cups of a green vegetable, like broccoli or asparagus.
Meals four through six were essentially more of the same, with a few baked potatoes thrown in instead of rice.
It sounds like a lot -- and that would be because it is -- but The Rock told USA Today the diet was pretty painless.
"The only tough one was the last meal of the day, No. 7," he said, referring to the nightcap of 10 egg whites scrambled with vegetables, plus 30 grams casein protein. "I get back to the hotel room, I'm ready to go to sleep. But I have to down 10 egg whites."
But it sounds like eating those eggs was like downing cake compared to the workout portion of his Hercules training plan.
"It was grueling," The Rock told CNN of his training plan at the "Hercules" premiere in Los Angeles on Wednesday.
"It was for six months, and then it was for an additional six months once I got (on set)," the actor said. "So it was the most challenging role that I had ever taken on -- physically and mentally, but I'm happy to be here and I'm happy to know the movie's good."
The Rock's not just hyping his project. According to RottenTomatoes.com, "Hercules" was 70% fresh as of July 24. Directed by Brett Ratner, the movie follows Hercules into war as he tries to protect the King of Thrace.
Also starring John Hurt and Ian McShane, "Hercules" opens Friday.
CNN's Topher Gauk-Roger contributed to this report.