Matt Damon's action-packed role in the sci-fi film Elysium required him to not only buff up his already fit physique but also shave his head, which was probably the most drastic element of his role transformation. Damon explains how his family received the makeover.
"They liked it," Damon revealed to ET's special correspondent Vivica Fox. "Actually, my baby, at the time, was less than a year old and she would just play the drums on my head. When your kid's that age, you'll do anything...that puts a smile on their face, so I would just lay my head on her lap and she'd just [drum on it]."
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Although the 42-year-old actor typically maintains good fitness, he had to beef up for his role as the film's protagonist, "Max DeCosta," who is challenged with the overwhelming task of saving the fate of humanity.
He confirmed that he was exercising around four hours per day to put on muscle for the film.
"If I was 25, it would have been an hour a day," Damon said. "It was two hours of weightlifting in the morning. ... There was bodybuilding and then there was cardio in the afternoon. It was a lot."
VIDEO: Matt Damon's Attack on 'Elysium'
While the film's action remains at the forefront of Elysium, interwoven throughout the film are sociological and political issues, such as health care and immigration.
"First and foremost, we wanted to make a big summer movie, a big action, fun, entertaining movie, but I love that about the movie—that it's about something more than that," said Damon.
Watch the full video above for more from Damon, including his recent move back to Los Angeles and his vow renewal, and his co-star, Sharlto Copley as well.
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Elysium is in theaters this Friday (August 9).