Thanks to svehunter for the link above:
Quote from Adrian Brody:
"...but it’s not the physical strength that outsmarts an alien with energy-based weapons and higher tracking skills, and a culture of hunting and trophy-hunting, you have to outsmart them.
I approached this with the kind of level of focus I would approach any of the roles that I’ve been given an opportunity to play… I think my intention, and the intention of hiring me to play Royce, was to delve into the kind of flawed tragic hero and not this kind of typical … overtly physically imposing character… I did put on a substantial amount of muscle mass for the role, and the physical training was a big part of building to that character, [but it was also important] to prepare psychologically. We shot in Hawaii, and we shot in thousands of acres of tropical rainforest, and I had gotten permission from the owners of the estate to stay in the property… I didn’t stay in a hotel… [Instead,] I isolated myself… My nightly ritual was poring over survival manuals and military and paramilitary training books. I was reading Sun Tzu. I was studying meditation. I was on a very strict diet. I wasn’t drinking. I wasn’t eating sugar. I wasn’t having sex. I had to kind of go there, for me, because this was a tremendous opportunity."
Its so exciting to see an actor put this kind of determination into his character!!!