The 33-year-old star had to plan his bathroom breaks well in advance while filming because designers forgot to make allowances in his robot costume, reported Contactmusic.
"Wearing that suit created traction on my shoulder so it was like someone pushing down on me for 14 hours a day," Hunman said.
The 'Sons of Anarchy' actor portrays the leader of a team of soldiers in the film, who pilot giant mechanical robots in a bid to save the world against an alien invasion.