Speaking about his preparation for the role, Johnson recalls it was helpful to learn from Jeff Glasbrenner, the first American amputee to summit Qomolangma, the world's highest peak. 

"I would say the biggest challenge was making sure that I did right by people who are amputees, because, to my knowledge, this is the very first time in the history of Hollywood that a movie of this size portrays the central character as an amputee," explains Johnson, who's also credited as a producer on the movie.

"I was able to spend a lot of time with Jeff. He has really done extraordinary things as a human being … I was able to walk away from this movie with a higher respect for and consciousness about amputees," he says, adding the acting experience has normalized his view about disabilities.

During the filming, Johnson wore a special mechanism to help him move like he only had one leg. It was wrapped in a green sock, to allow the special effects team to replace it with an artificial limb in postproduction.

"I want to make sure that I performed all the movements correctly and put in a respectful performance," says the 46-year-old star.

Aside from the physical challenge, Johnson, a father of three children, also feels personally connected to the role. In the movie, Sawyer marries the doctor who treats him following his amputation－played by actress Neve Campbell－and has two children.