How can there be a young Arnold in Terminator 5?

Well, in order to restore the young T-800 hi-fi robot in Terminator 1, the film crew specially observed Arnold Schwarzenegger's muscles when he was young, and then found a bodybuilder with similar muscle lines. The young T-800 has always been played by this bodybuilder. However, the face is a technical problem, which is synthesized by computer technology.