Realistic =/= verisimilitude. As long as it doesn't break the verisimilitude of "This is a normal person who has become exceptionally strong, resilient, and skilled, but is still a non-supernatural being" then you can get away with plenty of action-movie or comic-book-isms. E.g., Batman shouldn't have functional knees, working hands, any intact ligaments in his arms, or a single uncompressed spinal disk anymore, but nobody much blinks at Batman being "not superpowered."