How To: Do Scarlett Johannson's butt workout routine from "Iron Man 2"

Modern bombshell Scarlett Johannson literally worked her butt off to get into shape for the role of Black Widow in "Iron Man 2." While always lean, Johannson whittled down her famous curves, losing about ten pounds (a major difference for a woman that small) and gaining a lot of lean muscle.

Check out this fitness video to learn the exact butt workout she did to tone up for the movie.

Check out Scarlett Johannson's workout routine from the set of her new movie "Iron Man 2" as the Black Widow. This lower body butt fitness program helped her get into the best shape of her life without losing her signature curves.