toned arms

Now let's get into it: Here's how Portman got those toned arms.

Pendergast noted that they only had four months before shooting started to get Portman to look like Mighty Thor. She said it was the star's dedication that led to the results they got.

"Natalie is a very focused, hardworking, and determined woman, which was the main reason we were able to reach the goal look in time for filming," Pendergast said.

Here's the workout routine Portman did to get her toned arms:

Warm-up:

30 seconds: Marching arms 
30 seconds: Lat stretch 
30 seconds: Beast crawl 
10 reps: Roll down walk outs 
25 reps: Power band kneeling reverse fly 

Main set:

4 sets/12 reps: Banded pull-ups
4 sets/25 reps: Dumbbell straight arm lateral raise
 (rest 1.5 minutes) 
 
4 sets/20 reps: Straight arm raise (palms up) 
4 sets/1 minute: Reverse plank
(rest 1.5 minutes)

4 sets/10 reps: Seated dumbbell Arnold press
4 sets/20 reps: Kneeling banded tricep press
(rest 1.5 minutes)

4 sets/12 reps: Dumbbell bicep curl 
4 sets/20 reps: Banded kneeling rotation 
(rest 1.5 minutes)

4 sets/12 reps: Dumbbell tricep press 
4 sets/1 minute: Squat jumps 
(rest 1.5 minutes)

Cardio:

3 rounds of 2 minutes: Boxing followed by 1 minute of skipping. 
(rest 1.5 minutes then repeat set)

Cool down:

Stretching and release using a foam roller.