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The long-awaited Sin City sequel, Sin City: A Dame to Kill For, heats up theatres nationwide today, and while we don't know exactly what the movie has in store, we can promise you one thing: Jessica Alba looks abs-olutely jaw-dropping amazing in it. Reprising her role as a stripper with a heart of gold, she certainly has one killer bod, but where did she get those oh-so-steamy dance moves?

According to personal trainer and dance instructor Jennifer "JJ Dancer" Johnson, it took hard work (we're talking two to five hours of training a day). Johnson choreographed all of Alba's dance sequences in the flick and even helped her up the film's sensuality. We went one-on-one with the fitness pro to steal some of her secrets.

Shape: Congrats on the amazing gig! First off, how did training Jessica Alba for Sin City 2 come about?

Jennifer "JJ Dancer" Johnson (JJ): Thank you so much! In the film, her character was already a dancer from the first Sin City, but this one is supposed to be about eight years later so she needed to be an insanely amazing dancer. Jessica is the one who totally took charge and hired me. She is so hands-on and that's what is so special about her. Not only did she want to be able to freestyle more, but also she wanted to be stronger with the multiple routines she was required to do.

Shape: So what did your training specifically entail?

JJ: We started a couple of months before the film began shooting with my method of dance cardio before we slowly focused in on her dance moves. In the film, there are two big routines and five shorter ones, which are all very edgy, hard-hitting, and animalistic. Toward the end of rehearsals, we were training four to five times a week for a few hours a day. Jessica was so on it. The routines changed all the way up until the day we shot. We picked out all the music and moves together, and by the time we finished, you would have thought she was a professional dancer!

Shape: Tell us more about your dance cardio workouts that you first brought her through.

JJ: It's a lot of body pumping and sweating. Typically the sessions will run from 60 to 90 minutes. For the first half hour will be booty shaking, hip-hop dancing, leaps, and turning-pretty much sweating your butt off. After you're sweating, we'll go into arms using bands-one of my favorite pieces of equipment. They will wear you out in 10 minutes. Then we'll pick up some light weights and move onto the mat for some intense leg and booty work with the barre. I either use a lot of different equipment or none at all-every workout is fresh so that you work on all the tiny muscles that create an amazing, long, lean, and beautiful dancer's body. We'll end the workout with abs work on the floor or ball.

Shape: Jessica has always been in incredible shape, but what changes did you see in her body throughout your training?

JJ: Jessica loves her body the most when she's dancing. Other people have even mentioned it to her. She tightened up even more. She eats well and takes amazing care of herself but with all the muscular work we did, her abs and booty got tighter, perkier, and stronger.

Shape: What was the atmosphere like on set with director Robert Rodriguez?

JJ: He was so awesome. He gave me the bullhorn so I'd be calling the shots at Jessica like an assistant director. The entire movie was shot on green screen and Jess was so amazing with it. For the actors to be able to do what they do without hardly anything to react to is pretty incredible. She was working 12 to 16 hours a day, most of it dancing-home girl was busy! And boy, can she move. Her body is very fluid and gorgeous and she knows how to move it well. She made me look so good and I'm grateful the producers were grateful.

This sample mini-workout works the core, quads, hamstrings, and glutes, with an emphasis on the outer thighs and hips. Ideally the moves should be done wearing heels (get your sexy on just like Alba in Sin City), but if this is too challenging, try the exercises in your sneakers. The next step would be to try the routine with a pair of sturdy heels while you hold on to a chair or a piece of furniture for balance. Once you feel secure with that, let go and go for it.

How it works: Do each exercise in order.

You will need: Heels (optional)

Winding Squats

Sets: 1

Reps: 3

Stand with feet shoulder-width apart and slightly turned out. Make three clockwise circles with hips while slowly lowering into a squat. Hold the squat for 3 seconds. As you rise up, make three clockwise circles with hips. Repeat, making counterclockwise circles, for 1 rep.

Booty Pop Squat

Sets: 3

Reps: 25

Get in a deep plié squat with feet turned out and knees directly over heels. Maintaining squat, press knees back in a pulsing motion.

Walking Lunges

Sets: 2

Reps: 20

Stand tall. Step right foot forward while simultaneously lifting up onto ball of left foot. Keeping shoulders back, bend knees and drop hips toward the floor without letting left knee touch the floor. Press up with right foot and step left foot forward. Repeat, stepping forward with left leg, for 1 rep. (Take your time with this one. You can choose to do this one with weights or you can just put your hands on your hips.)