To reprise her role as stripper Nancy Callahan in Frank Miller's Sin City: A Dame to Kill For, "our focus was on leg strength and endurance," says Jennifer "JJ Dancer" Johnson, Alba's trainer and choreographer for the film (out Aug. 22). Along with dance cardio, the star used resistance bands to sculpt her glutes and did lunges in heels, which "made her legs lean and defined," Johnson says.


At first "she was a tiny bit shy. She's not a dancer," says Johnson. But after a few weeks "I'd have her winding, grinding and gyrating like a pro!" An added benefit: "Doing body rolls worked her abs, because you're pulling in from your core." Their three-hour sessions, up to five times a week, paid off for the mom of two. "Jess said her body looks the best when she's dancing," says Johnson.

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  • CONTRIBUTOR Michelle Ward.