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HAYDEN PANETTIERE, 23
The Nashville star sure isn't singing the blues in this purple triangle bikini top and tassled bottom, which she wore in Miami. Exercising is a regular thing for the petite actress, but not everything: "If I push myself too hard, my brain starts thinking of working out as a burden instead of something I enjoy," she tells Self.com. "Three times a week is a really healthy amount."
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JULIANNE HOUGH, 24
It takes confidence and a toned body to wear a white bikini, and Hough has both during a vacation in St. Barts. To keep fit, Hough has learned that fitness classes are her best friend. "I do really well in a setting where I’m told what to do," she says, "because if I'm by myself, I go to the gym and I do fifteen reps, and then I’m like 'Oh, my e-mail. I need to make a phone call!'"
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KENDRA WILKINSON, 27
The former Splash contestant proves she's "cut out" for sexy swimwear while hosting a Hawaiian Tropic bash in Las Vegas in a smoking-hot white one-piece. Besides the gym, Wilkinson maintains her Playboy proportions with tennis, basketball, kayaking and snowboarding, reports Shape.com.
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ASHLEE SIMPSON, 28
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JESSICA ALBA, 32
A body as stunning as Alba's, who showed it off in a blue-and-orange bikini in St. Barts, is the result of lots of hard work, even if its owner would rather be doing something else. "Sometimes I do sprint intervals [on the treadmill] just because I hate working out," Alba tells Women's Health recently. "That's so much better for me than anything that's repetitive."
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The pop star's ripped physique nicely fills out a striped two-piece on a walk through the Miami surf. Getting into such spectacular shape takes a lot of discipline and, surprisingly, sprinting. Pink tells Shape.com, "[It's] my favorite workout that takes care of the whole body – it's the most results I get." And though she admits to craving carbs like pizza and pasta, there are "three healthy foods always in my diet": couscous, broccoli and salmon.
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KOURTNEY KARDASHIAN, 34
The eldest Kardashian makes a splash on a Mexican beach seven months after giving birth to daughter Penelope. Though she gained 44 pounds during her pregnancy, the reality star lost it all through disciplined eating and regular exercise, including posterior-focused moves that targeted the back, triceps, glutes and hamstrings.
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REESE WITHERSPOON, 37
The actress wears a flattering navy ruched one-piece on a Hawaiian beach, just three months after giving birth to her third child. And though she's an avid runner, Witherspoon told Extra she's in no rush to get back to her post-baby shape: "You just have to be gentle and patient with yourself and slowly get back to your health."
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EVA LONGORIA, 38
Working out four times a week and sticking to a diet of plenty of fruit and veggies (and, we're sure, the occasional splurge at her new Las Vegas steakhouse, SHe), Longoria cuts an enviable figure in an attention-getting orange bikini in Puerto Rico.
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KATE BECKINSALE, 39
What's black and white and fit all over? Beckinsale, who sports the classic color combo for an afternoon of sunbathing in Mexico. It's no wonder she was named Esquire's Sexiest Woman Alive a few years ago. To get the British beauty's incredibly toned booty, her trainer Mandy Ingber, tells PEOPLE they work on yoga poses with an emphasis on squats, lunges and plié squats.
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GABRIELLE UNION, 40
Forty looks fabulous on the actress, who strolls a Miami beach in a tiny bikini topped with a straw hat and shades. To keep her body in model form, she does cardio and Pilates; for glowing skin, it's all about H20. "I drink a gallon of water a day," she tells Glamour.com. "I bought two-quart containers and I fill them with my Brita water and I suck it down."
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BETHENNY FRANKEL, 42
The newly single reality star sports a green print bikini and a toned physique while frolicking in a Miami pool. The secrets of her success? Yoga and her own exercise DVD, Body By Bethenny, which features her favorite move, the wide leg forward bend. "It stretches and elongates the back of your legs," she says, adding, "What a release!"
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JENNIFER LOPEZ, 43
Not many fortysomethings flaunt their curves in flashy bikinis but then there's only one JLo, who takes her anything-but-mellow yellow bikini poolside in Miami. Regular hour and a half workout sessions, five days a week with Maria Kelling, a Tracy Anderson Method trainer, keeps the star in tip-top shape. "She's so dedicated and consistent," Kelling tells PEOPLE.
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NAOMI WATTS, 44
The Aussie actress's figure is spot on as she heads into the waters of St. Barts in a one-piece suit that flatters her petite frame. She credits her shape to good genes, exercise and not depriving herself. "I don't starve myself, because I start denying myself, that's when I ant to eat most of all," she told PEOPLE.
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KELLY BENSIMON, 45
The former star of The Real Housewives of New York City models a classic black bikini on a beach in Naples, Fla. Sticking with other classics – squats and lunges – gives her a leg up on the competition. "They just really tone up the inner and outer thighs and lift the buttocks," she tells Shape.com. "When your butt muscles are toned, your legs look leaner."
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ELLE MACPHERSON, 49
Even today, the five-time Sports Illustrated swimsuit issue cover girl lives up to her nickname "The Body," which was on display in Formentera, Spain, in a barely-there bikini. How does she do it? With lots of water, seven hours of sleep a night and doing varied activities like tennis and hiking that don't take "hours and hours and hours," she tells AccessHollywood.com. As for her diet, "When I make [food] choices, [it's not] 'Is that gonna make me thinner?' It's, 'How do I feel when I eat that?' "
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KELLY PRESTON, 50
Why bother sweating it out in a skimpy bikini when you look this good in a one-piece? During a family vacation in Hawaii, Preston wears a classic suit in a slimming solid. Hard to believe she gave birth to son Benjamin two years ago when she was 48!
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JULIANNE MOORE, 52
All's fair for the porcelain-skinned movie star, who pairs a bikini top with protective board shorts to take a dip in the waters of Hawaii. According to fitnessmagazine.com, the actress's trick to keeping extra-toned is doing squats, lunges, side kicks and roundhouse kicks and focusing on one muscle for three sets of four exercises.
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EMMA THOMPSON, 54
While filming a movie on a Cannes, France, beach, the two-time Oscar winner confidently shows off her shape in a maroon one-piece but keeps her bottom stylishly under wraps with a colorful sarong. "I [run] almost every day, partly because I want to drink wine and eat what I bloody well want, but, because around 40, everything changes," she tells London's Daily Mail.
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