Rihanna

Happy birthday, Rihanna! The singer turns 25 today, and to celebrate the milestone, we're taking a look at how she stays fit.

She fits it in: Rihanna worked with trainer Ary Nunez for years, taking her whenever she traveled on tour to make sure she couldn't slack off with her workouts. Ary was on call with workouts that were a mix of martial arts, dancing, and calisthenics, no matter what the time. "We train when she’s ready . . . even if we’re on the road, and it’s 2 a.m. in the morning. I’m on call 24/7 with her," Ary said in 2012 about training Rihanna.

She steps it up: While training for her role as a hard-core military officer in last year's movie Battleship, Rihanna didn't shy away from intense bootcamp classes. She worked out alongside real-life Navy officers with push-ups, drills, and weighted sandbags to help get into shape — and into a tough military mindset — for the movie.

She loves cardio: When Rihanna wants to slim down, she ups her cardio, saying in 2008 that she uses it to keep her legs from bulking up. Now, when she's not traveling, Rihanna bumps up her cardio to 30 minutes, five days a week (from her usual three-day-a-week routine), says trainer Harley Pasternak. Her favorite cardio workouts include the stationary bike, cycling, jogging in place, jumping jacks, and jump roping.

She complements with a healthy diet: "If I exercise every day for a week, I can drop several pounds. If I diet, I see even faster results," Rihanna has said. Harley says the singer sticks to a diet of five small meals a day.

Let it be heard: Rihanna has inked a deal with MAC Cosmetics, which includes four collections, aptly named RiRi Hearts MAC, to be rolled out over the next year. The news comes fresh off the success of the singer's first runway show at London Fashion Week . . . as well as on her 25th birthday. Rihanna told WWD that the unprecedented deal for both was "a no-brainer."

The first product to drop will be a lipstick dubbed RiRi Woo, which was inspired by MAC's Ruby Woo, Rihanna's favorite shade. MAC will release the shade to coincide with the Grammy winner's stint at the Barclays Center in Brooklyn on March 4 and 5, as part of her Diamonds Tour. The cosmetics giant will open a pop-up shop at the March 4 show to showcase the line. RiRi Woo will be sold at Rihanna's concerts as well as online and in conjunction with all four collections. Get the scoop on the full collaboration when you keep reading.

Although the little black dress is a seasonless closet staple, Rihanna, Amanda Seyfried, and Jennifer Lawrence have all opted for a little orange one instead. And let's just say, the bold color swap has us second-guessing our own current go-to dress choices. Rihanna skipped the Valentine's Day pink palette for an orange wrap dress in LA, while Amanda styled a silk Roland Mouret confection with ankle-strap Jimmy Choo pumps, and Jennifer went sexy-sweet in a Stella McCartney cutout dress in London. Not only does this high-octane hue complement most skin tones, but with a few easy styling tips, the LOD can be the star of your wardrobe year-round. Take a cue from these trendsetters, then shop our editors' picks to beat the Winter blues.

• The Trendsetter: Rihanna's gold ankle-strap sandals lent a minimalist touch to her orange wrap dress. To inject a similarly cool — but never overdone — tilt to your LOD, add a leather jacket, caged sandals, and a statement necklace into the mix.
• The Sophisticate: From the cowl-neck collar to the ladylike hemline, Amanda's Roland Mouret dress evoked a seriously chic vibe. Follow her lead and work your orange dress with ankle-strap sandals, a black belt, and dainty jewels, and then top it off with a plush fur coat to further the sophisticated glamour.
• The Siren: Jennifer's bright orange Stella McCartney dress featured the perfect amount of sex appeal. Mimic her party style with a cutout LOD, metallic pumps, and an effortless updo.