For Christina Aguilera, preparing for her role as a singer and performance artist in her first film, Burlesque, is clearly doing her body good! “I’m bringing my A-game and taking it very seriously,” she tells In Touch. Her trainer of five years, Tee Sorge, reveals that the 29-year-old star is rehearsing 14 hours a day and says a lot of that time is spent dancing. “She’s tremendously happy and feels really strong,” Sorge tells In Touch. The busy mother is also squeezing intense weight-training sessions into her busy schedule two to five times a week. “We want to make sure she doesn’t lose her muscle mass or too much weight,” her trainer says. So, Christina starts with a 10-minute warm-up on the treadmill and then goes straight into lifting weights. “We work the entire upper body by doing everything from bicep curls to tricep dips,” says Sorge. “Christina does three sets of each exercise and uses weights ranging from five to 15 pounds.” But her favorite thing to do is work her abs, and Sorge reveals the star does 300 to 500 sit-ups a session! When it comes to her diet, Christina has always been “good” says Sorge, but now she’s eating exceptionally healthy. “We took out all the whites, like white rice and white sugars,” says Sorge. “She’s sticking to whole grains and lean proteins.” Luckily for her, she has one cheat day a week. “Her goal now is just to be fit,” Sorge tells In Touch.