In anticipation of rocking our favorite two-piece this summer, we asked trainer Harley Pasternak how he's helped Lady Gaga, Katy Perry, and Jennifer Hudson tone their abs. "You've got to do all three of these moves if you want to look great from every angle," he insists. Do three sets of 20 for each, three times a week.
Double crunch: Lie on your back, hands behind head. As you bring your chest up (like in a regular crunch), lift up your knees and touch your elbows to them.
Trunk twist: Sit on the floor with your knees bent, feet on floor in front of you; look straight ahead and lean back 30 degrees. Holding a medicine ball (or water- melon), slowly rotate your upper body to the left, then to the right.
Side bend: Stand upright with an 8- to 10-pound dumbbell in your right hand hanging down at your side and your left hand against your left temple (as if you're saluting). Slowly slide the dumbbell down your right side as you lengthen your left arm and stretch it over toward the right. Slide the dumbbell back up as you return your left arm to original position. Repeat on other side.