The Pro: Derek DeGrazio, L.A.-based fitness expert and trainer.
Core Client: DeGrazio taught this move to Britney Spears while traveling with her on last year's Femme Fatale tour.
The Steps: 1. Sit on a mat with your knees bent, feet flat and arms by your side.
2. Bend your knees and lift your feet off the mat until your shins are nearly parallel to floor. Lean back 45 degrees so that your torso and your thighs form the letter V.
3. Hold a 6 to 10-pound medicine ball (or a dumbbell, or a jug of OJ) close to your chest with your elbows out.
4. Rotate your upper body to the right so that your left elbow is above your right hip. Then rotate to the left in the same way.
5. Do 3 sets of 30.