On the eve of the release of her new album "Bionic", Christina Aguilera is looking better than ever! Christina's favorite thing to do is work those abs. We're not kidding -- she's doing 300 to 500 sit-ups a session, according trainer Tee Sorge tells US Weekly. From warming up on a treadmill before lifting weights to doing backwards lunges with bicep curls, Aguilera is dedicated to working out five days a week to prepare for performances and to stay strong. Start crunching to X-tina's first single "Not Myself Tonight" available for download.