Pics of Brit taken on March 23rd (Star)

Britney Spears is trying to get her pop star body back. According to an insider, she does a 2 hour routine at Bally's complete with 22 minutes on the elliptical, plus crunches, weights and the treadmill.

Her former manager Larry Rudolph on Brit's transformation: "She's in great shape. I mean, really great shape. I see huge improvements with her. She's exercising. She's eating great. These are the things she needs to be doing right now. She's well on the road to being the Britney everyone knows and loves."

A source told Life & Style: "She's become very aware that she doesn't look like she sued to, and she's working hard to do something about it."

The source added that Brit's been working out 5 days a week, avoiding junk food, getting manicures, and using a tanning bed at home.

Britney (with nice nails) after a workout at Bally Total Fitness gym in Culver City (04/23/08).