Britney Spears' Workout: Yoga, Cardio Training Revealed

Britney Spears is combating reports of her using spray painted abs by shedding light on her "hard" workout regime this week.

The pop superstar kicked of her Las Vegas residency on Dec. 27th when her six-pack abdominal muscles caused controversy.

Several of Spears' stunning costumes during the "Piece of Me" show revealed the singer's bare midriff, and her abs appeared to be painted on with make-up.

However, the 32-year-old singer defended herself against accusations of faking her abs while speaking to Shape magazine about her grueling workouts, which include yoga and cardio.

"I'm doing 90 minutes of yoga twice a week in addition to a lot of cardio- hour-long sessions three times a week with my trainer, Tony Martinez," Spears explained.

Spears is not the only person to vouch for her workouts. The singer's Los Angeles-based yoga instructor, Elizabeth I, revealed which poses worked best for Spears during an interview in June- the Bow, the Boat, and the Camel.

"Sometimes we focus on the core or relaxation, but other times I just kick her butt," I told Shape magazine.

Furthermore, Spears' Las Vegas show requires that the star be in top form.

"This year I have new choreographers," Spears noted. "They're fresh and upcoming guys so their stuff is really hard. It's more rewarding after you perform something that's really hard to do rather than something that you just throw together."

Spears will perform 48 shows, each over 90 minutes-long, at Planet Hollywood Resort over the next two years. Each performance includes Spears' biggest hits as well as songs from her new album, "Britney Jean."

"I'm going to definitely do the greatest hits, but I'm going to have to put some of my new material in it to keep it fresh," Spears explained while on "Good Morning America" in September.

The singer performed over four nights following Christmas and is currently on a month-long break. "Britney: Piece of Me" shows begin again at the end of January.