Pop superstar Britney Spears is currently gearing up for her 'Piece Of Me' Las Vegas residency, which will begin on December 27, and has been working out hard at the gym to get herself fit for the high-octane concerts. 

Tony Martinez, Spears' award-winning trainer, told RadarOnline.com that she has been putting in maximum effort to ensure she's in the best shape she can be in for the extensive run of dates:

"She is working as hard as she can, and it is paying off. She's using all her energy right now to get ready for her 90 minute Las Vegas show. She wants to be in the best shape possible, and she is very happy with her body right now. She is in a really good place, and I'm so proud of her."

Martinez added that the 'Till The World Ends' beauty has been learning that it's not necessary to spend hours in the gym and, instead, has been doing short bursts of intensive exercise: "My workout motto is work out smarter, not longer."

"There's no need to run on the treadmill for two hours. I've shown her ways to sculpt her body that take less than 20 minutes. Now she's loving these quick workouts."