PEOPLE.COM EXCLUSIVE: Britney Spears Works It During Rehearsals!!

Britney Spears's Circus topped the charts – with a lot of hard work – and now she's promising to do the same in her upcoming world tour. 

In an exclusive rehearsal photo posted to Spears's Web site, Britney claps to the beat in simple, comfortable dance gear. 

Jamie King, who choreographed her 2000 tour, is back on duty, and the singer, 27, looks svelte and toned in a tank top showing off her arms, and even the mom-of-two's tummy! 

The arena tour, her first in five years, kicks off in New Orleans March 3 with special guests The Pussycat Dolls. 

SOURCE: PEOPLE.COM