DES MOINES, Iowa (AP) -- There were wild arm swings, sharp robotic turns and pulsing fist pumps.

Michelle Obama busted out a few new moves Thursday to mark the second anniversary of her campaign against childhood obesity with a few new friends -- 14,000 or so, it turns out.

The first lady rocked out with thousands of sixth- to ninth-graders at a Des Moines arena on the first stop of a three-day trip to highlight her "Let's Move" campaign.

It was a giant pep rally for eating right and exercising, complete with confetti, balloons and a towering birthday cake made out of fruits and vegetables.

The first lady and crowd revved up by doing the Interlude, a dance that started in a dorm room at the University of Northern Iowa and went viral from there.