Wth salsa music pumping and whistles blaring in the background, instructor Katy Parker starts twisting her hips. It’s not long before 30 pairs of shoulders are shimmying along with her to the rhythm.

At Zumba class, you can’t help but dance.

“The great thing about it is that you’re having so much fun, you don’t even realize that you’re working so hard,” Parker said.

Parker teaches Zumba classes five days a week at the Lawrence Athletic Club, 3201 Mesa Way. The fitness trend fuses Latin dances like salsa, cumbia, merengue, flamenco, tango – even a little belly dancing – with aerobic exercises to create an hour-long workout.

Parker takes participants between intervals of fast- and slow-paced movements choreographed to 10 songs. The fast intervals speed up your heart rate and get your blood pumping, and the slower movements help tone muscles.

“It’s a lot better than sitting on a bike or running on a treadmill,” says Emily O’Sullivan, a Kansas University student who attends the class at LAC and says Zumba is the reason she and her friends joined the gym.

Zumba isn’t choreographed like other dance routines. The movements fit the rhythm and are not measured in typical eight-count steps, said Adriana Vila, marketing manager for Zumba Fitness LLC and Zumba instructor at the University of Miami Wellness Center. The moves are simple enough that, with help from the music, you can groove through the workout. Participants in Vila’s classes range from college students to an 80-year-old woman.

“You can always moderate the workout to fit how you like it,” says Parker, of the LAC. “If you have bad knees, you don’t have to jump. If you’re pregnant, you don’t have to spin.”

Exploding trend

Nearly 1 million Americans have taken Zumba classes, following the moves of 3,500 instructors, according to Zumba Fitness, which owns the trademark.

Jessica Thompson taught Zumba in a studio attached to her apartment in Kansas City, Mo.

“I had to actually open the doors and move people into my kitchen so they could dance in there,” she said. “It just absolutely exploded.”

Some think markets like Kansas City and Lawrence are embracing Zumba because it is a novelty in areas with less exposure to Latin culture. Others credit zealous instructors.

Colombian native Alberto “Beto” Perez created what has turned into Zumba when he forgot his CDs to teach his fitness class. He had to improvise using salsa and merengue tapes he had in his car. His on-the-spot creation was a success, and he started teaching Zumba in the United States in 1999.

Since starting Zumba in 2005, Parker has lost more than 30 pounds and has been able to keep it off.

“Besides being aerobic, you’re using all the muscles in your body,” Parker says. “It really tones your body up.”

Some dancers say they can burn up to 700 calories or more in one session – an amount that will shed about one-fifth of a pound. Such results are unlikely for beginners, however, said Richard Cotton, chief exercise physiologist with MyExercisePlan.com, a San Diego-based exercise Web site.

“Someone who gets off the couch after 20 years and goes to a Zumba class – they’re not going to get that result,” he said.

Staying power

People who keep coming back to the LAC classes say Zumba makes exercise fun and keeps them energized about the prospect of staying in shape.

“It’s wonderful. I come everyday,” says Ngondi Kamatuka, a Lawrence resident who has attended Zumba classes at LAC since they started in January.

Zumba teachers must be certified by the Zumba company to learn the basics of teaching classes. But teachers have the ability to modify movements and music to shape their own routines. Parker likes to keep her class fresh by using music other than just Latin rhythms. She has used everything from rhymes by the rap group Outkast to country songs.

Zumba is the latest page in the history of musical fitness.

Aerobics, a free-form, 32-count routine that follows one song to the next without interruption, arrived in the mid-1970s. The more dance-oriented Jazzercise, choreographed to specific contemporary songs, followed.

Next was step aerobics, where a box or step is used for step-up, step-down and circle-around exercises. And then there was spinning, where exercisers hop on stationary bicycles and pedal to music up and down imaginary hills.

Observers think Zumba may have staying power.

“The music is so peppy. It’s happy music,” said Jodai Saremi, assistant editor at American Fitness Magazine, a trade journal published by the Aerobics and Fitness Association of America. “As long as the Zumba company keeps coming up with new music and choreography, people are going to be interested.”