Part aerobics class, part dance party, Zumba classes give Jazzercise a 21st -century update as participants shake and shimmy to world music — simultaneously increasing their heart rates and working abs, hips and thighs.

  Zumba was created in 2005 when Colombian aerobics instructor Beto Perez forgot his music for class one day and improvised a routine using salsa CDs he had in his backpack. Today, Zumba is marketed as an upbeat, Latin-inspired dance class that allows participants to burn calories without watching the clock.

  "First of all, it's an emotional relief," says Tatyana Galovkina Parker, who teaches a weekly Zumba class at the Jewish Community Center Uptown (5342 St. Charles Ave., 897-0143; "It's also an energy booster."

  Parker says she has seen Zumba's great effects on her students' mind, body and spirit. Zumba classes involve hip gyrations that exercise abdominal muscles, as well as footwork that works hips and thighs. Parker believes Zumba builds confidence along with muscle tone, because students learn dance moves to show off when they go out on the town.

  Parker, who trained as a ballet dancer in Russia and later toured as a Russian folk and ballroom dancer, enjoys creative flexibility when leading Zumba classes. She incorporates ballet and ballroom moves into routines, sometimes adding a twirl or sashay to a cha-cha or merengue step. She encourages students to learn the moves at their own pace and "just have fun." Class begins with the following warm-up designed to ease everyone into the steps. Like any dance, each move is performed in time with music.