What has purple legs and a green-striped torso, wiggles all over and attracts lots of attention?

It's Wanda Bamberg, the most popular slimnastics teacher at the downtown YWCA.

With her large gold earrings, bright lipstick and flashy leotards, Bamberg gyrates, marches and dissolves into many different motions during her classes.

She wrings tireless obedience from her supple body, and those of the students striving to imitate her. The whole room seems to vibrate with energy during her 45-minute classes.

Bamberg, 27, one of 15 slimnastics instructors at the Y, also brings a sense of individuality to her students, remembering their names, in addition to cajoling, exulting and advising them with her motto:

"Ladies, you have only one body to live in, so keep it alive . . . look and feel better every day. . . for you are the rising star."

So many people want to bend, stretch and get aching muscles with Bamberg that Sheila Drohan, the Y's director of health and recreation, said she had to move most of Bamberg's classes from a small classroom to the large gymnasium.

For the first six months of this year, according to the Y's attendance charts, Bamberg's classes ranged in size from 40 to 50 students. The slimnastics instructor with the second highest attendance had classes that averaged 30 to 40 students, according to the records.

The majority of the teachers had fewer than 30 students per class. Slimnastics, the most popular course at the Y, is given 36 times a week.

"Wanda has a real dynamic personality," Drohan said. "She can encourage all participants to get involved and excited about exercising." And, she added, "Wanda remembers when people haven't been to exercise," which encourages people to stay in an exercise program.

When people sign up for the classes they simply select the time they want. The names of the instructors are not given. But word travels as to which classes Bamberg will teach, and "her classes are usually the biggest," Drohan said.

Judy Schimmel, 41, who has been coming to slimnastics for five years and is a regular in Bamberg's classes, said: "No one can get you to work as hard and no one communicates as well as Wanda when she says, 'Let's do it.' She's charismatic."

The strains of Sibelius, Beethoven and Gershwin, as well as Lip Co.'s "Funkytown" echo through Bamberg's classes, providing the rhythms for the dance and exercise routines.

She strives to make the exercises fun because "one of the greatest sources of my pride in my job is seeing people happy and being themselves," Bamberg said. "And I'm a believer that if you are going to help somebody, you should give them something they can go away with."

At one recent class Bamberg was, as usual, at the door greeting the women as they entered. "I recognize those leg warmers. I saw you at the 12 o'clock class today," she said to one.

To another, wearing a black leotard and yellow tights, she said, "You look like a bee." During the session, she constantly encouraged the class, with "Keep that stomach in" and "Be sure to give it all you've got this time."

Bamberg, a native of Columbia, S.C., came to Washington in June l980 and went to a work in a personnel agency. But she soon became bored and started overeating.

Formerly a model with a size-5 figure, she decided to get back to exercising. After a short stint as an instructor at a local reducing salon, she came to the Y in January 1981. She also runs her own business--the Wandawoman Aerobics Exercise and Nutrition Program--and teaches exercise classes at the Academy of Notre Dame, a Catholic girls' high school at North Capitol and K streets NW; the Tanbridge School of Fashion and Fine Arts in Marlow Heights; and the Mount Gilead Baptist Church at 13th and Q streets NW.

Debbie Blanc, 29, another Y regular, said she likes the way Bamberg goes around to check on people exercising in her class. "She's pleasant, funny and serious at the same time," Blanc said.

Mariana Jessen, 72, who has attended exercise classes in New York and here for 26 years, agreed. "Wanda is the most dynamic human being I ever met," she said. "I love her warmth and her feeling of support. She makes you feel special."