WALK AWAY FROM YO-YO-ING

MARINA managed to shed most of the weight before becoming pregnant again — with Tyler, now eight. Two years and a third pregnancy later, she was diagnosed with placenta previa, a potentially life-threatening condition. On doctor’s orders, MARINA was confined to bed for four months. “That destroyed my body,” she moans. After giving birth to Tess, now six, “the only thing I could do was walk. I wasn’t allowed to dance.” But again, she was determined to keep going. “I bought a treadmill, put it in the bedroom and walking became the workout for me.”

Soon MARINA was back in the production studio. But though she had worked behind the scenes as a writer, voice-over artist, casting director and producer for thousands of commercials, she missed being on the stage. So at age 37 MARINA started writing, producing and performing dance music for her company’s label, MRK Records. She also choreographed and starred in a live show — complete with special effects and a phalanx of backup dancers — that she brought to the hottest nightclubs in New York City.

Hitting the big 4-0 hasn’t slowed down MARINA, who is known professionally only by her first name, like one of her idols. “Cher, at age 53, proves to those in the record business that a truly talented artist is ageless,” she says reverently.

MARINA feels she is as fit today as she was at 20, when she spent her nights dancing at Studio 54 and CBGB. Dance rehearsals and regular toning exercises keep her tummy flat and her weight between 115 and 120 pounds. But day to day, “the only consistent thing in my life is walking,” she insists.

Each morning, headphones and sneakers on, MARINA struts out from her apartment building on Manhattan’s Upper East Side near 79th Street. She whips through the 42 blocks — almost three miles — to her offices on Seventh Avenue and 47th Street in 35 minutes. Some days she even beats Roy to their studio. And he drives there.

Now as she strides along she listens to her own dance music on her Walkman. Last year she released her first full-length CD, Um-Lotty-Da, featuring her own original songs. Under Her Covers, an album of remakes of classic pop hits like “Foolish Games,” “Do Ya Wanna Dance?” and “Shame, Shame, Shame,” will debut in March.

She checks her tapes as she strolls. “If it’s not doin’ it for me, I fix it. It has to pump me and make me go, because, hey, I’m lazy like everyone else. I just want to sit and eat hamburgers all day.”

MARINA creates her dance-club music with a specific audience in mind: moms like her. “We originated and danced to this style of music in our 20s. Yet I felt that nobody was producing music specifically for women my age — radio-friendly music with lyrics that we can listen to with our children, that are not talking about anything dirty... positive messages that we can pop in and exercise to.

“We’re all balancing work and a personal life. We don’t have the time or money to join a gym. So we walk, we run, we treadmill. What kind of music do we want to listen to? Dance music. But most of it is so mundane — I wanted to produce something women could sink their teeth into.” So she wrote tunes like “Strut” to encourage them to get moving and “Best Friend for Life” to celebrate women’s friendships.

MAKING FITNESS FUN

MARINA herself may not make it into the gym these days, but her music does: Jazzercise licensed several of her songs, including “Strut,” to use in its aerobics classes. Her version of the Annie Lennox hit “Sisters Are Doin’ It for Themselves,” with singer Hazell Dean, throbbed over the loudspeakers at Madison Square Garden to introduce the New York Liberty, the women’s pro basketball team, throughout its 1999 season.

While MARINA targets her music for her peers, she’s also doing her best to get the next generation moving. Remembering her own childhood resistance to exercise, she makes fitness fun for Justin, Tyler and Tess. They do the usual whirl of gymnastics, soccer and basketball after school, but at home MARINA plans strolls with a destination — to the movies, a park — something they can do together. “I will walk them and they aren’t aware of it.” Even the treadmill is plunked down in front of the TV — to watch, they have to walk. “I trap them that way,” she says slyly. “If they knew what I was doing, forget about it!”

Morphing from overweight mom to dance-music diva, MARINA is an inspiration to other women trying to make their dreams come true. As she sings on “Sisters Are Doin’ It for Themselves”: “We’re standing on our own two fee/And ringing all our own bells.”