BODY WATCH : Child’s Play : What with juggling acting careers and school, celebrity kids have to hard work at goofing off. That’s where the fun-loving pros from Personal Edge come in.

“Lunch!”

Many folks on the “Home Improvement” set let out a last camera-ready breath before settling in to chew the fat, or fat-free as the case may be. But one cast member, Taran Noah Smith, 11, grabs a salad and heads out onto the Disney lot.

By a fenced-in court under a sign that reads, “Child Actors Break Area: No one over 16 allowed (NO EXCEPTIONS!),” he’s joined by his older sitcom siblings--13-year-olds Jonathan Taylor Thomas and Zachery Ty Bryan. Soon the leading laddies are playing a gonzo game of basketball, having forgotten about scripts, lines, marks and makeup in a finger-jamming scramble for the hoop.

But . . . timeout!

What are two grown-ups doing in the picture--slamming and dunking, stealing the ball the way they are? “NO EXCEPTIONS.” Exclamation point. Remember?

Meet Vikki VanHoosen, 36, and husband Angel Aguilera, 32, personal trainers to Hollywood’s rising stars. As for the sign, these adults are really just two overgrown kids--a point that may have something to do with their success.

It was three years ago that VanHoosen started Personal Edge, a company providing fitness for children and teen-agers in the industry. The “Home Improvement” boys were the guinea pigs; now VanHoosen and Aguilera train prime-time pixies all across the airwaves, working with such shows as “Me and the Boys,” “Boy Meets World,” “Baywatch” and “Thunder Alley.”

“I can already feel the difference in my body and in my mental outlook,” says one of the newest clients, 16-year-old Tatyana Ali from “Fresh Prince of Bel Air.”

Obviously these are not your ordinary kids. With high-stress careers and school to juggle while keeping their cherubic chins up, they’re beyond any fast track; they’re going at e-mail speed.

“One of the greatest difficulties for children who are holding down the job of an actor is normal child development,” says Gayle S. Maffeo, vice president in charge of production and administration for Wind Dancer Productions at Disney. “Kids need to play and we like to deal with kids who behave like real kids.”

That’s the philosophy behind Personal Edge, where a visit to a place such as Virtual World (“great for hand-eye coordination,” Aguilera says) is just as important as a session in the gym or a talk about vegetarianism. It’s hardly your “have-dumbbells-will-travel” trainer gig. These fitness pros are much less interested in buffing up budding bodies for the box office than teaching a healthy, active lifestyle.

VanHoosen and Aguilera are on call around the clock, constantly engineering family-style outings--horseback riding, ice-skating, mountain biking, fishing. They even gather their charges during hiatus to take ski trips or to go white-water rafting.

“We try to include as many different activities as possible so the kids see they don’t have to do pushups and sit-ups to get a workout,” VanHoosen says.

Typically, she and Aguilera show up on the set during the day to help the kids burn off excess energy with a kickbox-funk workout, a game of soccer or perhaps a roller-blading session around the lot. The evenings are usually girls’ night out with VanHoosen, who shepherds the teen actresses to various classes around town, or teaches one herself, coaching them along the way on proper form and exercise mechanics.

VanHoosen encourages her stars to act as role models for all their tube-tied fans--America’s young and resting who have abandoned biking and basketball for channel surfing. According to data collected regularly by the Centers for Disease Control and Prevention, almost half of students in grades 9 through 12 are not enrolled in physical education classes. And of those who are, attendance falls off; a third of all ninth-graders say they go daily compared to only one in 10 seniors.

The inactive kids are the ones VanHoosen ultimately wants to reach. Along with attempts to get fitness programming onto one of the school channels, Personal Edge is now producing a series of kid fitness videos featuring her star clients, starting with “Boxarate.”

“The kids out there aren’t going to listen to me, an old fart,” VanHoosen says. “But they will listen to Jenna (von Oy of ‘Blossom’) and Jonathan.”

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It was by way of the Golden Door spa in San Diego County that VanHoosen got plugged into the biz-kid set. The former tennis pro, who had spent years directing programs for the YMCA, was working at the spa when one of the guests asked if she’d move to Los Angeles to become her personal trainer. The guest was Carol Burnett.

Through Burnett, VanHoosen wound up who’s-whoing it until she connected with Wind Dancer’s Maffeo, consulting producer on “Home Improvement” who, in turn, introduced her to the boys.

“The kids would have so much energy, they’d tend to start taking it out on everybody else,” says Maffeo, explaining why she decided to hire a trainer. “Their attentiveness and performance on the set improved a lot after Vikki joined us.”

It’s been three seasons now and the chemistry is still going strong. Today, with many other young actors on the Personal Edge client list--and a few older ones as well--Aguilera, originally a stockbroker, now helps his wife run the show. The two Peter Panners have definitely been bitten by the youth-fitness bug. Says VanHoosen, who turned down six weeks in Switzerland training Aerosmith: “I would have really enjoyed going, darn it, but I couldn’t leave the kids.”

Apparently she’d rather get roughed up and splattered in a full-out game of Paintball Wars. Both she and Aguilera took 25 teen-agers on a trip to Corona to do just that one recent weekend. (“It’s very physical,” VanHoosen says. “You have to run, hide, jump and duck while keeping your eyes open to everything going on around you.”)

The girls were still talking about it two days later, show-and-telling their war bruises in VanHoosen’s evening “funkarate” class--after which the conversation turns to the music in Eric’s car and other important matters. Their mouths never stop moving, but VanHoosen lets them gab--as long as they keep working out. They don’t get to be teen-agers very often, she shrugs.

Sure enough, at the end of class life snaps back into production mode. “My mom paged me forever ago and I never called her back,” says Jenna, rummaging for her cell phone. Tatyana Ali fishes hers out too.

Someone brings swatches of material for the girls to look over. Arrangements are made, calendars checked. Finally, they file into the parking lot still power-chatting--words like photographer and agent overtaking the giggly talk of butts and boys.

VanHoosen reminds them that tomorrow evening is their first yoga class. Looks like they’ll be needing it.