DO YOUR OFFSPRING spring off the walls these days? Cartwheel through the living room? Bounce off mattresses? Rescue yourself and them from cabin fever and drive over to George Mason University's Patriot Center Saturday or Sunday for a look at young competitors from 19 countries who have harnessed that same energy and used it to make themselves international gymnastics champions. Most will almost certainly represent their nations in the 1988 Olympic Games.

If your kids need further convincing, tell them this: Olympic gold medalist Mary Lou Retton won this competition -- called the McDonald's American Cup -- three years in a row (1983, 1984 and 1985). And Romania's Nadia Comaneci began her legendary career when she scored her first perfect 10 in this competition, the largest and most prestigious international invitational gymnastics event in the United States.

Beginning at noon on Saturday, more than three dozen gymnasts will compete -- three men and three women from the host United States, one man and one woman from each of 18 other countries, including the Soviet Union, China, Japan and Romania. At 2:30 Sunday, the best eight men and best eight women will continue toward the top prizes, with no points carried over.

The U.S. men on tap are Olympic medalist Tim Daggett, 23, winner of the 1985 American Cup; Daggett's teammate from UCLA, Brian Ginsberg, 19; and Southern Illinois graduate student Brian Babcock, 25.

The American women's team is especially young: Sabrina Mar, 15, current women's national champion, a straight-A student from Marina High School in Monterey Park, Calif.; Melissa Marlowe, 14, an eighth-grader from Salt Lake City; and Kristie Phillips, 13, of Baton Rouge, La., studying in Houston with Retton's coach, Bela Karolyi.

Phillips is the yougest American ever to compete in the American Cup, but she's not the youngest person in the competition. That honor goes to Venezuela's Oriana Mendez, an 11-year-old sixth-grader. A gymnast for just five years, she is said to prize her collection of Snoopy toys.

Other very young competitors are Luisa Riberio of Brazil, Jaynery Freula of Cuba, and Sandrine Villanne of France, all 13.

As good as these competitors are, they couldn't make the Olympics if the games were being held this year. They'd be too young. An athlete must turn 15 during the calendar year to compete in the Olympics.

Besides getting a look at current international gymnasts and a preview of rising stars, what should you and your kids look for?

Susan Polakoff of the United States Gymnastics Federation says this is an excellent spectator event because there are no compulsory events. "You don't see the rigid routines, hear the same floor exercise music 85 times in a row. It's all optional. There's more drama, more flair -- the lead changes hands after each round. It's really exciting to watch, even if you're not a gymnast."

It's also a good place for aspiring gymnasts to pick up pointers. Milan Stanovich, director and coach of the Karons Gymnastic Club in Fairfax, says he's told his students "to watch how the gymnasts prepare themselves when they go up, how they react when they hit -- or when they miss -- a routine. What attitudes they have when they're competing. Probably their coaches don't say that much to them -- at that level, they're self-supporting people -- but we want our students to look at the way they're handling themselves throughout the competition."

Polakoff added that "this is going to be a world-class meet, and it's the first time the Soviets have been here since 1983 . . . Now's our chance to see what the Eastern bloc countries have been up to . . .It's also a chance for spectators to see who is hot, who's going to be the hot Americans."

Among those Polakoff will be watching:

* Daring Soviet gymnast Alexandr Tikhinkikh, 24, known for inventing a vault that the Federation Internationale Gymnastique ruled too dangerous for male competitors to use. The outlawed move is a round-off back flip onto the vaulting board and back handspring up to the horse, then a back flip off the hands with a full twist. The federation allows it for women, because they come at the horse from the side.

* Russia's female entrant, Irina Baraksanova, 16, defending Soviet champ on the balance beam and fourth going into the all-round finals at the World Championship in Montreal last November (her coach pulled her from competition because of injuries).

* China's female entrant, 16-year-old Zeng Yingzi, who is best in the vault and uneven bars.

* China's male entrant, Wang Chonsheng, 19, best on the high bar and pommel horse.

* Marlow of the United States, first all- round and first on balance beam at the American Classic in Colorado Springs last year; "very strong on uneven bars and balance beam."

* Phillips, who coach Bela Karoyli has said is even better than Mary Lou Retton was at the same age.

* Mar, America's top all-around women's gymnast and best U.S. gymnast at the World Championships; excels in uneven bars and floor exercise.

* Daggett, defending American Cup men's champion, whose perfect 10 routine on the horizontal bar clinched a gold medal for the American men's team in the 1984 Olympics; best on pommel horse (Olympic bronze medalist) and horizontal bar.

CBS will televise the meet live at 4:30 Sunday on Channels 9 and 11.

THE McDONALD'S AMERICAN CUP -- Saturday, noon to about 5; Sunday, 2:30 to about 5:30. Tickets: $8 and $10 for Saturday; $10 and $12 for Sunday; $12 and $16 for both days; $2 discounts for children 12 and under and senior citizens; $2 discount coupons available at area McDonald's. To charge tickets through TicketCenter, call 432-0200.

To get there: From the Beltway, take Braddock Road (Exit 5) west about six miles to the George Mason University entrance on your right. Free parking.

Patricia Brennan last wrote for Weekend on fairy tale dramatizations.