Ethan Wilansky, 25, used to be afraid of heights. Dave Andersen, 26, used to be fat. Now, Wilansky regularly performs six feet off the ground, and Andersen looks like he could bounce a quarter off his stomach.

Together, these Prince George's county residents are the two-time elite men's pair national champions in sport acrobatics and this year are ranked fifth in the world. They are also the first U.S. men's pairs team to qualify for the World Cup in five years. Their October performance in Baton Rouge, La., at the World Cup was recently shown on ESPN.

"Most people don't seem to have any experience seeing anything like us," Andersen said.

Sport acrobatics is unusual in that it uses the body of another person or persons as "living apparatus." The sport is related to the acrobatic acts in the circus, but in international competition,there are more than 17 events for pairs, trios and quads composed of men, women and mixed groups.

Invented in the ancient Chinese court, competitions were first held in the Soviet Union in 1939, but the sport did not have a national meet in the United States until 1976. Sports acrobatics has an international federation and a branch in the U.S. It will be exhibited at the 1992 Olympics and will a competitive sport in the 1996 Olympics.

"They are two of the most dedicated people I've seen," said their coach, Bob Ouellette, who is also coach of the Maryland-National Capital Parks and Planning Commission's Prince George's Gymnastic Club. The pair practice there and Andersen works at the club.

Being dedicated to and performing at the elite level in a lesser-known sport, however, is not easy.

After studying the sport in New Orleans, where there are some of the few coaches in the U.S. who specialize in acrobatics, Andersen, who is 5 feet 11 and 182 pounds, decided to come back home and train as the base for a men's pair. He asked Wilansky, with whom he had performed in Gymkana as students at Maryland, to be his top mount partner.

Wilansky is 5-7, weighs 126 pounts and has an undergraduate degree in microbiology. He had just been accepted to graduate school in neurology. After some thought, Wilansky turned against the wishes of his family, and deferred school to practice with Andersen.

"I knew it was the last time in my life that I'd be able to do something like this," he said.

At the time, there was also a possibility that acrobatics would be exhibited in the Olympics in 1988. "We had dreamed of Olympic glory," Andersen said.

So they began training about 12 hours a week, plus additional time spent in conditioning and dance classes. They worked around their full-time employment, often practicing as early as 6 a.m.

But the strain of this existence almost broke the two up before their first national competition. "When we can't get skills we tend to blame it on each other," Wilansky said.

That's when they began working with Ouellette, in part to help them with their technique, and in part to mediate disagreements.

Ouellette said acrobatics is like two-man bobsled. "They each have their own job, but they have to work together or they will accomplish absolutely nothing."

However, they stuck together and won the nationals in Honolulu with high enough scores to qualify for the World Cup competition in October.

Competitive routines are set to music, and in the balance and tempo sections cannot exceed 2 1/2 minutes each. The balance routine must contain five skills (stunts) together and three skills individually. They are judged on stability and strength, while the tempo portion requires five tossing and twisting moves and also tumbling and dance. Andersen formulates their routines, with assistance from Maryland dance professor Alvin Mayes.

In Baton Rouge, La., after the two days of preliminary routines in the World Cup, Andersen and Wilansky came into the final round in fifth place.

They were strong, but they still wobbled a bit and finished in fifth place in both balance and tempo. They were pleased with their performance in Baton Rouge, and were especially relieved that they literally held up under pressure, and didn't fall out of any skills.

The most important requirements in acrobatics, they agree, are flexibility and strength. The base has to be stable and have strong shoulders and legs. The top partner needs to be flexible and be of equal weight on the top and bottom. For that reason, neither one lifts weights, but they use "timers" -- simple repeated skills -- to keep them in shape and build strength. "At first I couldn't toss him high enough," said Andersen.

Acrobatics has only one piece of training equipment besides the mats -- a wedge-shaped block on a pedestal angled like a hand for practicing handstands. Andersen said tossing Wilansky above his head while Wilansky is doing a handstand was probably the hardest skill to perfect.

"The difficulty in basing is often unappreciated," said Wilansky. "The actuality is that it is just as difficult as being the top mount."

Neither one had any gymnastic experience before they entered the Maryland Gymkana troupe.

Andersen, though athletic in high school, did not plan on doing gymnastics in college. He said he was kicked out of high school in his senior year for missing class because he was smoking marijuana. He then went looking for a new life style.

Wilansky, into tennis and track in high school, was also determined in college to stop using drugs. Andersen said he then became involved in Gymkana, which stresses drug-free living.

"I looked for something to do {in college}," Andersen said, "and the fraternities were exactly what I was trying to get away from. Gymkana gave me a place where I could really apply myself and be in a group of people who did not do a lot of drugs and were interested in improving themselves physically."

Now both are out of school and Andersen coaches at the gym while Wilansky works at Division Medical fitting people for rehabilitative devices. Seeing people in wheelchairs, Wilansky said, brings home the risk involved in his sport "a little more than I'd like to think about." In learning new skills, he uses spotters and wears a safety belt attached to pulleys.

Since it is possible to compete in sports acrobatics into one's thirties, and partnerships take years to develop, they intend to compete several more years. "I think we have a lot in common because we're both real intense about what we get involved in," said Wilansky. "We couldn't have gotten this far without that."