The Washington area has experienced remarkable growth in construction of handball-racquetball courts in the last four years.

In early 1973 there were 12 of the four-wall indoor courts. Today there are more than 105, and at least 75 more are under construction or planned.

It all started in October, 1973, when the area's trial balloon of the court clubs - Courts Royal at Merrifield -opened with four handball-racquetball and two squash courts.

Partners Walter Cuenin and Robert Bohn followed up two months later with Courts Royal East in ALexandria, with six handball-racquetball courts.

By May of last year, when Courts Royal East expanded to eight courts, others facilities were springing up at court clubsM apartment-condominium high-rises, parks, military installations and colleges.

While most other wall-to-wall sports require skills that take frustrating months to develop, racquetball say only a few hours of instruction are needed to play an acceptabble game.

Racquetball's biggest rival is its older brother, handball. The two are played on the same 20-by-40-by-20-foot court with almost identical rules, but many handball players view racquetball as a "sissy" sport.

Easewhere in the United States handballers are still so dominant that racquetball remains suppressed at some YMCAs and other court facilities. But in the Washington area a truce seems to have been reaches.

Here handballers seem to recognize that the more durable walls of the new courts and the plastic bumpers that have been added to racquets result in little damage and few smudges to the walls.

Racquetball, invented in the late 1940s by a Connecticut tennis pro, remained practically unknown until about five or six years ago. The sport claimed only about 50,000 players in 1970.

Since then, nearly 600 court clubs have been buit in the United States and participation is growing by such quantum leaps that it is difficult to estimate the number of players. A survey by the A.C. Nielsen Co. in February-March, 1976, showed an estimated 2.7 million racquetball and 5.3 million handball players in the nation.

Racquetball wasn't defined in the Random House (1966) or American Heritage (1970) dictionaries. It wasn't mentioned in James A. Michener's opus last year, Sports in America, or in the first 20 printings of Dr. Kenneth H. Cooper's The New Aerobics. But Cooper's latest book on aerobics is to be published Nov. 24, and in a telephone interview from his Dallas office he said that it will recommend identical standards for handball and racquetball - a minimum of four hours perweek, not counting breaks or time outs.

Playing one hour of singles in either sport give you nine aerobic points, and one needs at least 34 to 36 points per week, Cooper said. "Playing doubles cuts that value way down," he added.

Dr. Marcus B. Sorenson, director of the National Institute of Fitness, a vacation and weight-reducing operation in Orem, Utah, maintains that "racquetball is far superior to any other sport we have tried in our program of weight loss."

In a National Racquetball magazine article he wrote that for an activity to be of lasting value in weight control it must produce enjoyment for consistent participation, require a very low level of skill in the beginning to prevent discouragement, and must not become boring.

"Racquetball is the only sport which has all of the listed attributes," he said.

Racquetball has also opened the door to wall sports for a big chunk of the American populace.

"This is the first time in history that handball courts have been open to women," said Cuenin, who estimates that females make up 40 per cent of the racquetball players at the Courts Royal clubs in Northern Virginia and Richmond.

"We cater to women - nursery, women's days, women's ladder, tournaments," he said. "We offer women everything we offer the men."

Television coverage of racquetball seems just around the corner. Last spring the World Racquets Championship on CBS featured top racquetball players competing with the best in tennis, squash, badminton and table tennis.

Earlier this year the International Management Group in Cleveland, agent for such stars as Ilie Nastase, Bjorn Borg, Yvonne Goolagong and Arnold palmer and for 100 of the 130 hours fo television tennis in 1976, entered into a contract to put racquetball on the tube.

The U.S. handball and racquetball associations, both headed by Robert W. Kendler, are setting up state associations. Kendler, who developed glassback walls, now has in mind an allglass court to facilitate TV coverage, a softer handball to open that game up to women and youngsters, expandable modules to put the two sports within the reach of the poorest communities, and expansion in Europe.Several sporting goods manufacturers, among them Saranac, Spalding, Leach, Seamco, Ektelon and Patrick, seem to be stepping up their promotional activities, such as sponsoring pro tours and providing free balls for juniors tournaments. Voit sponsored the Capital Classic racquetball tournament at Courts Royal East last month and Adidas reportedly is coming out this fall with a complete line of racquetball shirts and shorts.