Two mixed-doubles teams dashed around a badminton court at the Thomas Jefferson Community Center in Arlington — but they were not playing badminton.

Instead, it looked as if the players were using oversize table-tennis paddles to volley a whiffle ball over a slightly undersized tennis net.

Don’t recognize the game? It’s pickleball — a tennis-badminton-table-tennis hybrid invented half a century ago by a congressman and a couple of his friends to keep their kids occupied. Today the game, with a smaller court than tennis and a slower, lighter ball than other sports, is finding a growing audience, particularly among seniors.

“It’s easy to learn, good to enjoy, and you get a workout,” said Desiree Fey, 66, an economic assistant at the Labor Department. “Just look at me.” The 66-year-old’s hot-pink bandana was doing little to sop up the sweat.

“It’s the fastest-growing sport in the country,” claimed Jim Joyner, chairman of the Arlington County Pickleball Committee, which promotes the sport and arranges regional tournaments. Joyner didn’t have any hard evidence to back up his statement, but the USA Pickleball Association says its membership of more than 2,800 is five times what it was only four years ago.

For at least 15 years, TJ, as the center is known, has had two pickleball courts available to its members. Three years ago, TJ started offering lessons for adults 55 and older. Around that same time, Walter Reed Community Center, also in Arlington County, began hosting pickleball games and lessons for all ages.

This summer, the county’s parks department is painting pickleball lines on the two tennis courts in Jennie Dean Park, creating the area’s first public outdoor pickleball courts. Local players had lobbied for them for years, since national tournament games are played outside in Buckeye, Ariz. (This year they will be held Nov. 6-14.)

“Pickleball is growing so much in popularity,” said Eric Legg, sports programmer for the parks department. Legg said the repetitive “pick-pluck-plunk” sound of the bouncing pickleball — a little louder and more irritating than the sound of tennis balls — was a concern in siting the outdoor courts. The department settled on Jennie Dean Park because it is not near any residences and is not often used by tennis players.

Named after Pickles, a ball-snatching cocker spaniel, pickleball was invented in the summer of 1965 by Joel Pritchard, a future Republican congressman from Washington state, and his friends William Bell and Barney McCallum. The friends wanted to play a game everyone — girls, boys, adults, seniors — could enjoy. From Pritchard’s back yard, the game slowly expanded; in 1976, Tennis magazine called pickleball “America’s newest racket sport.” The national association was founded in 1984, the same year the first rule book was published.

The rules are simple. Played on a badminton-size court, the game begins with an underhand serve from behind the baseline. The ball must sail over the 34-inch-high net and bounce into the opponent’s service box.

Once the opponent returns the serve, the ball must bounce back into the server’s court. Only after this “double bounce” are players allowed to volley (return the ball without a bounce), ramping up the speed and intensity. No volleying is permitted within seven feet of the net. Points can be scored only by the serving team. Play goes to 11 points, and a team must win by two points.

Del Webb, a major developer of communities for people 55 and older, has been modifying tennis and basketball courts for pickleball for the past five years. More than half of the more than 50 Del Webb communities now offer pickleball.

Although mostly marketed to seniors, pickleball is also being played in physical education classes at middle schools and high schools, including some in Arlington and Fairfax counties.

“In pickleball, anybody of either sex at any age can play,” 75-year-old Joyner added. “It’s a fun game.”