Just about every time Julie Zetlin has traveled with the hoop that’s an essential part of her sport, she has tangled with airline officials, felt the stares of fellow passengers and fielded outlandish questions.

Is that a Hula Hoop?

Is that something you wear under a dress?

Are you part of Ringling Brothers?

To flight attendants, Zetlin replies, “Yes, it is permissible carry-on luggage.”

To everyone else, she explains, “No, I’m not in the circus!”

A Bethesda native, Zetlin is the first U.S. rhythmic gymnast to qualify for the Olympics since 2004, as well as a former student at Walt Whitman High School and die-hard Washington Capitals fan.

She heads to London later this month with no expectation of winning a medal in a sport dominated by Russians. Instead, her goals are to stage a fearless, mistake-free performance; raise awareness of the sport she loves; and, ideally, inspire the next generation of Americans to surpass her and one day win Olympic gold.

She takes no less pride in that.

“I think I’m upping the game for U.S. rhythmic gymnastics,” says Zetlin, 22, whose mother was a junior national champion in Bulgaria. “We’ve been stuck at a certain level for a while, and I think I’m kind of the one that’s crossing the boundary line. I’m just trying to improve my sport and help improve our girls — make them want to work harder and work longer. Too many quit too early and don’t get anywhere.”

Rhythmic gymnasts tend to peak later than traditional gymnasts because their sport is rooted more deeply in ballet and performance. They also tend to be taller, given the premium placed on creating fluid, evocative lines with four pieces of equipment — a ball, hoop, ribbon and baton-like clubs — that alternately soar through the air and serve as extensions of their bodies in choreographed routines set to music.

In Zetlin’s case, qualifying for the Olympics represents nearly two decades of work and persistence through two knee surgeries.

“My mom founded a rhythmic team and enrolled me, and I loved it because I loved to dance. I especially loved to dance around with the ribbon,” Zetlin recalls. “I was very hyperactive as a little girl, so it was definitely my calling.”

Her ability blossomed as she grew taller — she’s now 5 feet 6 ½ — and honed her skill in classical ballet.

“I’m the type of gymnast who really loves performing to different types of music and letting my personality shine on the carpet,” Zetlin says. “That’s one of the most fun things about rhythmic gymnastics for me: To show that I’m an actress as well.”

Rhythmic gymnasts need a combination of extreme athleticism, artistry, flexibility and hand-eye coordination to perform their routines with the sport’s four apparatus.

The ball routines showcase gymnasts’ flexibility. Like a must-see-to-believe performer in Cirque de Soleil, Zetlin makes the ball travel up and down her limbs during dance sequences and tosses it in the air, catching it in a crook in her leg or the nape of her neck, in the midst of dynamic tumbling passes.

Ribbon routines showcase spins, with gymnasts performing on the balls of their feet, known as demi pointe in ballet.

Routines with the clubs demand balance. And the hoop incorporates all of these elements.

With each, Zetlin attempts to tell a story through music, costume, choreography and gymnastics.

Says Olga Kutuzova, the Russian coach who has worked with Zetlin since she was 9: “You definitely need to be mature to compete. It’s not enough to just be flexible or to just toss and catch the ball. People are watching you, and you must perform your exercise — not just do exercises. You are doing a story on the floor.”

Unlike many world-class athletes in traditional American sports, Zetlin gets no funding from the U.S. Olympic Committee. She gets modest financial help from USA Gymnastics, but her pursuit has been expensive, with her Swarovski crystal-encrusted custom leotards costing $1,500 each.

It has also been a bit lonesome, marked by years of four- and five-hour daily practices in a school gym in Darnestown, Md.

“Home of Julie Zetlin, 2012 Olympian” reads the banner that was hung this spring.

A recent practice began as all do, with an hour of stretching and preparation to practice. On this day, the U.S. National Team’s ballet instructor, Sonya Yankova, is also on hand and snaps her fingers to set a tempo as Zetlin, dressed in snug navy shorts and shirt, goes through ballet positions.

“Arabesque. Plie,” says the Bulgarian native, who offers gentle advice and encouragement in a hybrid Russian/English. “Push the heels in! Go! Go! Go! Long arms! Balance! Shoulders! Smile! Brava!”

Asked during a break what she considers Zetlin’s strength, Yankova cites her natural jumping ability and keen mind. “She is very smart,” Yankova adds. “Intelligent. Open. Very honest. This is our treasure: Julie’s talent.”

When it’s time to practice with the apparatus, Kutuzova cues the music for the first 90-second routine, and Zetlin gets her green ball. The coach suggests she omit the jumps; the gym’s carpeted floor is less forgiving than the cushioned Olympic surface, and there’s no sense in aggravating Zetlin’s surgically repaired knee.

Zetlin runs through the routine once, then repeats short sequences that Kutuzova feels need polishing.

Zetlin never balks or complains but keeps working even as her father, who owns a Mercedes dealership in Arlington, pops in for a surprise visit with a camera around his neck.

It is painstaking work, striving for perfection. But after 18 years or practice, the eve of the Olympics is no time to cut corners.

“My body every day tells me more and more that time is limited,” says Zetlin, who plans to retire after London. “The goal and the dream was to make the Olympics. This is it. This is my time. This is my prime. I’ve done what I needed to do — not just for me but for USA gymnastics.”