Whitney Pomeroy has an unusual routine.

But of the hundreds of people who know her by sight, few know much more about her than this.

What they know — what most anybody who lives in Belfast or passes through with any regularity knows — is that Pomeroy has been using the swing set behind Waterfall Arts every day, often several times a day, for years, swinging.

And not as other teenage girls might — a languid sideways motion as a backdrop to conversation with friends, the physical equivalent to drawing doodles during a phone call — but with a steady, focused rhythm.

The swing she chooses — always the same one — is a little too low, her 19-year-old’s legs canting to the sides on the backswing to miss the ground, her eyes straight ahead, occasionally turned down as she changes the song on her iPod.

Pomeroy’s passes are neither leisurely nor do they aspire to great heights, but she keeps it up for between one and two hours at a time. From a distance, the metal clunk of the chains shifting direction, coming just under two seconds apart, suggests the pendulum of a grandfather clock.

Pomeroy has been swinging more or less every day since she was 7, starting in Winterport where she lived until she was 14, using a swing at the elementary school, then at the swings behind Waterfall Arts when she moved to Belfast.

What lies behind this routine is complicated, but in short Pomeroy said it calms her down.

By her own account, she has had a hard life that includes a history of abuse, two suicide attempts and subsequent commitment to psychiatric facilities. She has also been diagnosed with Asperger’s Syndrome, a psychological condition related to autism, for which sufferers often seek activities structured around repetition.

A trip to the swings is often prompted by struggles at home — Pomeroy said she often argues with her mother, who has taken the view that her routine is a problem.

Pomeroy walks a mile from her home to use the swings in the heat of summer and below-freezing temperatures of winter, when her feet brush a swath of snow away beneath the seat of the swing. The walk is part of the routine, but the swinging itself is the goal, the repetition creating what she describes as a “comfort zone.”

When she is finished, she leaves that safe place, slowing the swing down and walking off without ceremony. The dismount is as automatic, distracted, as a commuter navigating the lip of the down escalator. Keeping some of the forward momentum, she glances down again at her iPod, making a straight path to High Street and home.

Like the endorphin rush experienced by the more common, but perhaps no less odd, activity of jogging, Pomeroy said the benefits of swinging last for some time after she leaves the swing set behind. But then nobody ridicules joggers.

“People say, ‘You swing every day, that’s weird.’ [I say] ‘What do you do to calm down?’”

Rhetorically, she answered the question: “Sex, smoking pot.”

“That’s kind of weird to me,” she said.

In other ways, Pomeroy lives the life of a typical 19-year-old.

She writes and plays guitar, the latter serving as the primary substitute for swinging in height of winter when she typically stops going to the swings. She listens to music: country, rock, metal, pop, though metal and alternative rock work especially well for swinging.

In school, she says, she did well in English and Creative Writing but had trouble focusing in other subjects. This she chalked up to the non-linear thought patterns of Asperger’s.

“Normal people can stay on one subject,” she said. But with Asperger’s, the subject at hand prompts other questions, and these prompt still more questions. The focus widens in concentric circles, each one further from the original problem. “You just go deeper and deeper. Then you’re thinking about the Big Bang,” she said.

From eighth through eleventh grade, she went to Belfast schools, then moved to Waldo, falling into the catchment area of Mount View High School in Thorndike. The high school adjoined the elementary school, which had a swing set for the younger students and on several occasions school administrators let Pomeroy use the swings when she was having an especially hard day, but mostly she was forbidden from using them out of the natural segregation of the schools.

During these years, she continued to use the swings in Belfast.

Pomeroy, who has since moved back to Belfast, said her home life has been tumultuous and she said having Asperger’s has made it difficult to make friends. Her trips to the swings have apparently not helped.

“People say, ‘Look, it’s the freak,’” Pomeroy said.

People she doesn’t know.

She counters: “I have a job. I’m going to college next year.”

Asked if anyone has approached her in a positive way about her swinging. Pomeroy didn’t need to reflect. As in the rest of her conversation, her demeanor kind and open, her answer concise, though a kind of fatigue showed in her eyes.

“No,” she said, matter-of-factly.

Not once?

Her head moved from side-to-side.

“No,” she said again.