MILTON — When Nichole “Nikki” Bieber came into Heart Line Health and Fitness on a recent rainy afternoon, her arrival was heralded first by the appearance of her son AJ. Then in came daughter Avery. And finally Bieber herself arrived, carrying a large case of bottled water in one hand, a bag with her workout clothes in the other, and using her elbow to hold the door open for her other daughter, Amara.

She looks like the typical harried mom, that is until you notice her well-defined biceps.

Bieber became involved in body-building a year ago, and at her most recent competition on June 1 in Plattsburgh, N.Y., she took first place in the pro-am category.

That was quite an accomplishment, since she received her pro card in mid-May at the New York State nationals event in Binghamton only a couple of weeks before.

While the trophies and the applause she receives at shows are gratifying, they aren’t the most important thing to her.

“My biggest reward is what my kids are learning about eating in a healthy way and the importance of physical fitness,” she said.

A ‘Wonder Woman’

Her son AJ, 5, thinks she’s Wonder Woman, she laughs, and 2-year old Amara loves to come to gym with her while she works out.

“I got her her own 1- and 2-pound dumbells, and she exercises right along with me,” she said.

Bieber, 32, is a chiropractor and part owner, along with her husband Andrew, also a chiropractor, of Heart Line.

She got started teaching group fitness classes at Heart Line five years ago to get back in shape following the birth of her son, she said.

“At the time, I couldn’t afford a gym membership, so I started teaching to get a free membership,” she said. As part of her workout, she did some weight lifting, and other lifters encouraged her to compete. Since she started lifting, she developed a rigorous schedule to give her time for workouts, as well as a strict diet.

Work and workouts

She rises at 4:15 a.m. and pops an egg-white omelet in the microwave in her Turbotville home, and by 5:30, she’s unlocking the doors at the gym. She works out for a couple of hours, then heads for her office in Millville.

Meanwhile, her husband is getting the three children up and out the door.