Kris Dorer used to play volleyball three or four nights a week. She did some power walking, too, and worked out at a gym.

Dorer played competitive sports all through high school in upstate New York and then after that recreationally, so she had grown accustomed to an active lifestyle by the time her daughter Shaelyn was born.

That was two and a half years ago. Soon after, Dorer’s exercising began to wane. When her second daughter, Meagan, was born nine months ago, the opportunities to work out – play volleyball, go to the gym, whatever – decreased even more.

“I was staying home and running them around to all kinds of activities, but I wasn’t getting in the workouts that I used to get before I had kids,” said Dorer, 40, an Old Orchard Beach resident.

Something had to give. In the middle of January, something did when Dorer became a Stroller Fit franchisee. In addition to looking for time to exercise, she had also been looking to start her own business. Stroller Fit was a perfect, well, fit.

“We actually use the stroller as a portable exercise machine,” she said. “We do different exercises with exercise bands and exercise tubes, using our own body weight for resistance. And we do cardio and strength exercises. The children stay in the stroller until we get out and do exercise on the mats, when we do our crunches and so forth. Then they come out and have a little playgroup while we finish our stretching.

“So the workout is for the adult, but we incorporate developmental activities for the children to keep them interested and having fun.”

So she could lead the classes herself, Dorer became a nationally-certified group fitness instructor and also got certified in post-natal specialized exercise by Stroller Fit. As of this week, she was offering nine indoor classes a week at locations in Scarborough, Saco, Cape Elizabeth, Westbrook, Portland and South Portland.

When the weather gets warmer, the classes will move outside to parks like Deering Oaks in Portland and Fort Williams in Cape Elizabeth, but there still will be auxiliary indoor sites for when it rains. There are a variety of membership packages available, ranging in cost from $15 for one class to $50 for an unlimited monthly pass.

“I have some people who have never exercised before in their lives, even before children, and I have people who are still runners and everybody in between,” said Dorer. “The most typical mom is someone who is fairly active prior to having children and now just doesn’t take the time because they’re putting their children first.

“This is a way that, not only can we get a good workout, but we can connect with other moms and spend time with our children. And the really good thing about the kids part is they’re seeing exercise is a normal, healthy, fun part of life. With the whole childhood obesity epidemic, that’s really important.”

Tuesday morning at Howard Indoor Sports in Saco, Dorer was expecting five or six moms with their kids, but only one – Missy Boisvert, 26, a Saco resident – showed up. These are parents with small children, so, as Dorer knows, obstacles sometimes come up.

“Kids get sick,” she said.

The class went on, though.

As Meagan sipped milk from a small cup, Dorer hit the play button on the boom box tucked into the back of the stroller so the moms could warm up. Boisvert’s daughter, 15-month-old Zoey, bopped back and forth to the music.

“She loves it,” said Boisvert, who joined up in January after getting a flyer in the mail. “She loves seeing the other kids, and she loves the social interaction especially at the end.

“I think it’s important for her and I to have the time, and it’s also important for me to make sure I’m healthy and active for her.”

And with Dorer running the show, Boisvert likely will stay healthy and active. After some light aerobic stretching, the moms pushed their strollers to the baseline of the basketball court and lined up for shuttle runs. Meagan, Shaelyn and Zoey sat back and smiled as Boisvert and Dorer ran them across the court.

“It’s not a fluffy workout,” said Dorer. “It’s actually a real workout, and we gear it toward the range of people who have maybe never exercised before to people who were very active prior to having children and who have been active.”

For more information visit www.strollerfit.com/Portlandme.