Get your baby and do a lap,” shouted the instructor, sounding more like a drill sergeant than the mother of a toddler.

Dutifully, each mother firmly grasped the handles of her stroller and jogged around the gym at the YWCA of Bangor-Brewer. As the panting women pushed their children around the highly polished floor, the babies sat nestled in the fabric sling of umbrella strollers. One laughed, another squirmed, while a couple of them napped as the walls whirled past them.

“I wanna get out,” whined one boy as he arched his back and twisted around so his mother could see his face and know that he meant business.

In a moment, he was whisked into a circle at the center of the gym. His mother jogged backward, away from his outstretched pleading arms.

“Walk on your hand and toes to your baby then give him a kiss,” ordered the mother in charge.

Like toddlers trying to stand up alone, the women inched toward their children. Red-faced and sweating, each mother bussed her baby’s cheek before backing up again. One child giggled, another clutched his mom’s hair in a thwarted hug, another fussed and wiggled, while a third dozed off, unaware of the activity surrounding him.

This is Cardio Baby, an exercise class led by Sarah Fraipont, 34, and her 21-month-old son, Ford. For 45 minutes twice a week, the two lead seven other mothers and sons in an exercise program that “is not for the weak,” according to the instructor.

“It’s not your typical exercise class,” said Fraipont, who teaches classes part time at the YWCA. “We start off with laps at the beginning, then do some interval training with the kids in the strollers. The last 15 minutes or so, we let them get out to run around while the moms do push-ups and sit-ups.

“We do a big variety of exercises that are low- and high-impact aerobics,” she said. “It’s pretty different every time. I try to gauge how the parents and babies are doing. If one child starts to fuss, we’ll do another lap, or if they’re trying to climb out of the strollers, I let them out early. I have to go with the flow.”

The YWCA offered the class for the first time in September. Fraipont, who taught similar classes when she lived in the Carolinas, suggested the Bangor facility put it on the schedule. Enrollment increased to seven participants the second session, and registration starts today for the next, which will begin Dec. 31.

Fraipont said that the only requirements are that parents use umbrella strollers and that children be between the ages of 8 weeks and 3 years. All of the babies enrolled in the current session are boys between the ages of 13 months and 2 years.

“The class offers a mother a way to be with her baby, not have to pay a baby sitter, and get a workout,” said Fraipont. “It’s a great way to get right back out there [after the birth of a child], meet other mothers, and get back into shape.”

She added that exercising with a child early most likely would mean he or she would grow up to be a healthier and fitter adult than the average sedentary American.

“If you start exercising with a baby, the child will grow up seeing that exercise is the norm,” pointed out Fraipont.

Stacey Benge of Hermon said that the class turned out to be very different from what she’d expected, but she plans to take it again.

“I thought it would be easy,” said the 31-year-old mother of two who brings her 22-month-old son, Alex, to class. “It’s harder than some STEP aerobic classes I’ve taken, but I enjoy the challenge and want to get back in shape for myself. Alex enjoys the excitement and the activity of it, especially getting out of the stroller, then running around.”

Mothers bring juice or milk and snacks for the children since the class is held close to lunchtime, from 11 to 11:45 a.m. Mondays and Wednesdays. Toward the end of class, while their mothers were still working out, the boys imitated them by pushing the strollers around the room themselves or trying to do push-ups. They even kicked a soccer ball around the gym for a few minutes before running back to check on their mothers’ progress. A couple offered encouragement with a few pats of the mothers’ heads or shoulders.

“I signed up for this class for fitness and to lose weight,” said Benge. “I like that I can include my child in that so that when he grows up, he’ll always enjoy exercising.”

Kathy Rice, 41, of Bangor, and 2-year-old Matthew take the class while his 4-year-old sister is upstairs at the Y’s preschool program. Matthew is the oldest boy in Cardio Baby and the only one who has never dozed off during class, according to his mother, who’s already signed them up for the next session.

“He’s never slept, because he just loves to watch me suffer,” joked Rice. “At home, he does push-ups. It’s a good workout, real intense. I’d never do it at that level on my own. I wouldn’t run around in the driveway pushing a stroller like that.”

For information on the Cardio Baby Class, call the YWCA at 941-2808.