It’s one of those Why Didn’t I Think About It Before ideas.

One: Moms use strollers to bring their babies here and there.

Two: Pushing a stroller can be a little bit of workout.

Three: Running  with a stroller can be a great workout.

Four: What mom has time to work out?

Hmm. Add a professional trainer, and what you have is Stroller Fit, a program that doesn’t just let moms bring their babies to the gym, but uses the carriages, and the weight of the babies, to help mothers get in shape.

Stroller Fit is a national franchise; so far the only New Jersey representative is Stephanie Worthington, who runs her classes out of the PAL in Parsippany.

“Every exercise incorporates the kids, whether it’s moving, singing, lifting,” Worthington says. A typical one-hour session includes cardio, strength, flexibility and core work.

For instance, the women run with a stroller half way to the middle of the gym, leave it there and sprint back to where they started, turn right around and make a dash back to the stroller, then run it to the far end of the gym. Repeat.

Or they’ll do “Peek-a-Boo Squats,” as mom stands in front of the stroller, hiding then showing herself to baby while bending her legs at the knees and hips to work out the lower body - and keep baby cooing.

“Moms bring their babies, so they don’t have to worry about a babysitter,” Worthington says. Another advantage, she adds, is that the toddlers in the class actually learn to exercise along with their mothers.

It’s never too early to start getting in shape!