Published: July 21, 2008 12:00AM

It’s 9:30 a.m. on a Friday, and Liz Amen and her 14-month-old daughter, Katie, are getting a killer workout.

Well, at least one of them is.

Amen steps on and off the raised planters at Alton-Baker Park, keeping a close eye on her toddler, who sits contentedly in a line of strollers filled with a dozen other babies and tots.

While the moms (and one dad) bob up and down, working up a sweat, the little ones munch on raisins and suck on sippy cups. A few of them look like they could easily go for a nap right about now.

For many new moms looking to lose a few extra pounds of baby weight and not have to pay for a baby sitter and a gym membership, working out in a group with a jogging stroller and a baby (or two) is a winning combination. It’s called Baby Boot Camp, and moms say the results speak for themselves.

“I gained 56 pounds during pregnancy,” Amen says. “Not only did I lose the weight, but I lost 15 more pounds. ... Honestly, I was not a physically active person when I had (my baby). Now, I love to get out and be active.”

Amen says she still complains when her Baby Boot Camp instructor, Meredith Mills, makes her do an...