The other women in class curled dumbbells as they lunged. But Lindsay Macaleer put down her weights and instead gently rocked her double stroller to soothe her 2-year-old and 10-week-old sons.

"I just want them to be quiet, so I'm modifying my workout," whispered the Arlington, Virginia, resident, who was grateful to be back into her exercise routine at all. For Macaleer, 34, that's three days a week taking either a Stroller Strides class, which combines high-intensity aerobics and strength-building moves, or Stroller Barre, which borrows sculpting techniques from ballet and Pilates.

Both offerings are available through Fit4Mom, which was known as Stroller Strides until this summer. The 12-year-old program, founded in San Diego, California and now at 275 franchises across the country, has gradually expanded to incorporate prenatal fitness, classes for moms without their kids in tow and moms' social clubs focused on nights out rather than working out.