Hilary Duff  Haylie Duff pilates blonde ponytail spandex

Hilary Duff is determined to get her pre-baby body back ASAP!

The former Lizzie McGuire star, who gave birth to her first child on March 20, worked it out at a pilates class in LA with big sister Haylie. Her newborn son Luca must have stayed home with dad.

Mike Comrie's 24-year-old wifey recently Tweeted, "20 minutes on the elliptical [trainer] seems like an eternity!!! What the hell!"

Every little step counts!