star Lauren Conrad
(in Vitamin A) works with celebrity trainer Jarett Del Bene
to keep her body bikini-ready year-round. He keeps her on a high-intensity circuit training program just two or three times a week. "It includes full-body movements, boxing and lots of lunges, squats and step ups," says Del Bene. For a do-it-yourself circuit workout, combine a hike or run with breaks for lunges, squats and step-ups.