Summer is almost (finally!) here, which means you'll be slipping into a swimsuit in a matter of weeks. To help you tone up and feel confident in your two-piece, we bring to you our annual three-month Summer Shape-Up Program designed by Jillian Michaels. Here, you can watch the first workout in the series and break a serious sweat at home. Follow along as Kenta Seki, one of Jillian's master trainers, demonstrates the intense calorie-scorching and muscle-toning routine. For a text version of the workout, pick up a copy of the April issue of Shape magazine, on sale now.