Amid summer vacation indulgences, falling off the workout wagon is understandable. Get your body (and your bum!) back in shape with tips from actress Jessica Biel who got into even more bootylicious shape as she trained for her role in Total Recall. Fitness expert Brad Martin tells Self.com the trick to toning your rear is in a move called "The Ass-inator." Start with left foot slightly in front of right, arms at chin level, elbows bent and hands in fists facing each other. Push off right foot, rising up on left tiptoes and driving right knee up and across body toward left, while rotating to the right. Do this move 15 times per set, and three sets to get a Biel-worthy booty.