As we get older and wiser, sadly our backsides can get saggier and saggier. Actress Jennifer Aniston feels the pressure just like the rest of us to keep her tush toned, according to Allure magazine. While yoga is her main source of exercise, to firm her rear end she does regular reps of step-ups. For step-ups, place one foot on a step or platform and push through the heel to lift your body up. To do the exercises especially effectively, take it slow and concentrate on the working leg. Feel the burn and head to a set of stairs or raised platform to achieve a great butt!