You don't need to be standing in order to work your butt. Nope. You can tone, sculpt, and strengthen your backside on the floor. Here are 17 moves to try — pick three to five to add to your next workout, or try a few during your next TV binge. As for reps, start with 10 to 15 for each move and do two to three sets. If you don't feel up to creating your own workout, follow this 15-minute Pilates floor workout video that focuses on the derrière.