The Liftoff exercise works your shoulders, back, abs, butt and hamstrings.

Stick your chest out for me, Katie. Really engage that belly as tight as you can. Now, I want you to float your leg down just a little bit for me and I now need to lift your arms and your leg up at the same time so that everything is hip high. So float your arms up for me as well as the leg. Keep your tummy super tight and then take it back down to the bottom. Give me a few reps of that. This exercise is fantastic, not only for developing balance but getting that tushy super strong, engaging the core all the way from the top of the tush to the middle of the back, and the best part is this part of the top. She's engaging all the muscles in the back which is so beautiful for defining a gorgeous back for tank tops and bathing suits.