HOW: Start in the quadruped position on all fours. Keeping your core/stomach braced and tight, slowly lift one leg and straighten it behind you, squeezing your butt. While doing this, do not let anything move.
FEEL: You should feel your core, shoulders, and hips try to stabilize your body while you are kicking back.
COMPENSATION: Pretend there is a glass of water on your lower back. Do not let your back/hips move and do not spill the glass of water!