HOW: Begin on your hands and knees. In this position, you will balance on the opposite arm and leg. The more narrow your setup is, the easier this will be, just focus on the weight shift noted in the video. Keep your back flat and your core engaged. Bring one arm and the leg on the same side up until your leg is straight out from your hip and your arm is straight out from your shoulder. Alternate doing this on both sides for the prescribed amount of reps.
FEEL: With the leg kicking out you will feel the muscles on the back of the hip working, with the arm that is punching out you will feel the muscles on top of the shoulder and back of the shoulder blade working. You should feel your core muscles working the entire time as this is a challenging balance exercise!
COMPENSATION: Avoid rotating the trunk, arching the back as you raise your leg, or shrugging the shoulder as you raise the arm.