HOW: Begin on your hands and knees. In this position, you will balance on the opposite arm and leg. The wider you are the easier to balance, the more narrow the more challenging this will be. Keep your back flat and your core engaged. Bring one arm and the opposite leg up until your leg is straight out from your hip and your arm is straight out from your shoulder. Once in this position, pulse your arms and legs up and down at the same time for the time prescribed. Then alternate doing this on the other sides.
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.
COMPENSATION: Avoid rotating the trunk, arching the back as you raise your leg, or shrugging the shoulder as you raise the arm.