HOW: Anchor a band directly behind you at shoulder height. Have the band to the side of the hand you will grab it with. Let the band pull your arm back while you rotate your upper half and reach straight out with the opposite arm. One you are rotated as much as you can, punch the band forward in a quick, controlled, motion as you pull the free hand back causing a slight rotation to the opposite side. Perform this for the prescribed amount of reps.
FEEL: You should feel you pec and shoulder muscles working as you punch the band forwards. You should also feel your core muscles working as you rotate.
COMPENSATION: Keep your hips facing forwards, try to only rotate your upper body.