HOW: Get set up ideally with your forearm supported on a surface with your hand off the edge. To begin the exercise make a fist with your palm facing up, then using your other hand try to push your palm down. However, don't let your hand/wrist move. Hold for the time prescribed.
FEEL: You should feel the muscles on the palm side of your wrist and forearm working with this exercise.
COMPENSATION: Do not let your wrist move, if it does you're pushing too hard