HOW: Start by assuming the tall plank position with both hands on the ball. Then slowly slide one hand into the middle of the swissball and gentle take away your other hand. Really drive the palm of your hands into the swissball in an attempt to drive it into the ground. Push your body as far away from the swissball as possible
FEEL: You should feel all the muscles in your shoulders and chest working to stabilize the position, especially the muscles in your armpit region.
COMPENSATION: Try to keep your shoulders squared up and both equally facing the group. It may be easier for you to spread your feet apart to give you more stability.