HOW: Start on your hands and your feet, have your hands positioned under your shoulders. Both hands should be in line with one another. To begin the exercise, assume a high plank position, while keeping your body straight lower your chest down towards the ground as far as you can as you shift your weight to the other hand. Then shift your weight back to the other side as you up to the starting position and repeat.
FEEL: This should feel like an upper body workout, your shoulders, chest, and triceps. You should also feel your core and your glutes/quads working to maintain a straight body from your heels to the back of your head.
COMPENSATION: Keep your body in a straight line, don't hike your hips high in the air or let your butt sag to the ground.