HOW: Start in the push up position with your hands on the ground and your elbows straight under your shoulders. Your toes should be pushing into the ground. While keeping your back flat and knees straight, push your body back and forth using your shoulder muscles exclusively.
FEEL: You should feel the muscles in your core and shoulders working.
COMPENSATION: Keep your elbows straight. Keep your back flat and knees straight as you move your body with your shoulders. Don’t move your body just by moving your feet!