Set-up: Start in the narrow-grip pushup position, with your hands together, a tight core and a neutral back.
Movement: Keeping straight arms, simply retract and protract the shoulder blades.
Emphasis: Keep the arms as straight as possible and do not allow the elbows to flex. Focus on the function of your shoulder blades - the range of motion is deliberately small. As in a traditional push-up, don't allow the hips or the lower back to sag.