Prone scapula retraction - Shoulder "T" with thumbs up

Lie on your stomach.
Take your arms out to the side.
Lengthen and align your body through your toes to the top of your head.
Maintain the width of your chest and back and turn your thumbs to point up.
Lift your arms up and feel your shoulder blades moving towards your spine.
In a controlled manner, lower your arms back to the floor and repeat.