Set-up: Facing a wall, place your elbows against it at shoulder width. Bring both hands together behind your head.
Movement: Gently extend forward and backward into your elbows, slowly increasing range of motion in your middle and upper back. Be sure to keep your lower back neutral to ensure the movement in the exercise comes from the middle portion and not the lower part of your back. Bracing through your core and exhaling can both help to keep the position of the lumbar spine fixed.
Benefits: This exercise is designed to help facilitate extension mobility in the thoracic spine. Do not approach it as traditional resistance exercise, and attempt to improve your range of motion gradually.
Instructions and effects for the Thoracic Extension Against a Wall exercise 
Movement in Sagittal Plane