To increase mobility in the joints of the thoracic spine into extension.
Place a foam roller (or alternatively a tightly rolled bath towel) onto the floor and lie supine onto the roller so that it is positioned horizontally under your back.
You should begin with the roller positioned roughly in the middle of the back. Arms should be extended and pointed towards the ceiling
Slowly and in a controlled manner lie flat, allowing your back to arch over the roller. In this position relax and lower your arms to the floor above your head. Now sit up and reposition the roller a little higher and repeat until all of the mid and upper back has been mobilised.
A more specific mobilisation can be achieved by creating a smaller pivot. A good alternative is to tape two tennis balls together and position them so that the spine sits in the groove between the two balls. A Swiss Exercise Ball can also be used to good effect.