Foam roller?

Great question. For thoracic extension, I'd go with a standard 36-inch roller so it stays stable under your spine, and medium firmness is the sweet spot for most people. A super firm roller can feel pretty aggressive on the spine, so if you're new to it, softer is safer until your back gets used to the movement. If you find your upper back is really tight and rounded, the Hunchback & Kyphosis Fix program walks you through exactly how to use the roller as part of a full routine.