The upper back is often neglected when it comes to mobility training. Yet, most of us are stuck in thoracic flexion and could work on improving our upper back extension. This movement is one of our favorite movements to perform for working on thoracic extension.
Find a bench, couch, box, or other object that is a few feet tall. Kneel on your knees in front of the box, place your elbows on the box, and shoot your hips backwards toward your heels, extending through your upper back. You should feel a good stretch in your lats and triceps as well as feel some movement occurring in your upper back.
Play around with what feels good stretch duration and rep wise. Maybe it feels good to rep it out 10-15 times only holding the stretch for 1-2 seconds. Maybe it feels good to hang out for 20-30 seconds and do less reps. Listen to your body and give it what it wants.