I'm a big believer in the concept of improving thoracic mobility to improve all your other movements. If your t-spine is moving, your lumber will be more stable. It will promote shoulder stability/mobility. It will improve cervical function and will also influence breathing patterns.
Yet, how many of us really strive to drive thoracic mobility? If one sits for a living (desk jockey) bikes a lot, is in the car for any amount of time, or tries to do some computer work, chances are you do these activities for some significant time.
Now, lets add in some specific strength training. We all like to deadlift, squat, farmers walk and do single leg work. All of these are tremendous exercises and all are done with stiff thoracic spine. (and rightfully so).
So we have frequency from life, volume and intensity from our lifting, all trying to inhibit are ability to move well in the thoracic spine. Thanks Evan Osar for getting me to think about how I lift in relation to actually hindering my thoracic mobility.
Enter crawling exercises. Having a one year old that is crawling all over the house has let me see first hand how crawling forces thoracic mobility. Crawling for time or distance can have an immediate impact on the t-spine. It's a closed chain activity which the brain loves. I really like some of Mike Fitch's "Animal Flow" exercises. Paul Chek has some crawling variations on YouTube that are worth pursuing.
So, if your want to do one thing to add into your programs or daily activities to have a good bang for you buck, crawl around.