Thoracic spine movement in three dimensions (tri-plane movement) is critical for both upper and lower-body function. The body is a kinetic chain and limitations in one part means the whole thing is compromised.
The T-spine is the foundation for all shoulder and arm motion. Pressing, pulling, throwing, punching, serving, batting, swimming, climbing, etc. all demand a contribution from your T-spine. If yours doesn't move well then other joints may pay the price. Poor T-spine mobility may be the root cause of shoulder, neck, and back problems.
Modern living limits your T-spine mobility. Standard gym exercises may not do enough to keep it healthy and mobile. Luckily, a few minutes spent doing a few drills will improve your function.
Most people have no clue how important T-spine mobility is for all sorts of movements from bench press, overhead press, any type of rowing/pulling, the Olympic lifts, throwing, and even running. Nearly all real-life athletic movements call on all the joints, limbs, and tissues to generate and absorb force.
When all the links of the chain move well and do their share of the work then you tend to feel good and perform well. If however, a joint isn't moving well and isn't able to share the load then it's typical that the joints and tissues nearby get beat up. Here's an example:
Pressing weight overhead requires shoulder flexion plus spinal extension. Spinal extension should be spread throughout the spine, from the lumbar up through the thoracic and into the cervical spine.
It's common to see limited T-spine extension when pressing (left photo). If the T-spine can't extend enough and you still want to put that weight overhead then you'll "steal" extra extension from the lumbar spine, extra flexion from the shoulders, and you may flex the cervical spine to an excessive degree.
Any number of problems may occur. Low-back pain is common in the scenario on the left. The shoulders may not be happy under high loads in this position either.
In contrast, the photo on the right shows a smoothly curved, extended thoracic spine. The load is more evenly distributed through the spine. This position means less low-back and shoulder stress and it puts the shoulders in a stronger position.
Most athletic actions demand thoracic spine movement simultaneously in all planes. Several of the following drills combine movement in two or three planes.
It's important to address the sagittal (front/back) plane, frontal (side-to-side) plane, and transverse (rotation) plane. Don't crank too hard on any of these. If the stretch is too intense then you'll only tighten up more. If anything hurts then back off a little. Only move as far as you can in a pain-free range of motion.
The corner stretch creates T-spine extension. Head movement and hip movement creates additional mobility:
Downward dog and variants create T-spine extension while the arms are loaded. Useful for anyone who presses overhead:
Side flexion creates frontal plane movement. Rotated side flexion combines frontal and transverse plane movement:
The side-lying upper body rotation fixes the lower body and moves the upper body. Gravity assists with rotation:
Lying lower-body rotation has the upper body fixed while the lower body moves. Gravity assists with rotation:
Max Shank's thoracic bridge is also an excellent drill. If you're very limited in the T-spine it may be a bit too advanced, but if you move well then definitely try it out.
You'll see the quickest results if you'll take a few minutes throughout the day and do one or two of these drills. Between sets of any exercise is also a great time to perform a mobility drill. And you can do these drills before a workout or a game.
You may find that you're more limited in one capacity than another. You may want to spend extra time working on your more limited movements. If you encounter pain, back off. Don't grind into pain. If you're in severe, persistent pain then don't be a dummy. Go see a physician.