Dr. Stuart McGill changed the game with his outlook on core training to save the spine. He provides a great blueprint on bracing the core and all of the muscles that help stabilize your spine from just about every direction, which can improve performance.
The "stir the pot" exercise is great for learning to brace the core:
Now let's ramp it up a notch. Try this variation:
- Grab a suspension gadget (TRX, rings, Blast Straps, etc.) with your body in the plank position – body straight from neck to toes and core braced tight.
- Make half circles with your forearms/elbows so the suspension device goes around your head, from shoulder to shoulder. Try not to move your body. (You can't complete the circle because your head will be in the way, obviously.)
This exercise is tougher than it looks. You'll feel it all over your body. As you get accustomed to it, focus on limiting the speed of the movement and making larger circles with more tension throughout the body.
This advanced exercise will improve your strength and stability, and it'll have a big impact on your shoulders and back.