Kari H, thank you for your message and question! Upward rotation of the shoulder blade is what happens whenever you lift your arm overhead. It’s the rhythm of your shoulder blade and upper arm bone( the humerus) in relationship to each other to lift the arm. Looking at the triangle shaped shoulder blade on your back, the outer border away from the spine, moves out and up. The inner border close to the spine, goes down and out. This creates an upward rotation as you lift the arm over. This allows you to lift the arm and keep the arm aligned with shoulder joint and have dynamic stability! All the best!🙏