Thoracic Rotation

Lie on your side with your knees stacked and bent to 90 degrees, arms stretched out in front of you at shoulder height, palms together. Keeping your knees glued together and pressed toward the floor, open your top arm up and across your body, following it with your eyes and turning your chest toward the ceiling. Let your upper back rotate as far as it wants to go before your lower back or hips start twisting with it; the moment your knees lift apart, you've reached your real range and pulled the movement out of your lower back instead. Bring your arm back across to the start and repeat on the other side to compare how each side moves.