Closed chain mobility is fixing the distal body segments such as the hands and feet and moving the proximal segments such as the pelvis and scapulae around the fixed extremities. This method of mobility allows for increased awareness of your body's tendency to compensate around limitations, while also building awareness of the musculature that needs to be active in order to better stabilize your position.

This video is a tutorial of "Banded Shoulder Extension", in order to improve mobility and positional awareness as the shoulders are held in extension.