'Rhomboids' is the buzz word for this class. The rhomboid's function is to pull your shoulder blade (and with it, your shoulder/arm) back and inwards toward the midline of your body, and in doing so bringing space and openness to your chest, lungs and heart. Activate these muscles (there are 2 each side) which may be very helpful to those of you with upper back stiffness, tightness and general lethargy.