HOW: Begin this exercise on your hands and knees with one leg elevated on a pad or a book to allow your non-elevated leg to work through a greater range. From here, allow the knee that is not elevated to drop down towards the floor and then bring it back up to match the height of the elevated knee.
FEEL: You should feel the muscles of your back working to control this small movement.
COMPENSATION: Avoid excessive rotation through your pelvis as you perform this movement. Perform the movement slowly and with good control.