With centralization, the painful symptoms move from a place below the spine up to the midline of the low back area. This change occurs when the patient is placed in an extended position or moves the spine into extension.
Lying on your stomach in the prone position is one starting point. The patient uses the arms to press the upper body up off the table. This is a prone extension position or exercise. If the buttock or leg pain moves into the lower back area, centralization has occurred.
Extension can also be done in the standing position with the same results. In fact, both of these test positions are also used in the treatment of LBP when centralization occurs.