Sacro EXTENSION is a term used to describe the movement of the sacrum, or lower back, in relation to the iliac bone. The term is derived from the Latin word for 'sacrum' and the English word for 'EXTENSION, ' which refers to the act of extending or stretching. The iliac bone is located in the pelvis and is connected to the sacrum, making it an important part of the body's movement. Sacro EXTENSION is a type of exercise that helps to improve flexibility and range of motion in the lower back.