"Structural integration is grounded in two premises:
First that physical and personal well-being requires appropriate adaption to the field of gravity.
Second, that the primary organ of body structure is fascia.
SI works because fascia is:
Physically and functionally continuous.
Responsive to gravity.
Able to transmit locally registered information throughout the body.
Malleable due to its visco-elasticity.
By exploiting these key characteristics of fascia as an organ of structure and communication, the traditional multi-session SI protocol delivers an orderly and well-supported arrangement of body segments in 3-D space along the imaginary plumb line and facilitates progressive levels of movement integration."
Borrowed from Fascia: The Tensional Network of the Human Body
By: Robert Schleip, Carla Stecco, Mark Driscoll, and Peter A. Huijing