Sublime

Richardson et al. (1999) identified the lumbar multifidus and the TVA as the key stabilizers of the lumbar spine. Both muscles link in with the thoracolumbar fascia to provide what Richardson et al. refer to as “a natural, deep muscle corset to protect the back from injury.”

The TVA appears to be the key muscle of the inner unit. Richardson et al. (1999) found that in people without back pain, the TVA fired 30 milliseconds prior to shoulder movements and 110 milliseconds before leg movements. This corroborates the key role of the TVA in providing the stability necessary to perform movements of the appendicular skeleton

the vertebrae need to be stabilized by core musculature in advance of the arm movement. But optimum stability does not prevent all movement in the spine — instead it allows small movements under control. Thus, proper stability, including core stability, is about a finely nuanced control of movement, as opposed to rigid prevention of movement.

There are two important groups of muscles that contribute to stability of the lower back and pelvis. Collectively they have been called the inner unit (core) and the outer unit (myofascial sling systems). The inner unit consists of the transversus abdominis, multifidus, diaphragm, and muscles of the pelvic floor—also collectively known as the core,

Stabilizing the nonmoving parts reduces the variables the brain has to deal with in predicting the consequences of muscle contractions.

The spinal engine theory put forward by Serge Gracovetsky, PhD, is explained and illustrated in very accessible form in Erik Dalton’s book The Dynamic Body (Erik Dalton, The Dynamic Body, Freedom from Pain