Muscles of the thoracic spine is arranged in layers and these muscles and ligaments work together to support the spine, hold it upright, and control movement during rest and activity. The layers of the muscles are superficial and deep. Appendicular muscles that are on the thoracic spine region are trapezius, rhomboid major and rhomboid minor. Muscles that are important in the superficial layer is the erector spinae muscle.  The Erector Spinae muscle actually consists of three columns of muscles, the Iliocostalis, Longissimus, and Spinalis, each running parallel on either outer side of the vertebra and extending from the lower back of the skull all the way down to the Pelvis.  The Erector Spinae provides resistance that assists in the control action of bending forward at the waist as well as acting as powerful extensors to promote the return of the back to the erect position. During full flexion (i.e., when touching fingertips to floor), the erector spinae muscles are relaxed and strain is borne entirely by ligaments of the back. Muscles of the erector spinae that are interacting with the thoracic region are spinalis thoracis,longissimus thoracis, illiocastalis thoracis, semispinalis cervicis, semispinalis thoracis and semispinalis capitis.

Erector spinae muscles of the thoracic spine