What is erector spinae activity?

Answer 1

The erector spinae is actually a group of three long postural muscles; iliocostalis, longissimus and spinalis. Their actions are pretty much the same. Iliocostalis is the most lateral of the group. Its origin is the thoracolumbar aponeurosis and ribs one through twelve. It inserts on the transverse processes of lumbar vertebrae one through three, all twelve ribs and the transverse processes of the lower cervical vertebrae. In other words, it begins on the lower vertebral column, arcs outward across the ribs where it has both origins and insertions, and arcs back inward at the lower neck. The long tendons of iliocostalis extend laterally beneath the scapula. It allows unilateral lateral flexion and bilateral extension of the spine. Longissimus, the middle muscle and (as its name suggests) longest of the group, originates on the thoracolumbar aponeurosis and the transverse processes of the thoracic vertebrae one through five. It inserts on ribs four through twelve and the transverse processes of the cervical vertebrae ending at the mastoid process. Longissimus is thick and along with iliocostalis it makes a visible mound along the spine. As mentioned earlier, this muscle's cross sectional area, its thickness, tells you that it is very powerful. Its actions are the same as iliocostalis, but unlike the rest of the group, it has action on the neck as well. Spinalis is the smallest and most medial of the group, lying within the lamina groove. Unlike the rest of the group whose origin is inferior to its insertion, it originates superiorly; at the ligamentum nuchae, the spinous process of cervical vertebra 7, and the spinous processes of the lower thoracic and upper lumbar vertebrae. It inserts at the spinous processes of cervical vertebrae two through seven and the spinous processes of the upper thoracic vertebrae.