Spinalis thoracis
Musculus spinalis thoracis · Trnový sval hrudníku
Muscles
Looks like
The chest part of the spinalis, running from the spines of the upper lumbar and lowest chest vertebrae to the spines of the upper chest vertebrae.
What it does
Straightens the chest part of the spine.
Keeping it well
Strengthened by back extension exercises; not a common source of symptoms.