transversospinales muscles, a group of muscles deep to the erector spinae that consist of the semispinalis, multifidus, and rotatores muscles. When these muscles contract bilaterally, they extend the vertebral column, an action similar to that of the erector spinae group. However, when muscles on only one side contract, they pull the spinous processes toward the transverse processes on that side, causing the trunk to turn or rotate in the opposite direction.
