Erector Spinae: A group of muscles and tendons which run nearly the entire length of the spine, helping to extend it and maintain upright posture.
Semispinalis Capitis: A muscle located deep in the back of the neck that extends from the upper thoracic vertebrae to the base of the skull, aiding in head extension and rotation.
Splenius Capitis: A broad, strap-like muscle in the back of the neck that assists in movements such as rotating, bending, and extending the head and neck