The Sternocleidomastoid muscle is the big thick muscle in the neck and is easily seen at the front of the neck when rotating the head the other way. It allows the neck to bend forwards and sideways.


  • Anterior surface of the upper sternum
  • Inner part of the clavicle


  • Mastoid process (behind the ear)


  • Contraction on both sides: Flexes the neck
  • Contraction on one side only: Laterally flexes (side bends) to the same side and rotates to the other side



  • Accessory XI nerve

Daily uses

  • Looking at the floor
  • Looking over your shoulder
  • Holding the phone between your ear and shoulder

How can I stretch it?

Shoulder Girdle Muscles:


More Human Muscles: