- At Sternoclavicular and acromioclavicular joints
- Superior fibers: elevation of shoulder girdle
Middle Fibers: retraction fo the shoulder girdle
Inferior fibers: depression of the shoulder girdle and upward rotation of the glenoid fossa (or lateral rotation of inferior angle of the scapula)
- At atlanto-occipital joint
- superior fibers of both muscles: extension of the head
- unilaterally: abduct to same side and rotate head to opposite side