Let's break that down!
Sterno = Sternum- aka chest plate
Cleido = Clavicle or clavicular- aka collar bones
Mastoid = having to do with the Mastoid process- aka the landmark on your temporal bone, behind your ear
SCM for short! The sternocliedomastoid is a neck muscle that is easily visible when you turn your head to look over one shoulder. You have two, one on each side of the front of your neck.
What does it do? Primarily the SCM acts in moving the head and cervical spine. The SCM moves the head during specific angles of side bending and rotation, and when both SCMs contract together they create extension of the head (turning your face to the ceiling) and accentuate the curvature in the vertebrae of your neck (cervical vertebrae). However, when the head is fixed or held still the SCM elevates the sternum and clavicle assisting in respiration. You might make your neck look like a lizard sometimes on purpose- this is flaring your SCMs with a fixed skull.
Let's look at where it attaches to better understand how it affects our #necksupport. Your SCMs have two heads that originate on each side of the top of the sternum and along the edge of your clavicles close to the sternum. From their origins they sweep on a diagonal line across your neck, without attaching to any vertebrae to insert behind your ear. So these puppies connect your shoulder girdle and rib cage to your head.
Forward head posture is a common problem in our desk-driven and text-fueled society. In forward head posture, the SCMs can't perform their movement responsibilities because our alignment is so out of whack. In this poor alignment the side bending and rotating, that the SCMs usually take care of, gets outsourced to other groups like our traps! Yikes! All of this reorganizing and compensating leads to compromised positions, stress and imbalance on the structures of our neck, spine and ribs that can lead to long term issues. Are you reading this on a screen? Where's your head? :) Just looking out for you! Stay tuned for more on neck anatomy and posture as well as information to understand your spine!
See you in the studio! -Shorty