It's the splenius capitis.
sternocleidomastoid
A combination of muscles: semispinalis capitus splenius capitus splenius cervicis
Located in the neck (Around the Cervical Vertebrae levels of C1 [Atlas] to C3) Just above the splenius cervicis And it helps support the skull
trapezius, splenius muscles, and semispinalis muscles
2I have found that cervical traction is effective in eliminating splenius capitis pain and neck cracking.
Splenius Capitis: for Part A on page 155 of the Holes bio book
That would probably be the splenius capitus muscle which is a thin triangular muscle, i.e. shaped like a bandage.
The sternocleidomastoid pair and the splenius capitus pair act to rotate the head around the joint between the axis and the atlas.The sternocleidomastoid pair and the splenius capitus pair act to rotate the head around the joint between the axis and the atlas.
What are the antagonist of sternocleidomastiod muscle?
There are many more than two muscles in the neck that perform the action of rotation. Among the primary contributors are the sternocleidomastoid (SCM)-the visible muscle that runs from beneath your ear to the top of your sternum-and splenius cervicis at the base of the rear portion of the skull. Other muscles like your upper traps and levator scapulae also play a role, though not as significant.
semispinalis capitis splenius capitis longismuss capitis spinalis capitis trapezius