Other Muscles: More Detail: The Shoulder Girdle: Function & Issues

[The serratus anterior is] always well-developed on superheroes. – Andrew Biel, Trail Guide to the Body 2010 p 86

Broad, thin muscle covering the lateral ribcage
It originates at the first eight or nine ribs and runs to the medial (inner) side of the scapula
Referring to its location, it may be called the “bear hug” muscle
Most of the serratus anterior is deep but the portion below the armpit is superficial
Helps hold shoulder blades against rib cage
Helps to move shoulder blades away from each other (protraction)
Used in push-up
Supports upper back, shoulder and chest in Plank, Chaturanga Dandasana and many arm balances and inversions
Helps in bringing arms overhead as in Virabhadrasana I
Antagonist to the rhomboids
See more on these muscles in Anatomy of the Shoulders: Functions & Issues

Rhomboid major originates from T3 to T5 and inserts on lower border of scapula
Rhomboid minor originates from C7 to T1 and inserts on upper third of scapula
Adduct the scapula
The upper rhomboids “are particularly strained by their effort to pull the shoulder blades back into place” when the pec minor is tight and/or shoulders are chronically rounded (Doug Keller)
Tension in these muscles can cause chronic pain along edges of shoulder blades nearest spine

Originates from C1 to C4
Elevates and rotates shoulder blades downward
Laterally flexes the neck
Works with trapezius to shrug shoulders upward
These muscles can be strained when there is rounding of the shoulders
Tension in these muscles can create pain in the sides of the neck and make it difficult to turn the head (Doug Keller)