Dance Anatomy & Kinesiology

The Upper Extremity 381

Individual Muscles of the Shoulder Complex

Scapular Muscles

The scapular muscles are comprised of six muscles that connect the scapula with the axial skeleton

(skull, spine, and rib cage). These muscles work both to hold the scapula in place (stabilization) and to

generate the movements of the scapula previously described. The importance of these muscles is often

underestimated, but they play a vital role in functional movements involving the arms. For example, the

scapular elevators are essential for effective lifting movements, the scapular depressors for effectively

pushing downward, the scapular abductors for forward pushing movements, the scapular adductors

for pulling movements, the scapular upward rotators for elevating the arm overhead, and the scapular

downward rotators for forceful adduction of the arm.

The scapular muscles can be subdivided into those located anteriorly and posteriorly. The anterior

muscles are the subclavius, pectoralis minor, and serratus anterior. Due to its small size and negligible

contribution to scapular motions, the subclavius will not be further discussed. However, the latter two

muscles connect the scapula to the front of the rib cage and share the ability to pull the scapula ante-

riorly (scapular abduction). The posterior scapular muscles are the trapezius, rhomboids, and levator

scapulae. These muscles serve to connect the scapula to the spine and are all capable of pulling the

scapula posteriorly (scapular adduction). The individual scapular muscles also have other actions that

are described next and summarized in table 7.1 on page 384.

Attachments and Primary Actions of Trapezius

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Trapezius

(trah-PEE-zee-us)

Base of skull

Ligament of neck

C7-T12 spinous

processes

Outer third of clavicle

Upper acromion

Upper spine of scapula

Upper: Scapular elevation

Scapular upward rotation

Scapular adduction

Middle: Scapular adduction

Lower: Scapular depression

Scapular upward rotation

Scapular adduction

Trapezius

The trapezius (trapezion, irregular four-sided figure) is a

superficial paired muscle located on the back of the neck

and upper back on each side of the midline (figure 7.8). The

paired relatively flat muscles derive their name from the fact

that together they form a diamond shape, or trapezium. Due to

its shape the trapezius is also sometimes called the “shawl”

muscle (Smith, Weiss, and Lehmkuhl, 1996). Because of the

different line of pull and innervation of different portions of

the trapezius, it can be divided into three parts—the upper,

middle, and lower trapezius. To visualize the actions, it is

helpful to mentally construct the line of pull of these three

portions. The upper portion courses downward and laterally;

the middle portion is more horizontal; and the lower portion

courses upward and outward. As a whole the trapezius tends

to produce upward rotation and adduction of the scapula.

To understand how the trapezius could produce upward

rotation, it is important to note that it attaches onto the upper

FIGURE 7.8 Superficial posterior scapular mus-

cles: trapezius (left scapula).

http://www.ebook3000.com