Dance Anatomy & Kinesiology

The Upper Extremity 387

Palpation: While sitting in a chair, lean your torso forward until it is about horizontal and gently place

the fingers of your left hand in your right lower armpit against the costal surface of the scapula while

your right arm is hanging straight down toward the floor. The subscapularis can be palpated contracting

when the arm is slowly internally rotated in this position.

Other Major Glenohumeral Muscles

The remaining group of muscles generally spans greater distances and connects the humerus to the

trunk (including the ribs, clavicle, sternum, scapula, spine, and pelvis). These muscles are important

for generating the large movements of the arm. In addition to the muscles described in this section,

the biceps brachii and the long head of the triceps brachii also cross the shoulder joint, but they will

be discussed later in this chapter in connection with the elbow.

Pectoralis Major

As its name suggests, the pectoralis major (pect, breast,

chest + major, larger) is a large superficial muscle

located on the chest, and its development can be readily

observed in the area of the upper chest (figure 7.14).

The lower border of the lateral pectoralis major forms

a muscular fold (anterior axillary fold) and most of the

front wall of the armpit. The pectoralis major runs from

the inner clavicle, sternum, and costal cartilages of the

upper six ribs laterally to attach via a flat tendon to the

intertubercular groove of the humerus. Near the distal

attachment, the muscle twists clockwise 180°, leaving

it twisted when in anatomical position but untwisted

when the arms are raised overhead. The muscle is fan

shaped and is often divided into a clavicular or upper and

a sternal or lower portion. The line of pull of the clavicular

portion is such that it can produce shoulder flexion and

aid with shoulder adduction. However, when the arm is

above shoulder height, the line of pull moves above the

axis of the shoulder joint and it can then produce the oppo-

site action of shoulder abduction (chapter 2, figure 2.9,

p. 44). In contrast, the proximal attachment of the sternal

portion is low enough that it tends to consistently produce

shoulder adduction (and shoulder extension if the arm is

in a starting position where it is raised to the front). All

portions of the pectoralis major tend to produce horizontal

adduction and assist with shoulder internal rotation. The

pectoralis major as a whole is particularly important in

Attachments and Primary Actions of Pectoralis Major

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

Pectoralis major

(pek-to-RA-lis MAY-jer)

Inner two-thirds of

anterior aspect of

clavicle

Sternum

Costal cartilage of ribs

1 or 2 to 6 or 7 near

sternum

Intertubercular groove

of humerus extending

down from tubercles

about 3 inches (7.6

centimeters)

Clavicular:

Shoulder flexion

Shoulder abduction above 90°

Assists with shoulder adduction (lower ranges)

Sternal:

Shoulder extension

Shoulder adduction

Both:

Shoulder horizontal adduction

Shoulder internal rotation

FIGURE 7.14 Anterior view of superficial shoulder mus-

cles: pectoralis major and deltoid (right shoulder).

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