The Upper Extremity 407Shoulder External Rotation
When the hand is free to move, shoulder external
rotation refers to rotating the humerus outward
along its long axis in an approximately horizontal
plane as when one rotates the arm outward from
anatomical position so that the point of the elbow
(olecranon process) faces into the side of the body. In
strengthening exercises, this movement is often per-
formed against external resistance with the elbows
in a flexed position, as in the kneeling scarecrow
(table 7.10H, p. 439) and double-shoulder external
rotation (table 7.10I, p. 439). In dance, external
rotation is often added to other movements of the
arm such as shoulder flexion or abduction to create
a desired aesthetic (right arm in figure 7.30). In
sport, shoulder external rotation is incorporated
into the backhand drive in racket sports and used
in the underhand pitch. Mechanically, as previously
described, the addition of external rotation to full
shoulder abduction decreases shoulder stress and
increases possible range without undesired scapular
elevation. The shoulder external rotators—particu-
larly the infraspinatus and teres minor of the rotator
cuff (Warner et al., 1990)—would be used concentri-
cally to effect this rotation. Shoulder external rota-
tion tends to be linked with adduction of the scapula
(trapezius, rhomboids).
Shoulder Internal Rotation
In open kinematic chain movements, shoulder inter-
nal rotation refers to rotating the humerus inward
along its long axis in an approximately horizontal
plane, as when one rotates the arm inward from
anatomical position so that the point of the elbow
(olecranon process) faces outward or forward. As
with external rotation, strengthening exercises
against external resistance often incorporate a posi-
tion of elbow flexion, as in single-shoulder internal
rotation (table 7.10J, p. 440). In dance, similarly to
external rotation, internal rotation is often added
to other movements of the arm such as shoulder
flexion, extension, or abduction to create a desired
aesthetic (left arm in figure 7.31). In sport, shoulder
internal rotation is incorporated in overarm throw-
ing; certain overhead and forehand strokes in racket
sports; and the crawl, butterfly, and breaststroke in
swimming. Internal rotation of the shoulder can be
important for placement and force application of
the hand. The shoulder internal rotators—including
the subscapularis, teres major, latissimus dorsi, and
pectoralis major—could be used concentrically to
effect this rotation. The subscapularis (of the rotator
cuff) is a particularly strong internal rotator that is
capable of producing this motion in isolation. Many
of the other muscles are called into play when more
force is needed, in different joint ranges, or when a
specific combination of movements is present. For
example, the latissimus dorsi would tend to create
shoulder extension with internal rotation, whereas
the pectoralis major (clavicular portion) would tend
to produce shoulder flexion and internal rotation.
Shoulder internal rotation tends to be linked with
abduction of the scapula (serratus anterior and
pectoralis minor).Shoulder Horizontal
Adduction and AbductionAlthough not among the fundamental movement
pairs in the classic three planes associated with ball-
and-socket joints, the specialized movements of
horizontal adduction and horizontal abduction are
included because of their common use in dance.FIGURE 7.30 Sample dance movement showing shoulder
external rotation.
Photo courtesy of Patrick Van Osta. CSULB dancer Dwayne Worthington.