The Upper Extremity 397of the scapula (figure 7.21C). The location of the
serratus anterior (figure 7.21D) allows it to be a key
abductor of the scapula, and hence this muscle can
be recruited and strengthened by focusing on keep-
ing the scapula “wide” (scapular abduction) versus
allowing them to “pinch together” (scapular adduc-
tion) while performing a push-up (figure 7.21E)
and by adding a little extra push at the top of the
push-up, further abducting the scapulae (termed a
“push-up plus,” table 7.10A, variation 1, p. 434). In
contrast, if the trapezius is not functioning prop-
erly, the unopposed action of the serratus anterior
during elevation of the arm will tend to depress the
scapula, abduct the scapula, and produce a back-
ward projection of the inferior angle of the scapula
(figure 7.21F). Since the trapezius’ location allows
it to function as a powerful adductor of the scapula
(figure 7.21G), performing sitting rowing exer-
cises with a band (figure 7.21H and table 7.10D,
variation 2, p. 435) or prone rowing exercises with
a weight while focusing on keeping the elbows at
shoulder height as they are brought slightly behind
the torso as the shoulder blades are pulled together
(scapular adduction) can be used to recruit and
strengthen this muscle. However, a winged scapula
may also relate to other medical conditions including
scoliosis or nerve injury, and if the winging is marked,
evaluation by a physician is recommended.
Shoulder Mechanics
Coordinated movements between the shoulder
girdle and arms are essential for optimal move-
ment and preventing injuries. The scapulohumeral
rhythm, combined external rotation with shoulder
abduction, the SIT force couple, and synergies are
utilized to foster this coordinated functioning of the
shoulder complex.Scapulohumeral Rhythm
Because the shallow glenoid cavity has contact with
only about one-third of the surface area of the head
of the humerus, the glenohumeral joint is rather
susceptible to subluxation or dislocation. Hence,
coordinated movements of the scapula are vital to
position the glenoid cavity so that adequate contact
with the head of the humerus can be maintained and
the desired large range of movement of the humerus
can be facilitated while the costal surface of the
scapula is still kept in close contact with the thorax.
This movement of the scapula also often works to
help keep the prime movers at the shoulder joint at
a favorable length to generate force and avoid active
or passive insufficiency. This precisely coordinated,
synchronous movement between the scapula and the
humerus is termed the scapulohumeral rhythm.
This scapulohumeral rhythm involves character-
istic scapular movements that supplement specific
humeral movements. The most commonly discussed
linking is the upward rotation of the scapula that
accompanies shoulder abduction as shown in figure
7.22. After the initial movement of the arm that pre-
dominantly occurs at the glenohumeral joint, there
is a linked relationship between upward rotation of
the scapula and elevation of the arm such that after
about 30° of abduction or 45° to 60° of flexion there
is about 3° of glenohumeral motion for every 2° of
scapular motion. So, with the total range of 180°
flexion or abduction, the glenohumeral-to-scapula
ratio is 2:1, that is, about 120° of glenohumeral
motion and 60° of scapular motion as shown in figure“Pull Your Shoulders Back”
T
he directive to “pull your shoulders back” or “pull your shoulders back and lift your chest” is
sometimes used by teachers in response to a student with rolled shoulders and functional kypho-
sis. One desired anatomical interpretation of this cue is to emphasize using the scapular adductors
to help bring the shoulders to a desirable position and the thoracic spinal extensors to help correct
the rounded upper back. However, some students respond to this directive by pinching the shoulder
blades together (excessive scapular adduction) and “rib-leading” (excessive lumbar extension versus
the desired upper thoracic extension). In such cases, cueing to “reach the shoulders to the side” as the
upper back “lifts up toward the ceiling” or to bring the shoulder blades slightly down and together as
the shoulders reach to the side may help achieve the desired placement.