The Deltoid Group
T
he Deltoid Group has fibers running in three different direc-
tions and three names according to location (anterior, middle,
and posterior). The anterior and posterior deltoid muscles act as
stabilizers and synergist muscles during shoulder abduction.When performing a lateral raise, it
is important to hold the shoulder
joint in neutral or in slight external
rotation. This is because abduc-
tion of the shoulder joint in an in-
ternally rotated posture increases
the risk of damage to the rotator
cuff musculature, largely due to
impingement of the rotator cuff
muscles between the acromion
and the greater tubercle of the
Humerus. Therefore, the trainer
should typically recommend that
during a lateral raise, the client
hold the weight with the thumbs
towards the ceiling or with palms
up.Although strengthening of the
Latissimus Dorsi is important, the personal trainer must keep in
mind the insertion of the Latissimus Dorsi and how tightness in
the muscle affects standing and sitting posture. The muscle belly
actually travels under the humerus and inserts onto the upper,
anterior part of the humerus. It is because of this attachment,
that the Latissimus Dorsi causes medial rotation of the Humerus.The Latissimus Dorsi is often grouped as a back muscle and
strengthening of the back muscles is thought to improve posture.
The opposite is true for the lats because without proper flexibility,
the outcome is an exaggeration of rounded shoulders and kypho-
sis of the spine. A layman’s term used for this posture is gorilla
stance because often people that overly train the lats will present
with medially rotated humerus’ and pronated palms resulting in
their thumbs pointing to their thighs when their arms are hanging
at their sides in a resting position.Seated Row
Chapter 4 Anatomy and Physiology of the Muscles
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