MUSCLE:
Deltoid (Is made up of three
heads: anterior, lateral, and posterior)
Muscle:
Anterior Deltoid
Origin:
At the lateral third of the
clavicle (collar bone), on the anterior border.
Insertion:
At the deltoid
tubercle of the lateral surface of the humerus
Function:
Humeral flexion; works with
the pectoralis major in drawing the arm forward. It is a
strong abductor of the arm. The anterior deltoid’s lower
fibers weakly adduct and rotate the arm inward.
Muscle:
Lateral Deltoid
Origin:
At the acromion process on
the scapula.
Insertion:
At the deltoid
tubercle on the lateral surface of the humerus
Function:
Abduction of the humerus. It
is aided by the supraspinatus, and the upper fibers of
the anterior and posterior deltoid in abduction. It is
limited by the tightening of the lower shoulder capsule.
The lateral deltoid contracts to abduct the humerus,
while the anterior and posterior deltoid stretch to
steady the humerus.
Muscle:
Posterior Deltoid
Origin:
At the lateral aspect at the
inferior edge (below the top, outside edge of the
shoulder blade) of the spine of the scapula
Insertion:
At the deltoid
tubercle of the humerus
Function:
Humeral extension. It
assists the latissimus dorsi and teres major in drawing
the arm backward into extension. The lower fibers weakly
adduct and outwardly rotate the arm.
Indication of
Weakness: Anterior Deltoid:
Overhead presses become
difficult and painful. Acromioclavicular (AC) joint
sprain will cause weakness, since the anterior and
lateral deltoid cannot contract properly in an unstable
joint.
Shortening of the
infraspinatus and pectoralis major will decrease ROM in
arm abduction. Fixation of the scapula to the thoracic
wall can also decrease ROM in arm abduction.
The posterior deltoid is
weakened when the anterior deltoid and pectorals become
shortened and hypertonic, causing agonist-antagonist
muscle inhibition. If the glenohumeral joint has shifted
forward due to shortened muscles, it needs to be treated
or stretched to allow the posterior deltoid to contract
properly again.
Optimal Training
Principles:
The shoulder joint has the
largest range-of-motion (ROM) of all the bodies joints.
This ROM is brought about because the shoulder joint
relies on muscles and ligaments for stability, instead
of the skeletal structure. Unfortunately, this great ROM
makes the shoulder more susceptible to injury than other
joints. In order to keep the shoulder capsule healthy
and maintain optimum performance, will require you to
train all the muscles of the shoulder and rotator cuff
for both strength and flexibility.
The anterior deltoid is
often over-trained. All chest and shoulder exercises
will recruit the anterior deltoid. Bodybuilder’s target
the anterior deltoid with dumbbell front raises. These
exercises are not necessary since side lateral raises,
chest presses (particularly the incline chest press),
chest flyes and all shoulder exercises, target the
anterior deltoid.
The lateral deltoid is
stressed in barbell, dumbbell and machine shoulder
presses and dumbbell side lateral raises. To maximize
stress on the lateral deltoid during shoulder presses,
keep the elbows flared at 9 o’clock and 3 o’clock
(elbows directly out to the side). While this position
is ideal for stressing the lateral deltoid, some
athletes may find it painful and difficult, if not
impossible to get their elbows in this position. If this
is the case, elbows positioned at 4 o’clock and 8
o’clock (elbows slightly in front of the body) or 5
o’clock and 7 o’clock will make the exercise more
comfortable by taking the stress off of the shoulder
capsule. The more the elbows move anterior to the
shoulder, the less stress on the lateral head. The same
is true regardless of whether the athlete uses barbells,
dumbbells or machines. The difference is in the
stability of the shoulder press. Machines afford the
greatest stability, which is preferable for beginners.
Advanced athletes are going to need dumbbells in order
to make the exercises less stable and therefore place
more stress on the shoulder’s stabilizer muscles.
Important Safety Notes:
Keep the wrists straight,
thumbs wrapped around the bar and elbows directly under
the wrist while performing shoulder presses.
Behind-the-neck presses are considered a
“contra-indicated” exercise (high risk of injury-with
limited or no additional benefit, not recommended for
most populations).
The behind-the neck
variation places maximal stress on the cervical disks
and muscles attached to the cervical disks and increases
the risk of cervical disk herniation and rupture. It
also places maximal stress on the shoulder capsule.
The side lateral raise is an
excellent isolation exercise for the lateral deltoid.
This can be performed on machines or with dumbbells
(dumbbells will work the important stabilizer muscles
surrounding the shoulder capsule).
Dumbbell side raise with the
hands at 3 o’clock and 9 o’clock places maximal stress
on the lateral deltoid, but just like the shoulder
press, some athletes may find this position
uncomfortable or painful. The 4 o’clock - 8 o’clock or 5
o’clock - 7 o’clock positions will reduce both the
stress on the shoulder capsule (increasing safety and
comfort) and the lateral deltoid (decreasing
effectiveness).
Important Safety Notes:
It is recommended for both
safety and comfort that the elbows remain slightly bent
(10-15 degrees) through-out the exercise, you do not
raise the elbow above shoulder level and you avoid the
“pouring tea variation” (bodybuilders like to rotate the
hand at the top of the movement by rotating the little
finger up and thumb down -simulating pouring tea). These
3 violations of safety guidelines cause shoulder
impingement and elbow stress.
One thing you may want to
consider for your athletes is to have them perform their
side raises with their knees bent (5-15 degrees) and
angled slightly forward from the waist (5-15 degrees)
while maintaining weight-lifters arch and good posture
(scapula retraction). The lateral deltoid in many
athletes is more posterior than directly lateral and
this position will enable them to more directly stress
the lateral head.
Bent-Over-Lateral-Raises
target the posterior deltoid. It is recommended that you
use a “high-bench” or sit at the end of a bench with the
dumbbells moving under the thighs. Many athletes will
find bent-over-lateral-raises stressful on the lower
back. If no bench is available, have the athletes bend
their knees (10-30 degrees) depending on comfort and
flexibility), maintain good weight-lifters arch and
scapula retraction. Maximize stress on the posterior
deltoid by keeping the back parallel to the floor (bend
knees for comfort), maintaining the hands in line with
the shoulders and contracting the posterior deltoid
until the arms are parallel to the floor. Good chest and
shoulder flexibility will be needed to keep hands in
line with shoulders and contract through full ROM. The
exercise becomes less effective if the hands move behind
the shoulders, you lock your elbows or you raise your
torso above parallel to the floor.
Important Safety Notes:
Losing the weight-lifters
arch and/or knee bend stresses the low back and hip
joints. Locking the elbows stress the elbow joints.
Performing the “pouring tea variation” stresses the
shoulder joint.
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For more
detail on the entire Building Bigger Stronger Muscles
FITBIT Series, attend the IFPA Fitness By the Bay
Conference, September 14 – 16, 2006 in Tampa, FL. For
more information
CLICK HERE
or call (800) 785-1924 to register.
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James
T. Bell, PhD is the
founder and president of the International Fitness
Professionals Association, IFPA.
More
Books from Jim Bell, PhD
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