A Review of the Shoulder
Muscles and Their Actions
Questions
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What muscle works closely with the anterior deltoid?
Pectoralis major
What muscle is involved in any lifting movements?
Deltoid
What is the major (strongest) extensor muscle?
Latissimus Dorsi
Name the four rotator cuff muscles.
Subscapularis, Supraspinatus, Infraspinatus, and Teres
minor.
• What muscle works closely with the infraspinatus?
• Teres minor
Practice
• Name the muscles
for Horizontal
Adduction
• Pect Major (both)
• Corachobrachialis
• Deltoid (anterior)
• Name the muscles
for Horizontal
Abduction
• Deltoid (post)
• Infraspinatus
• Teres minor
• Lats
Practice
• List the muscles that
do flexion of the
shoulder
• Coracobrachialis
• Pectoralis major
(upper to 60°)
• Anterior Deltoid
• List the muscles that
do extension of the
shoulder
• Latissimus dorsi
• Teres major
• Posterior deltoid
• Pectoralis major
(lower fibers to
neutral)
Practice
• List the muscles that
do adduction of the
shoulder
• Pectoralis major
(lower and upper
below 90°)
• Coracobrachialis
• Latissimus dorsi
• Teres major
List the muscles that do
abduction of the
shoulder
• Deltoid (all sections)
• Supraspinatus
• Pectoralis major
(upper past 90°)
Practice
• List the muscles that
do internal rotation
of the shoulder
• Subscapularis
• Latissimus dorsi
• Teres major
• Anterior deltoid
• Pect. major
• List the muscles that
do external rotation
of the shoulder
• Infraspinatus
• Teres minor
• Posterior deltoid
Name the muscle.
Coracobrachialis
Name the action
Adduction of
the shoulder
Also, flexion
and hor. add.
Name the muscle.
Pectoralis Major
Name the muscle.
Subscapularis
Name the action
Internal
rotation of the
shoulder
Name the muscle.
Deltoid
Name the action
Abduction of
shoulder
Name the muscle.
Infraspinatus
Name the action
External
rotation
Name the muscle.
Name the action
Teres Major
Adduction of
scapula
Name the muscle.
Teres Minor
Name the action if the humerus move directly to the posterior
Extension of the shoulder
Name the muscle.
Supraspinatus
Name the action
Abduction of the shoulder
Coracobrachialis
Subscapularis
Pect. Major
Deltoid
Supraspinatus
Teres Major
Infraspinatus
Teres Minor
What position are her shoulders in?
Flexion
What position is his right shoulder in?
Horizontal Abduction and
External Rotation
What rotation action is his shoulder performing as he
continues to through the ball?
Internal Rotation
What position are her shoulders in?
Flexion
What position are his shoulders in?
Horizontal abduction or Extension
Position of their shoulders?
1.
Flexion
2.
Extension
What is the position of shoulders?
Extension
Shoulder Muscle Exercises
Major Muscles of the Shoulder
• Pectoralis major
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Push-ups
Pull-ups
Bench press
Throwing
Tennis serve
• Latissimus dorsi
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Chinning
Robe climb
Dips on parallel bars
Pullover exercises
Pulldown exercises
Rowing
Shoulder action = ?
Shoulder muscle(s) = ?
Abduction
Deltoid
Supraspinatus
Shoulder action = ?
Shoulder muscle(s) = ?
Flexion
Ant Deltoid
Upper Pect Major
Coracobrach.
Shoulder action = ?
Shoulder muscle(s) = ?
Horizontal Add.
Ant. Deltoid
Pect. Major (both)
Coracobrachialis
Shoulder action = ?
Shoulder muscle(s) = ?
Horizontal Abduction
Latissimus Dorsi
Post. Deltoid
Teres Minor
Infraspinatus
Shoulder action = ?
Shoulder muscle(s) = ?
Adduction
Pect. Major (both)
Coracobrachialis
Latissimus Dorsi
Teres Major
Shoulder action = ?
Shoulder muscle(s) = ?
Horizontal Add
Ant. Deltoid
Pect. Major (both)
Coracobrachialis
Shoulder action = ?
Shoulder muscle(s) = ?
Extension
Lats
Post. Deltoid
Infraspinatus
Teres Major
Pectoralis Major (lower)
Teres minor
Shoulder action = ?
Shoulder muscle(s) = ?
External Rotation
Infrspinatus
Teres Minor
Post. Deltoid
Name a shoulder muscle isolated
with the following exercises.
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Side arm dumbbell raises
Deltoid
Push-ups
Pectoralis major
Rowing and pull-overs
Latissimus dorsi
What is the action to the left? What
muscles perform that action?
Internal Rotation
External Rotation
Internal Rotation
Subscapularis, Ant. Deltoid, Pect, Major, Lats. And Teres Major
Rotator Cuff Exercises
External Rotation
Internal Rotation
External Rotation
Abduction (to work the supraspinatus)
Shoulder Related Injuries
• The shoulder is built
for motion, not stability
• Injury rate depends
on…
– Shallowness of glenoid
fossa
– Laxity of ligaments
– Strength of muscles
• Shoulder subluxation
– Incomplete or partial dislocation
• Shoulder dislocation
– Complete dislocation of the GH joint
– Most common anteriorly and inferiorly
• Shoulder separation
– Complete dislocation of the AC joint
Shoulder Dislocation
Impingement Syndrome
Impingement Syndrome
• A condition that decreases
the subacromial space
– Acromion process
– Coracoacromial ligament
• Causes
– Swelling
– Bone spurs
– Anatomical structure
Impingement Syndrome
Rotator Cuff Tears
Rotator cuff
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Subscapularis
Supraspinatus
Infraspinatus
Teres minor
Movement of RC Muscles
• Subscapularis is an
internal rotator of the arm.
• Supraspinatus assists the
deltoid in abducting the
arm, with its greatest
contribution being the
initiation of abduction.
• Infraspinatus and teres
minor muscles both
externally rotate the arm.
Rotator Cuff Injury
• The throwing motion has been divided
into five phases: wind-up, cocking,
acceleration, and follow-through.
• Cocking phase
– Subscapularis fires in late cocking phase
to decelerate the shoulder's external
rotation. Also, it is stretched during the
cocking phase.
Rotator Cuff Injury
• Follow-through (muscles fire most
intensely)
– Subscapularis internally rotates the shoulder,
– The infraspinatus and teres minor contract
eccentrically to decelerate the arm and are
stretched.
• During this repetitive eccentric loading, the
rotator cuff is prone to overload, fatigue,
tendinitis, and even a partial undersurface
tear.
Note: Surgery needs
to be performed
within 3 months or
the supraspinatus
muscle will atrophy
and be too short to
reattach
Glenoid Labrum
Labral Tear
• The glenoid cavity makes up the “socket” of the shoulder
joint.
• The labrum acts sort of like a gasket, turning the flat
surface of the glenoid into a deeper socket that molds to
the head of the humerus for a better fit.
• A tear of labrum can cause pain and a catching
sensation with movement of the shoulder.
Labral Tear
• Most labral tears are probably the result of an injury to the
shoulder, such as falling on an outstretched hand.
• There is reason to believe that the excess motion of the
humerus moving around on the glenoid may cause
damage to the labrum over time.
• An unstable shoulder may also cause injury to the labrum,
if it repeatedly dislocates out of the glenoid.