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A Review of the Shoulder Muscles and Their Actions
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Questions• 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
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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
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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)
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Practice
• List the muscles that do adductionadduction of the shoulder
• Pectoralis major (lower and upper below 90°)
• Coracobrachialis• Latissimus dorsi• Teres major
List the muscles that do abductionabduction of the shoulder
• Deltoid (all sections)• Supraspinatus• Pectoralis major
(upper past 90°)
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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
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Name the muscle.
Coracobrachialis
Name the action
Adduction of the shoulder
Also, flexion and hor. add.
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Name the muscle.
Pectoralis Major
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Name the muscle.
Subscapularis
Name the action
Internal rotation of the shoulder
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Name the muscle.
Deltoid
Name the action
Abduction of shoulder
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Name the muscle.
Infraspinatus
Name the action
External rotation
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Name the muscle.
Teres Major
Name the action
Adduction of scapula
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Name the muscle.
Teres Minor
Name the action if the humerus move directly to the posterior
Extension of the shoulder
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Name the muscle.
Supraspinatus
Name the action
Abduction of the shoulder
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Coracobrachialis Pect. Major
SubscapularisDeltoid
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Supraspinatus Teres Major
InfraspinatusTeres Minor
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What position are her shoulders in?
Flexion
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What position is his right shoulder in?
Horizontal Abduction andExternal Rotation
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What rotation action is his shoulder performing as he continues to through the ball?
Internal Rotation
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What position are her shoulders in?
Flexion
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What position are his shoulders in?
Horizontal abduction or Extension
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1.2.
FlexionExtension
Position of their shoulders?
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What is the position of shoulders?
Extension
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Shoulder Muscle Exercises
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Major Muscles of the Shoulder
• Pectoralis major– Push-ups– Pull-ups– Bench press– Throwing– Tennis serve
• Latissimus dorsi– Chinning– Robe climb– Dips on parallel bars– Pullover exercises– Pulldown exercises– Rowing
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Shoulder action = ?Shoulder muscle(s) = ? Abduction
DeltoidSupraspinatus
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Shoulder action = ?Shoulder muscle(s) = ?
Flexion
Ant DeltoidUpper Pect MajorCoracobrach.
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Shoulder action = ?Shoulder muscle(s) = ? Horizontal Add.
Ant. DeltoidPect. Major (both)Coracobrachialis
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Shoulder action = ?Shoulder muscle(s) = ? Horizontal Abduction
Latissimus DorsiPost. DeltoidTeres MinorInfraspinatus
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Shoulder action = ?Shoulder muscle(s) = ?
Adduction
Pect. Major (both)CoracobrachialisLatissimus DorsiTeres Major
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Shoulder action = ?Shoulder muscle(s) = ?
Horizontal Add
Ant. DeltoidPect. Major (both)Coracobrachialis
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Shoulder action = ?Shoulder muscle(s) = ?
Extension Lats Teres MajorPost. Deltoid Pectoralis Major (lower)Infraspinatus Teres minor
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Shoulder action = ?Shoulder muscle(s) = ?
External Rotation
InfrspinatusTeres MinorPost. Deltoid
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Name a shoulder muscle isolated with the following exercises.
• Side arm dumbbell raises
• Deltoid
• Push-ups
• Pectoralis major
• Rowing and pull-overs
• Latissimus dorsi
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What is the action to the left? What muscles perform that action?
Internal RotationExternal Rotation
Internal Rotation
Subscapularis, Ant. Deltoid, Pect, Major, Lats. And Teres Major
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Rotator Cuff ExercisesExternal Rotation
External Rotation
Internal Rotation
Abduction (to work the supraspinatus)
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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
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• 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
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Shoulder Dislocation
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Impingement Syndrome
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Impingement Syndrome• A condition that decreases
the subacromial space– Acromion process– Coracoacromial ligament
• Causes– Swelling– Bone spurs– Anatomical structure
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Impingement Syndrome
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Rotator Cuff Tears
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Rotator cuff
• Subscapularis• Supraspinatus• Infraspinatus• Teres minor
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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.
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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.
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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.
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Note: Surgery needs to be performed within 3 months or the supraspinatus muscle will atrophy and be too short to reattach
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Glenoid Labrum
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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.
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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.