A Review of the Shoulder Muscles and Their Actions

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

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 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°)

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.

Teres Major

Name the action

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 Pect. Major

SubscapularisDeltoid

Supraspinatus Teres Major

InfraspinatusTeres Minor

What position are her shoulders in?

Flexion

What position is his right shoulder in?

Horizontal Abduction andExternal 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

1.2.

FlexionExtension

Position of their shoulders?

What is the position of shoulders?

Extension

Shoulder Muscle Exercises

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

Shoulder action = ?Shoulder muscle(s) = ? Abduction

DeltoidSupraspinatus

Shoulder action = ?Shoulder muscle(s) = ?

Flexion

Ant DeltoidUpper Pect MajorCoracobrach.

Shoulder action = ?Shoulder muscle(s) = ? Horizontal Add.

Ant. DeltoidPect. Major (both)Coracobrachialis

Shoulder action = ?Shoulder muscle(s) = ? Horizontal Abduction

Latissimus DorsiPost. DeltoidTeres MinorInfraspinatus

Shoulder action = ?Shoulder muscle(s) = ?

Adduction

Pect. Major (both)CoracobrachialisLatissimus DorsiTeres Major

Shoulder action = ?Shoulder muscle(s) = ?

Horizontal Add

Ant. DeltoidPect. Major (both)Coracobrachialis

Shoulder action = ?Shoulder muscle(s) = ?

Extension Lats Teres MajorPost. Deltoid Pectoralis Major (lower)Infraspinatus Teres minor

Shoulder action = ?Shoulder muscle(s) = ?

External Rotation

InfrspinatusTeres MinorPost. Deltoid

Name a shoulder muscle isolated with the following exercises.

• 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 RotationExternal Rotation

Internal Rotation

Subscapularis, Ant. Deltoid, Pect, Major, Lats. And Teres Major

Rotator Cuff ExercisesExternal Rotation

External Rotation

Internal 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

• 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.