A Review of the ShoulderMuscles 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 • Name the muscles for Horizontal for Horizontal Adduction Abduction• Pect Major (both) • Deltoid (post)• Corachobrachialis • Infraspinatus• Deltoid (anterior) • Teres minor • Lats
Practice• List the muscles that • List the muscles that do flexion of the do extension of the shoulder shoulder• Coracobrachialis • Latissimus dorsi• Pectoralis major • Teres major (upper to 60°) • Posterior deltoid• Anterior Deltoid • Pectoralis major (lower fibers to neutral)
Practice• List the muscles that List the muscles that do do adduction of the abduction of the shoulder shoulder• Pectoralis major • Deltoid (all sections) (lower and upper • Supraspinatus below 90°) • Pectoralis major• Coracobrachialis (upper past 90°)• Latissimus dorsi• Teres major
Practice• List the muscles that • List the muscles that do internal rotation do external rotation of the shoulder of the shoulder• Subscapularis • Infraspinatus• Latissimus dorsi • Teres minor• Teres major • Posterior deltoid• Anterior deltoid• Pect. major
Name the muscle.CoracobrachialisName the actionAdduction ofthe shoulderAlso, flexionand hor. add.
Shoulder action = ? Shoulder muscle(s) = ?Extension Lats Teres Major Post. Deltoid Pectoralis Major (lower) Infraspinatus Teres minor
Shoulder action = ? External RotationShoulder muscle(s) = ? Infrspinatus Teres Minor Post. Deltoid
Name a shoulder muscle isolatedwith 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? Whatmuscles perform that action? External Rotation Internal 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
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 shoulders 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 needsto be performedwithin 3 months orthe supraspinatusmuscle will atrophyand be too short toreattach
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.