Module 2 Muscle Actions

Pectoralis major

Shoulder adduction, internal rotation, extension from flexed (sternocostal head) & flexion from extension (clavicular head)

Pectoralis Minor

Stabilizes scapula by drawing it inferiorly and anteriorly

Subclavius

Depresses and stabilizes clavicle

Serratus Anterior

Scapular protraction and upward rotation

Upper trapezius

Bilateral: extension of head and neck
Unilateral: lateral flexion, contralateral rotation, scapular elevation, and upward rotation

Middle Trapezius

Scapular retraction and stabilization

Lower trapezius

Scapular depression and upward rotation

Latissimus Dorsi

Shoulder extension, adduction, and internal rotation

Levator Scapulae

Scapular elevation & downward rotation, head and neck extension, lateral neck flexion, ipsilateral head rotation

Rhomboids

Scapular retraction and downward rotation

Supraspinatus

Assists deltoid in shoulder abduction, stabilizes GH

Infraspinatus

Shoulder external rotation, stabilizes GH

Teres minor

Shoulder external rotation, stabilizes GH

Subscapularis

Shoulder internal rotation, adduction, stabilizes GH

Anterior deltoid

Shoulder flexion, abduction, and internal rotation

Middle deltoid

Shoulder abduction

Posterior deltoid

Shoulder extension, abduction, and external rotation

Teres Major

Shoulder abduction and internal rotation

Biceps brachii

Forearm supination, flexion of elbow (when supine)

Brachialis

Elbow flexion (in all positions)

Coracobrachialis

Assists with shoulder flexion & adduction, resists shoulder dislocation

Triceps Brachii

Elbow extension, extends shoulder & resists shoulder dislocation (long head)

Anconeus

Assists in elbow extension, elbow stabilizer, adducts ulna in protraction