Infraspinatus
Region
Origin & Insertion
['Origin: Infraspinous fossa of scapula', 'Insertion: Middle facet of greater tubercle of humerus']
Synergistic Muscles
['Teres minor', 'Posterior deltoid']
Joints
['Glenohumeral joint']
Primary Actions
['External rotation of shoulder']
Nerve & Spinal Segment
Suprascapular nerve
Brachial plexus; C5–C6
Interesting
Key stabilizer during shoulder external rotation. [Clinically Oriented Anatomy]
Reversal of Action
Thoracic rotation initiated from shoulder
Common Dysfunctions
Weak external rotation, rotator cuff syndrome
How to Stretch
Cross arm stretch with humeral internal rotation.
Trigger Points
How to Strengthen
Theraband or dumbbell ER.
Concentric Action
External rotation of humerus
Applications:
Key in shoulder stability, injury prevention during overhead activities
Eccentric Action
Control internal rotation of shoulder
Isotonic Action
External rotation with band or dumbbell
Related Conditions
['Rotator cuff syndrome', 'Posterior shoulder pain']
Isometric Action
Hold external rotation against resistance
Exercise Ideas
['ER at 90°', 'Side-lying ER', 'Cable ER pulls']