GENERAL INFORMATION
The infraspinatus is a muscle located in the shoulder region. It is one of the four muscles that make up the rotator cuff. The infraspinatus muscle plays a vital role in shoulder movements, particularly in external rotation and stabilisation of the shoulder joint.
ORIGIN
This muscle originates from the infraspinous fossa, which is a depression on the posterior aspect of the scapula (shoulder blade).
INSERTION POINT
The muscle inserts into the greater tuberosity of the humerus (upper arm bone). It attaches to the bone via a tendon that blends with the joint capsule of the shoulder.
MAJOR ARTERIES
The infraspinatus muscle receives its blood supply from branches of the suprascapular artery as well as the circumflex scapular artery.
NEURAL INNERVATION
The infraspinatus muscle is innervated by the suprascapular nerve, which arises from the upper trunk of the brachial plexus (C5-C6).
TRIGGER POINT
Trigger points can develop in this muscle, causing localised pain and tenderness. These trigger points can be associated with muscle overuse, poor posture, or trauma.
CONCENTRIC FUNCTION
Contraction of the infraspinatus muscle initiates and assists in the external rotation of the arm. It helps to rotate the arm outward. It also stabilises the shoulder joint.
ECCENTRIC FUNCTION
The infraspinatus muscle has a crucial eccentric function during controlled shoulder movements, particularly in maintaining the inward rotation of the arm.
ISOMETRIC FUNCTION
Isometric contraction of this muscle provides stability and support to the shoulder joint, maintaining proper alignment as well as preventing excessive inward rotation.
RELATED MUSCLE SCIENTIFIC NAMES
- Infraspinatus: Also known scientifically as the “Infraspinatus muscle,” this is one of the key muscles of the rotator cuff, responsible for lateral rotation of the arm as well as stabilisation of the shoulder.
ANTAGONIST
- Subscapularis: This muscle primarily performs the medial rotation of the arm, opposing the infraspinatus.
- Pectoralis Major: A major muscle of the chest that works against the infraspinatus by internally rotating the arm.
COMMON INJURIES
- Infraspinatus Tendonitis: Characterised by inflammation due to repetitive motion or overuse, leading to pain as well as restricted movement.
- Infraspinatus Tear: This injury can range from partial to complete tears, often caused by trauma or progressive wear.
- Impingement Syndrome: Results from the compression of the infraspinatus tendon and surrounding structures, causing pain as well as limited mobility.
EXERCISES
- External Rotation with Resistance Bands: Strengthens the infraspinatus by rotating the arm outward against resistance, enhancing shoulder stability.
- Dumbbell External Rotation: This exercise targets the external rotators, fortifying the infraspinatus and improving joint support.
- Scaption: Raising the arm diagonally between abduction and flexion, this exercise engages the muscle alongside other shoulder stabilisers.
- Isometric External Rotation: Involves holding the arm in an externally rotated position against resistance, strengthening the infraspinatus.
- Wall Push-offs: Using a wall to push away gently engages the infraspinatus and other rotator cuff muscles, enhancing shoulder stability.
STRETCHES
- Cross-body Stretch: A gentle stretch for the muscle involving bringing the arm across the chest to alleviate tension in the shoulder.
- Wall Stretches: Standing at a wall, the hand is placed at shoulder height, and the body is leaned away to stretch the infraspinatus.
- Doorway Stretch: By placing both arms on a doorway frame and gently stepping forward, this stretch effectively loosens the muscle.
- Towel Stretch: Using a towel held by both hands behind the back, gently pull upward with the top hand to stretch the muscle.
- Pendulum Stretch: Leaning over slightly and allowing the arm to swing gently helps to relieve tension in the infraspinatus and enhance mobility.