action of infraspinatus
Laterally rotates humerus
The infraspinatus is one of the four rotator cuff muscles located in the shoulder joint. It arises from the infraspinous fossa of the scapula (shoulder blade) and inserts on the greater tubercle of the humerus (upper arm bone).
The main action of the infraspinatus muscle is to externally rotate the shoulder joint. This means that when the muscle contracts, it rotates the arm outwards. Additionally, the infraspinatus muscle also helps to stabilize the shoulder joint by preventing excessive movement.
The infraspinatus muscle is involved in many functional movements, including throwing, lifting, and pulling. If the muscle is weak or injured, it can lead to shoulder pain, weakness, and instability. Therefore, it is important to strengthen and maintain the infraspinatus muscle to prevent injury and maintain optimal shoulder function.