Understanding the Muscles in the Shoulder

muscles in shoulder

The muscles in the shoulder are grouped into four categories: Pectoral, Deltoid, Rotator cuff, and Triceps. To understand these muscles, it will help to know the names of their specific functions. This article will cover each type. For more information, check out our article on the different muscles in the shoulder. The muscle groups involved in shoulder flexion and abduction are the Pectoralis major, latissimus dorsi, teres major, triceps, coracobrachialis, deltoid, and supraspinatus.


The pectoralis major and minor are the two primary muscle groups of the pectoral region. Both originate from the ribs and attach to the coracoid process of the scapula. Pectoralis major plays a vital role in shoulder protraction and stabilisation. They also play a role in the elevation of the ribs during inspiration. The pectoralis major and minor work together to control the shoulder.


Pain caused by a strained deltoid muscle can make it difficult to lift or use your arm. It can also occur in a sudden, twinge-like manner during activities, and may be accompanied by swelling. In severe cases, it can even result in weakness or loss of the muscle. Treatment for deltoid muscle strains involves rehabilitation and rest. It is important to start warm up slowly before engaging in sports, especially those involving overhead movements, as well as stretching and exercise.

Rotator cuff

The four rotator cuff muscles in the shoulder perform a variety of functions during the arm and shoulder range of motion. In addition to stabilizing the glenohumeral joint, they control humeral head translation. While the supraspinatus and infraspinatus play major roles in scapular plane abduction, they generate about two to three times more force than these two muscles.


The Triceps muscles in the shoulder are divided into two heads – the lateral and the medial. The lateral head originates from the infra-glenoid tubercle on the scapula and is active during all forms of forearm extension. Both head types have an opposing action on the glenohumeral joint. During elbow extension, the lateral head pulls on the humerus and helps to hold the head of the humerus inside the glenoid cavity.

Internal intercostals

The muscles of the shoulder, known as the internal intercostals, are found between the ribs. They are innervated by intercostal nerves and receive their blood supply from the anterior and posterior intercostal arteries. During forced expiration, these muscles depress the ribs. Their origin is at the costal groove of one rib and proceed in a similar fashion, inserting on the superior border of the immediate rib.

Brachial plexus

If you’ve suffered from an injury to the brachial plexus muscles of your shoulder, you’re probably aware of the pain and limitations they can cause. If you’re not sure if this is the case, you can ask a healthcare provider for a diagnosis. If you have pain in the shoulder or arm, a physical therapist can help you with treatment options. Rehabilitation exercises can help you regain use of the arm and prevent further damage to the nerves.

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