Massage Therapy Journal Spring 2025

52 • Massage Therapy Journal

AMTA Continuing Education

It may also aid with elevating the ribs during forced inhalation. 30 Deltoid The deltoid muscle is a large triangular muscle located in the shoulder region. It is a key muscle responsible for a variety of movements of the glenohumeral joint. This muscle has three different portions that have different actions. 1. Anterior deltoid originates on the lateral third of the clavicle and inserts on the deltoid tuberosity of the humerus. This muscle produces flexion, medial rotation and horizontal adduction of the glenohumeral joint. 2. Middle deltoid originates on the lateral aspect of the acromion process of the scapula and inserts on the deltoid tuberosity of the humerus. When middle deltoid contracts, abduction of the glenohumeral joint is produced. 3. Posterior deltoid originates on the spine of the scapula and inserts on the deltoid tuberosity of the humerus. This muscle is responsible for extension, lateral rotation and horizontal abduction of the glenohumeral joint. 31 Coracobrachialis The coracobrachialis muscle is located in the upper arm and is deep to the biceps brachii and anterior deltoid. This muscle originates on the coracoid process of the scapula and inserts on the medial aspect of the mid-humeral area. When the coracobrachialis contracts, flexion and adduction of the glenohumeral joint is produced. 32 Supraspinatus, Infraspinatus, Teres Minor and Subscapularis (SITS) This group of muscles is most commonly known as the rotator cuff muscle group. Each muscle has functions to move the glenohumeral joint, but collectively they stabilize the head of the humerus in the glenoid fossa of the scapula. The supraspinatus is the first “S” in the acronym for the rotator cuff group. The origin is in the supraspinous fossa of the scapula, and it

inserts on to the greater tubercle of the humerus. Its function is to produce abduction of the glenohumeral joint. 33 The infraspinatus is the ‘I’ in the acronym for the rotator cuff group. This muscle originates in the infraspinous fossa of the humerus and inserts on to the greater tubercle of the humerus. Its function is to produce lateral rotation, adduction and extension of the glenohumeral joint. 34 The teres minor is the ‘T’ in the rotator cuff muscle group acronym. This muscle begins on the upper two-thirds of the lateral border of the scapula and inserts onto the greater tubercle of the humerus. When this muscle contracts, its function is to create lateral rotation, adduction and extension of the glenohumeral joint. 35 The subscapularis muscle is the second “S” in the rotator cuff muscle group acronym. Its origin is on the subscapular fossa of the scapula and its insertion is on the lesser tubercle of the humerus. The function of this muscle is to medially rotate the glenohumeral joint. 36 Latissimus Dorsi The latissimus dorsi is a strong, broad, flat muscle located in the lower to middle back. It is one of the major muscles of the back and plays a key role in various movements of the glenohumeral joint. The origin of latissimus dorsi is the spinous process of the last six thoracic vertebrae, last three to four ribs, the thoracolumbar aponeurosis and the posterior iliac crest. This muscle inserts onto the intertubercular groove of the humerus. When this muscle contracts, it creates adduction, medial rotation and extension of the glenohumeral joint. 37 Teres Major The teres major is a muscle located on the posterior aspect of the shoulder region. It is similar in some ways to the latissimus dorsi in its insertion and actions. The origin of the teres major muscle is on the inferior angle and lateral border of the scapula, and the insertion is near the crest of the lesser tubercle of the humerus. Its actions

amtamassage.org/mtj