The teres major is a thick, rectangular muscle located in the shoulder region. While positioned near the rotator cuff muscles, it is not considered part of that group because it does not attach to the shoulder joint capsule. It contributes to various arm movements and the overall stability of the shoulder joint.
Where It Is Located
The teres major muscle originates from the posterior surface of the inferior angle of the scapula, or shoulder blade. From this point, its fibers extend upward and laterally, twisting slightly as they travel. The muscle then inserts onto the medial lip of the intertubercular groove, also known as the bicipital groove, of the humerus, which is the upper arm bone. This groove is a prominent vertical channel on the upper part of the humerus.
The teres major is situated just above the latissimus dorsi muscle, and these two muscles often work together. It is also found below the infraspinatus and teres minor muscles. Its thick, somewhat flattened shape allows it to span from the lower part of the shoulder blade to the upper arm.
What It Does
The teres major contributes to several actions at the shoulder joint. It extends the humerus, moving the arm backward. An example of this movement is pulling the arm down from an overhead position.
The muscle also facilitates adduction, pulling the arm towards the body’s midline. This action is evident in movements like bringing the arm down to the side after it has been raised. Additionally, the teres major is involved in the internal, or medial, rotation of the humerus, rotating the arm inward towards the body. These functions often occur in synergy with the latissimus dorsi. Everyday activities such as rowing, pulling, and certain swimming strokes engage the teres major.
Keeping It Healthy
Maintaining teres major health is important for shoulder function and preventing discomfort. Common issues affecting this muscle include tightness, strains, and weakness. These problems can arise from overuse, sudden forceful movements, improper lifting, or inadequate warm-up. Repetitive overhead motions, common in sports like baseball pitching or swimming, can particularly stress the teres major. Poor posture can also increase tension in this area.
To keep the teres major healthy, a balanced approach of stretching, proper posture, and strengthening is beneficial. Regular stretching helps maintain flexibility and can improve the range of motion in the shoulder, potentially reducing tension and soreness. General stretches that target the armpit area and focus on scapular alignment can be effective, such as cross-body arm reaches or overhead stretches.
Strengthening the teres major and surrounding muscles contributes to shoulder stability and can prevent injuries. General strengthening principles include incorporating movements that involve adduction, extension, and internal rotation of the arm. Exercises like seated rows or lat pulldowns can engage this muscle. Maintaining good posture and taking breaks to move and stretch also supports teres major health. If pain persists, consulting a healthcare professional is advisable for proper diagnosis and a personalized treatment plan.