The Teres Major is a thick, yet somewhat flattened, muscle of the upper limb that plays a significant role in shoulder movement and stability. Although located near the rotator cuff, it is not technically part of that group because it does not attach to the shoulder capsule. The muscle bridges the shoulder blade to the upper arm bone, forming a substantial part of the back of the armpit. Because it works closely with the much larger Latissimus Dorsi muscle, the Teres Major has earned the nickname “The Lat’s Little Helper.” This muscle is primarily a mover of the arm, allowing for strong, coordinated actions that pull the arm toward the body.
Understanding Its Anatomical Placement
The Teres Major muscle is situated in the upper posterior region of the torso, inferior to its smaller neighbor, the Teres Minor. It acts as a powerful connector between the shoulder blade (scapula) and the upper arm bone (humerus). The muscle’s origin point, the stable attachment, is found on the posterior surface of the inferior angle of the scapula, which is the bottom tip of the shoulder blade.
From this origin, the muscle fibers travel upward and laterally, wrapping slightly around the front of the humerus bone. The muscle’s insertion point is the medial lip of the intertubercular groove of the humerus, sometimes called the bicipital groove. This insertion point is shared with the Latissimus Dorsi and Pectoralis Major muscles, creating a powerful attachment site on the arm. This specific anatomical arrangement dictates the muscle’s mechanical advantage.
Primary Roles in Arm Movement
The primary function of the Teres Major is to execute three major movements of the arm at the glenohumeral joint: adduction, medial rotation, and extension of the humerus. It works as a synergist, meaning it assists the Latissimus Dorsi in performing these actions.
Adduction involves pulling the arm toward the midline of the body, such as when bringing the arm down from an overhead position or pulling a rope toward the torso. Medial rotation (internal rotation) is the action of turning the arm inward, rotating the palm toward the body when the elbow is bent. Extension is the movement of drawing the arm backward, especially when moving the arm from a flexed position. This powerful action is used in activities like rowing or the pulling phase of a pull-up.
Strategies for Muscle Health and Recovery
Maintaining the health of the Teres Major involves a balanced approach to both strengthening and stretching. Since its function is closely integrated with the larger back and shoulder muscles, strengthening exercises should mimic its primary functions of pulling and drawing the arm toward the body.
Exercises like the single-arm dumbbell row or the seated cable row are effective, as they require pulling a weight while focusing on retracting the shoulder blade. The Lat Pulldown, especially with a neutral or underhand grip, strongly engages the Teres Major as it works with the Latissimus Dorsi to pull the arms down. When performing these movements, concentrating on pulling with the elbow and squeezing the shoulder blades helps maximize activation.
Stretching is important to prevent tightness, which can limit the shoulder’s range of motion and contribute to poor posture. A simple and effective stretch is the cross-body arm reach, where the arm is brought across the chest and gently pulled closer with the opposite hand. Another useful technique is a modified overhead triceps stretch, where the opposite hand gently pulls the bent elbow across the midline of the body.
Foam rolling the upper back and the area just below the armpit can help relieve tension in the Teres Major and reduce trigger points. Prevention of strain requires avoiding sudden, uncontrolled movements and ensuring proper form during lifting exercises. Consistent warm-ups with light arm swings and gentle stretching before activity prepare the Teres Major for work, mitigating the risk of overuse injuries.