The Teres Major muscle is a significant component of the shoulder girdle, often overshadowed by larger muscles like the Latissimus Dorsi. It plays a substantial part in the powerful movements of the arm and overall shoulder stability. The muscle is a thick, somewhat flattened structure that helps link the shoulder blade to the upper arm bone.
Defining the Muscle’s Location
The Teres Major muscle is situated on the posterior, or back, side of the body, extending across the shoulder blade. It originates from the posterior surface of the inferior angle of the scapula, which is the lower tip of the shoulder blade. From this point, the muscle fibers run upward and laterally toward the arm.
The muscle’s fibers insert onto the medial lip of the intertubercular sulcus of the humerus, a groove on the front of the upper arm bone. Due to its functional similarity and close anatomical relationship with the Latissimus Dorsi, the Teres Major is commonly referred to as “The Lat’s Little Helper.”
Despite its name and proximity to the Teres Minor, the Teres Major is not considered one of the four rotator cuff muscles. The rotator cuff muscles attach to the shoulder joint capsule for rotation and stabilization, while the Teres Major primarily acts as a powerful mover of the arm. It is, however, one of the seven scapulohumeral muscles that connect the scapula to the humerus.
The Role in Movement
The Teres Major is a primary mover of the arm at the glenohumeral, or shoulder, joint, executing three distinct actions. The first is adduction, which involves pulling the arm inward toward the midline of the body. This action is used in movements like pulling a rope or bringing the arms down from an overhead position.
The muscle also contributes significantly to extension of the arm, the motion of moving the arm backward. The Teres Major is also a medial rotator, meaning it rotates the upper arm inward toward the chest. This inward rotation is involved in actions such as a throwing motion or reaching behind the back.
The Teres Major works synergistically with the much larger Latissimus Dorsi muscle, which shares the same actions of adduction, extension, and medial rotation. When you perform a rowing motion or a pull-up, both of these muscles are actively engaged to powerfully draw the arm down and back.
Addressing Pain and Injury
The Teres Major muscle is susceptible to pain, often presenting as a strain or tear, particularly in individuals involved in overhead sports like baseball or swimming. Symptoms typically include a dull ache or sharp pain located in the upper back, near the shoulder blade, and sometimes radiating down the arm. A strain can make overhead activities or lifting heavy objects extremely difficult and painful.
Common causes of Teres Major injury include sudden, forceful movements, repetitive overuse, or poor technique during physical activity. Trigger points, which are tight, painful knots within the muscle, are also a frequent source of discomfort. Initial treatment for a minor strain generally follows the RICE principle: rest, ice application to reduce swelling, and gentle movement.
If pain persists or movement is severely limited, seek professional guidance to rule out more serious issues. Pain may be accompanied by tenderness upon pressing the muscle, and sometimes difficulty with internal rotation of the arm. Addressing poor posture and ensuring a proper warm-up before exercise can help mitigate the risk of developing a strain or myofascial pain syndrome.
Strengthening and Maintenance
Maintaining a healthy Teres Major is accomplished through a combination of targeted strengthening and flexibility exercises. Exercises that mimic the muscle’s natural actions of pulling the arm toward the body are effective for building strength. Examples include resistance band rows, lat pulldowns, and single-arm dumbbell rows.
When performing these exercises, focus on proper form and engaging the back muscles to maximize Teres Major activation. For instance, during a lat pulldown, pulling the bar down toward the chest while keeping the elbows pointing downward specifically targets this muscle. The cable straight-arm pulldown can also help isolate the muscle for strengthening.
Stretching is equally important for maintaining mobility and preventing tightness. A simple standing stretch involves raising one arm and gently pulling the elbow across the body to feel a stretch along the back of the shoulder. Consistent stretching and strengthening help ensure the Teres Major can effectively stabilize the shoulder joint and execute powerful arm movements without undue strain.