What Is the Lattice Muscle? Location, Function & Exercises

The term “lattice muscle” is a common shorthand for the latissimus dorsi, informally known as the “lats.” As one of the most expansive muscles of the upper body, it plays a significant part in powerful arm movements and contributes to the V-shaped torso aesthetic. The latissimus dorsi is a broad, flat muscle on the posterior trunk, covering nearly all other back muscles except for the trapezius.

Anatomy of the Latissimus Dorsi

The latissimus dorsi is distinguished by its considerable size and fan-like shape, making it the widest muscle in the human body. It originates from a wide area on the posterior torso, with fibers attaching to the spinous processes of the thoracic vertebrae T7 down to the lumbar vertebrae L5, the thoracolumbar fascia, the lower three or four ribs, and the posterior third of the iliac crest.

From these widespread points of origin, the muscle fibers converge superiorly and laterally, narrowing into a flattened tendon. This tendon twists as it approaches its insertion point on the humerus, specifically attaching to the floor of the intertubercular sulcus. This unique twisting arrangement of the tendon is believed to optimize the muscle’s leverage for powerful movements.

The muscle itself is relatively thin, which allows it to drape effectively over the underlying structures of the back. Its superficial position means it lies just under the skin and fascia, making its borders palpable, especially during contraction. The upper part of the muscle contributes to the formation of the posterior axillary fold, the fleshy area at the back of the armpit.

Primary Functions

The latissimus dorsi is a versatile muscle responsible for several powerful movements at the shoulder joint. Its primary functions are arm extension, adduction, and internal rotation. Extension occurs when you pull your arm backward, such as when reaching into the back seat of a car or during the pulling phase of a swimming stroke.

Adduction is the motion of bringing the arm toward the body’s midline, like when pulling a heavy door closed or performing a pull-up. The latissimus dorsi works with the pectoralis major and teres major muscles to generate significant adduction force. The third action is internal rotation, where the muscle turns the arm inward, rotating the shoulder so the thumb points toward the body. All three of these movements are often combined in functional activities, from throwing a ball to climbing.

Beyond moving the arm, the latissimus dorsi serves important secondary roles. It acts as a stabilizer for the scapula (shoulder blade) and the lumbar spine during various movements. In situations where the arms are fixed overhead, as in climbing, the lats can help elevate the entire trunk. It is also an accessory muscle of respiration, contributing to forceful exhalations like coughing or sneezing by compressing the rib cage.

Strengthening Exercises

One of the most effective exercises is the pull-up, or its more accessible variation, the lat pulldown. For a pull-up, grip a bar with hands wider than shoulder-width apart and palms facing away. Initiate the movement by depressing and retracting your scapulae, then pull your chest toward the bar, focusing on driving the elbows down and back. The lat pulldown machine replicates this movement, allowing for adjustable resistance.

Another foundational exercise is the bent-over row. To perform this, stand with feet shoulder-width apart, hinge at the hips until your torso is nearly parallel to the floor, and hold a barbell or dumbbells with an overhand grip. Keeping your back straight, pull the weight up toward your lower chest, squeezing your shoulder blades together at the top of the movement.

For isolating each side of the back, the single-arm dumbbell row is an excellent choice. Place one knee and the same-side hand on a flat bench for support, keeping your back flat. Hold a dumbbell in the opposite hand with your arm extended toward the floor. Pull the dumbbell up toward your hip, concentrating on retracting the shoulder blade and driving the elbow upward. This unilateral movement helps correct strength imbalances and enhances the mind-muscle connection.

Proper form is important to effectively target the lats and prevent injury. Focus on a full range of motion, allowing the lats to stretch at the bottom of the movement and fully contract at the top. Visualize using your back muscles to move the weight, rather than just pulling with your arms, to ensure the latissimus dorsi is the prime mover.

Common Issues and Pain

Problems with the latissimus dorsi often arise from overuse, improper lifting technique, or muscular imbalances. One of the most frequent issues is a muscle strain, which can range from a mild pull to a more severe tear of the muscle fibers. These injuries occur during activities that involve forceful pulling or sudden eccentric loading, such as catching a heavy object or using incorrect form during rows or pull-ups. Symptoms often manifest as a dull ache or sharp pain in the mid-back, under the armpit, or along the side of the torso.

Chronic tightness is another common complaint. When these muscles become overly tight, they can restrict the range of motion at the shoulder joint, particularly in overhead movements. This can contribute to postural problems, such as rounded shoulders, where the shoulders are pulled forward and internally rotated. This postural deviation can also lead to compensatory strain on other muscles in the neck, shoulders, and upper back.

Pain originating from the lats can sometimes be mistaken for other conditions. Weakness when performing pulling motions, tenderness to the touch along the muscle, and pain that worsens with arm extension or adduction are all indicators of a potential latissimus dorsi issue. These symptoms can impact daily activities, from reaching for an item on a high shelf to carrying groceries.