Latissimus Dorsi: Concentric Function, Anatomy, and Exercises

What is the concentric function of the latissimus dorsi?

The latissimus dorsi's primary concentric functions involve powerful movements of the shoulder joint: shoulder adduction, shoulder extension, and shoulder internal (medial) rotation. During concentric contraction, the muscle shortens, pulling its insertion point (the bicipital groove of the humerus) towards its origins on the torso, generating force to execute these actions.

Understanding Muscle Contraction: Concentric vs. Eccentric

To fully grasp the latissimus dorsi's concentric function, it's essential to differentiate between the types of muscle contractions.

• Concentric Contraction: This occurs when a muscle shortens under tension, generating force to overcome resistance. It's the "lifting" or "pulling" phase of an exercise, where the muscle fibers are actively contracting and becoming shorter. For example, during the upward phase of a bicep curl, the biceps brachii contracts concentrically.
• Eccentric Contraction: This is when a muscle lengthens under tension, often acting as a brake to control movement against gravity or resistance. It's the "lowering" or "resisting" phase, where the muscle is still active but is being stretched.
• Isometric Contraction: In this type, the muscle generates force without changing length, such as when holding a heavy object stationary.

When we discuss the "concentric function," we are specifically referring to the movements the latissimus dorsi initiates and executes as it shortens.

Anatomy and Origins of the Latissimus Dorsi

The latissimus dorsi, often simply called "the lats," is the largest muscle in the upper body by surface area, covering a significant portion of the back. Its broad, flat shape is crucial to its diverse functions.

• Origins: The lats originate from a wide area, including the spinous processes of the lower six thoracic vertebrae, all lumbar vertebrae, the sacrum (via the thoracolumbar fascia), the posterior iliac crest, and typically the lower three or four ribs.
• Insertion: From these extensive origins, the muscle fibers converge to a narrow tendon that inserts into the intertubercular (bicipital) groove of the humerus (upper arm bone).

This broad origin and specific insertion point dictate the powerful actions the latissimus dorsi can perform on the shoulder joint.

The Concentric Actions of the Latissimus Dorsi

During a concentric contraction, the latissimus dorsi shortens, pulling the humerus towards the torso. This action results in several key movements at the glenohumeral (shoulder) joint:

• Shoulder Adduction: This is the movement of the arm towards the midline of the body, or bringing the arm down from an overhead or abducted position. Imagine pulling your elbow close to your side. The lats are a primary mover in this action.
• Shoulder Extension: This involves moving the arm backward or downwards from a flexed (forward) position. For example, pulling your arm from in front of your body to beside or behind it. The lats are a powerful extensor, especially when the arm is already in a flexed position.
• Shoulder Internal (Medial) Rotation: This is the rotation of the humerus inward, turning the palm of the hand towards the body when the arm is at 90 degrees of abduction. While other muscles contribute, the lats play a significant role, particularly in conjunction with adduction and extension.
• Depression of the Scapula: Although the latissimus dorsi primarily acts on the humerus, its extensive attachment to the thoracolumbar fascia and lower ribs allows it to contribute indirectly to the depression of the scapula (shoulder blade), particularly in closed-chain movements or when the humerus is fixed.
• Pelvic Elevation (Reverse Action): In a "reverse action" scenario, where the arm is fixed (e.g., during a pull-up or climbing), the latissimus dorsi can pull the torso and pelvis upwards towards the arm. This is a critical function in movements where the body moves relative to a fixed limb.

Common Exercises Emphasizing Latissimus Dorsi Concentric Function

Understanding these actions allows for targeted training of the lats. Many common back exercises primarily engage the latissimus dorsi in its concentric phase:

• Pull-ups/Chin-ups: As you pull your body upwards towards the bar, the lats concentrically adduct and extend the shoulders, pulling the humerus down and back. The reverse action of the lats is particularly evident here.
• Lat Pulldowns: Similar to pull-ups, but with resistance applied to the arms pulling down. The concentric phase involves pulling the bar towards the chest, powerfully engaging shoulder adduction and extension.
• Rows (Barbell Rows, Dumbbell Rows, Cable Rows): In these exercises, the concentric phase involves pulling a weight towards the torso. The lats engage in powerful shoulder extension and adduction to bring the elbows back and closer to the body.
• Straight-Arm Pulldowns (Lat Pullovers): This exercise primarily isolates shoulder extension and adduction with minimal elbow flexion, making it an excellent way to feel the lats concentrically working.
• Pullover Exercises (Dumbbell or Barbell Pullovers): These movements, often performed lying down, involve bringing the arms from an overhead position down towards the hips, engaging the lats in shoulder extension and adduction.

Optimizing Latissimus Dorsi Activation

To maximize the concentric function and development of the latissimus dorsi, consider these principles:

• Mind-Muscle Connection: Actively focus on "pulling with your lats" rather than just your arms. Imagine driving your elbows down and back.
• Full Range of Motion: Ensure you allow for a full stretch of the lats at the top of the movement (eccentric phase) to maximize concentric recruitment through a complete range.
• Control the Movement: Avoid momentum. The concentric phase should be deliberate and controlled, focusing on the muscle doing the work.
• Vary Grip and Angle: Different grip widths and angles can slightly shift emphasis, but the core concentric actions of adduction and extension remain central.

Conclusion

The concentric function of the latissimus dorsi is fundamental to many powerful pulling and climbing movements. By understanding its anatomical attachments and how they translate into shoulder adduction, extension, and internal rotation, fitness enthusiasts and trainers can design more effective training programs. Focusing on the deliberate shortening of the lats during the "pulling" phase of exercises is key to maximizing its strength and development, contributing to a strong, well-defined back and improved functional movement capabilities.