Maximus Gage
The latissimus dorsi, commonly referred to as the 'lats', are the largest muscles in the upper half of the body. They are relatively thin and cover almost all back muscles at the posterior trunk, except the trapezius. Above the lats are the trapezius, levator scapulae, and rhomboid muscles. Together, these muscles form the superficial layer of extrinsic back muscles, which are responsible for scapular motion. The trapezius muscle, for example, partly covers the latissimus dorsi and is involved in pulling the shoulder girdle down and assisting in side bending.
| Characteristics | Values |
|---|---|
| Common name | Lats |
| Scientific name | Latissimus dorsi |
| Location | Back |
| Description | Broad, flat muscle that covers almost all back muscles at the posterior trunk |
| Function | Extension, adduction, transverse extension, flexion from an extended position, and (medial) internal rotation of the shoulder joint |
| Innervation | Sixth, seventh, and eighth cervical nerves through the thoracodorsal nerve |
| Blood supply | Thoracodorsal artery |
| Nerve supply | Long scapular nerve |
| Associated pathologies | Chronic shoulder pain, chronic back pain, posterior shoulder dislocations |
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What You'll Learn
The latissimus dorsi is the widest muscle in the human body
The latissimus dorsi muscle, commonly known as the "lats" muscle, is the widest muscle in the human body. It is a large, flat muscle that covers almost all back muscles at the posterior trunk, except the trapezius. The latissimus dorsi is relatively thin and originates from six vertebrae in the lower middle part of the back and the last three or four ribs. Its origin also includes the connective tissue called thoracolumbar fascia, located in the lower back, and a small portion of the bottom angle of the shoulder blade.
The primary function of the latissimus dorsi is related to the upper extremity, but it is also considered a respiratory accessory muscle. It assists in depression of the arm and has a role in extension, adduction, transverse extension, flexion from an extended position, and medial internal rotation of the shoulder joint. The latissimus dorsi also assists in side bending, or lateral flexion, and is one of the main stabilizers of the spine, helping with arching the spine and tilting the pelvis anteriorly.
The latissimus dorsi muscle is an important muscle for activities such as rowing, swimming, and chopping. It is active during violent expiration and can be felt pressing forcibly inward during a cough or sneeze. The muscle also assists in holding the scapula against the thorax during upper limb movements. In people with paralysis of the lower body, the latissimus dorsi can pull the trunk forward relative to the arms, with a lifting of the pelvis.
A tight latissimus dorsi can contribute to chronic shoulder and back pain. This is due to the muscle's connection between the spine and the humerus, with tightness leading to sub-optimal glenohumeral joint function and tendinitis in the connecting fasciae. For individuals with low back pain, assessing the length and flexibility of the latissimus dorsi is important as alterations in this muscle can impact movement patterns and postures, potentially exacerbating the pain.
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It assists in depression of the arm with the teres major and pectoralis major
The latissimus dorsi, commonly known as "lats", are large, flat muscles on the back that stretch to the sides, behind the arms. They are the largest muscles in the upper half of the body. The latissimus dorsi is involved in several functions, including depression of the arm, which it does with the help of the teres major and pectoralis major muscles.
The teres major is one of four rotator cuff muscles that assist in many shoulder pathologies. It acts in synergy with the latissimus dorsi to extend, adduct, and internally rotate the shoulder. The teres major also assists the rotator cuff group in stabilizing the shoulder joint. Its main actions include adduction and internal rotation of the humerus, as well as scapular protraction.
The pectoralis major is a large muscle located in the pectoral girdle region. It can be subdivided into its clavicular head and its sternocostal head. The clavicular portion flexes the humerus, while the sternocostal head adducts and medially rotates the humerus. The pectoralis major also acts to adduct the humeral head.
Together, the latissimus dorsi, teres major, and pectoralis major muscles work to adduct, medially rotate, and extend the arm at the glenohumeral joint. They also collaborate during the extension of the humerus. The actions of these muscles on moving the arms can also influence the movement of the scapulae, such as their downward rotation.
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It's an accessory muscle for inspiration and expiration
The latissimus dorsi muscle, commonly known as the "lats", is a large, flat muscle on the back that stretches to the sides and behind the arm. It is the largest muscle in the upper half of the body. Beginning below the shoulder blades, it extends to the spine in the lower back.
The latissimus dorsi is an accessory muscle for inspiration and expiration. Inspiration, or inhalation, is an active process that involves the contraction of muscles to increase the volume of the thoracic cavity, thereby producing lung expansion. The diaphragm is the main inspiratory muscle, but the latissimus dorsi assists in this process by lifting the ribs to increase space for air in the lungs.
Expiration, or exhalation, is typically a passive process that occurs due to the elastic recoil of the lungs and muscles. However, during certain activities such as exercise or playing a musical instrument, expiration can become an active process. The latissimus dorsi is involved in violent expiration, as it attaches to the ribs and compresses the thorax and abdomen during actions like coughing or sneezing.
The latissimus dorsi also has a synergistic role in the extension and lateral flexion of the lumbar spine. It assists in the depression of the arm and internally rotates the shoulder. When the arms are in a fixed overhead position, it pulls the trunk upward and forward, as seen in climbing or performing a chin-up.
Overall, the latissimus dorsi plays a significant role in both inspiration and expiration, contributing to the complex process of respiration and influencing upper body movements.
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Tight lats can cause chronic shoulder and back pain
The latissimus dorsi, commonly known as the "lats", are large, flat muscles on the back that stretch to the sides and behind the arms. They are the largest muscles in the upper half of the body and play a role in upper body functioning, including arm movement, shoulder joint movement, and spinal extension and lateral flexion.
Additionally, tight lats are often associated with weak back and shoulder muscles, including the deltoids, rhomboids, and trapezius muscles. This combination of tight lats and weak surrounding muscles can lead to neck and shoulder pain, as well as restricted shoulder mobility and stability.
To address tight lats and the associated pain, it is recommended to release the tightness through foam rolling, stretching, and upper-body mobility drills. Strengthening the surrounding muscles through strength training is also beneficial. A simple test to check for tight lats is to lie on the floor with your hands above your head; if your hands don't touch the ground, your lats may be tight.
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Lats are controlled by the long scapular nerve
The latissimus dorsi, commonly known as the "lats", is a broad, flat muscle that covers almost all back muscles at the posterior trunk, except the trapezius. The lats are the widest muscles in the human body. They start below the shoulder blades and extend to the spine in the lower back. The muscle is responsible for extension, adduction, transverse extension (also known as horizontal abduction or horizontal extension), flexion from an extended position, and medial internal rotation of the shoulder joint. The lats also have a synergistic role in the extension and lateral flexion of the lumbar spine.
The lats are controlled by the long scapular nerve, also known as the thoracodorsal nerve. The nerve innervates the latissimus dorsi muscle on its deep surface. The thoracodorsal nerve is a branch of the brachial plexus, which arises from the sixth, seventh, and eighth cervical nerves. The nerve enters the muscle on its costal surface, medial to the lateral border, and a few centimetres from the subscapular artery.
The latissimus dorsi is an extrinsic muscle of the shoulder. It originates from the spinous processes of T7-T12, the iliac crest, the thoracolumbar fascia, and the inferior three ribs. The fibres converge into a tendon that attaches to the intertubercular sulcus of the humerus.
The lats have several important functions. Firstly, they assist in depression of the arm, along with the teres major and pectoralis major muscles. Secondly, they play a role in adduction, extension, and internal rotation of the shoulder. Thirdly, when the arms are in a fixed overhead position, the lats help to pull the trunk upward and forward, as in climbing or performing a chin-up. Additionally, the lats assist in forced expiration by compressing the rib cage, making them active during coughing or sneezing.
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Frequently asked questions
The teres major muscle lies superior to the latissimus dorsi (lats). The latissimus dorsi is the widest muscle in the human body, covering almost all back muscles at the posterior trunk except the trapezius.
The lats have several functions, including:
- Extension, adduction, and internal rotation of the shoulder joint
- Assisting in the act of side bending (lateral flexion)
- Arching the spine (hyperextension)
- Tilting the pelvis anteriorly
- Helping with the breathing process by enhancing the movements of the trunk during inhalation and exhalation
Some exercises that use the lats extensively include chin-ups, rock climbing, and swimming. A stretch for the lats involves standing tall with your back straight and hands above your head, then gently leaning to one side until you feel a stretch in your upper back and shoulder. Hold for 5 seconds, then repeat on the other side.
If you have an injury to your lats, such as a strain, pull, or tear, you should see a healthcare provider. Treatment for a latissimus problem typically includes rest, anti-inflammatory medication, moist heat, and sometimes muscle relaxers. Physical therapy is often recommended to help regain full function.
