GENERAL INFORMATION
The latissimus dorsi, often referred to as the “lats,” is a large, flat muscle in the back that stretches to the sides and behind the arm. It is the most significant muscle in the upper body and is responsible for adduction, extension, and medial rotation of the shoulder. Moreover, it is also involved in the movement of the spinal column, particularly in extension and rotation.
ORIGIN OF LATISSIMUS DORSI
The latissimus dorsi originates from the spinous processes of thoracic T7-T12 from the lower six thoracic vertebrae, lumbar vertebrae, lower three to four ribs, iliac crest of the sacrum, and the thoracolumbar FasCia. Additionally, the thoracolumbar Fascia plays a crucial role in providing structural support.
INSERTION POINT
The fibres of the latissimus dorsi converge into a tendon that inserts onto the intertubercular sulcus groove of the humerus (the bicipital groove) and the floor of the bicipital groove. Consequently, this insertion allows for the effective transmission of force during shoulder and arm movements.
MAJOR ARTERIES
The main arteries supplying the latissimus dorsi are the thoracodorsal branch of the subscapular artery and the posterior intercostal arteries. Therefore, these arteries ensure adequate blood flow, which is essential for muscle function and recovery.
NEURAL INNERVATION IN LATISSIMUS DORSI
It is innervated by the thoracodorsal nerve (C6, C7, C8), a branch of the brachial plexus. Thus, proper neural input is vital for coordinated muscle activity.
TRIGGER POINT
Trigger points for the latissimus dorsi are generally found within the muscle belly along the lower and middle back and under the arm. They can be stimulated through manual pressure or massage for relief. Furthermore, a trigger point in the latissimus dorsi can cause pain and tightness in the middle to lower back, the shoulder, and the arm.
CONCENTRIC FUNCTION
The latissimus dorsi is responsible for pulling the arm downward and backwards (shoulder extension, adduction, and internal rotation). It works concentrically to extend and internally rotate the shoulder and adduct the arm towards the body. Additionally, it plays a role in movements such as pulling and reaching. This is particularly evident in activities such as swimming, rowing, and pull-ups.
ECCENTRIC FUNCTION
This muscle controls the speed and direction of the arm during forward and upward movements (shoulder flexion and abduction), such as when slowing down and lowering the arm in a controlled manner after a throw. Moreover, the latissimus dorsi works eccentrically to control the movement of the shoulder and arm during exercises such as pull-ups, rows, and pulldowns.
ISOMETRIC FUNCTION
The latissimus dorsi works isometrically to maintain proper posture while sitting or standing and keep the scapula stable during upper body exercises. When carrying heavy loads or maintaining certain positions, the latissimus dorsi works isometrically to help stabilise the shoulder joint and the spine. Consequently, it contributes significantly to overall upper body stability.
RELATED MUSCLES (SCIENTIFIC NAMES)
- Deltoid: A shoulder muscle that opposes the latissimus dorsi by facilitating arm abduction.
- Trapezius: Supports upper back, neck, and shoulder movements, synergistic with lats in some movements.
- Rhomboid Major: Retracts the scapula, working in concert with the latissimus dorsi for back stability.
- Rhomboid Minor: Smaller than the major, it assists in scapular retraction and rotation.
- Pectoralis Major: Works antagonistically to the latissimus dorsi during shoulder movements.
- Teres Major: Often works with the latissimus dorsi to medially rotate and adduct the arm.
- Teres Minor: Assists in the rotation and stabilisation of the arm, serving as a fine-tuner in movements.
- Infraspinatus: Part of the rotator cuff, helping in the lateral rotation of the arm, opposing some latissimus functions.
ANTAGONIST
- Deltoid (anterior fibres): Acts against the latissimus during arm lifting, aiding in shoulder abduction.
- Biceps Brachii: Contrasts with the lat’s action by flexing the elbow, opposing the extension.
- Brachialis: Assists the biceps in elbow flexion, working against the lat’s extension.
- Pectoralis Major (clavicular head): Opposes the downward and backward motion of the arm facilitated by the lats.
- Supraspinatus: Assists with arm lifting, counterbalancing the downward pull of the lats.
- Infraspinatus: Helps rotate the arm externally, opposing the lats’ internal rotation.
- Teres Minor: Aids in external rotation and stability, acting in opposition to the lats’ functions.
- Subscapularis: Facilitates internal rotation of the arm, directly contrasting the latissimus dorsi.
COMMON INJURIES
- Strain or tear: This is frequent in athletes, particularly from repetitive overhead activities like swimming and rowing, leading to pain and reduced mobility.
- Strains or sprains: These are common injuries resulting from improper lifting techniques or sudden, awkward movements, often leading to pain and inflammation.
- Latissimus dorsi tendonitis: Repeated shoulder motion can inflame this tendon, particularly in sports that involve throwing or swinging.
- Latissimus dorsi muscle tear: Intense physical exertion can lead to significant injury, necessitating a lengthy recovery period.
- Injury from improper weightlifting technique: Poor form during exercises like deadlifts and rows can lead to various back injuries, including the painful condition of bursitis.
EXERCISES
- Pull-ups: A fundamental exercise that engages multiple muscle groups, particularly emphasising the latissimus dorsi and improving overall upper body strength.
- Chin-ups: These are ideal for developing arm and back strength. They focus more on the biceps while still heavily involving the lats.
- Seated Rows: This exercise targets the middle back, enhancing the density of the lats and improving postural support.
- Bent-over Rows strengthen both the lats and the lower back, which is critical for enhancing core stability and power.
- Lat Pulldown: This primarily focuses on the lats, which are crucial for developing back width and enhancing shoulder health.
STRETCHES
- Overhead Lat Stretch: This stretch is excellent for increasing the range of motion in the shoulders and improving the flexibility of the latissimus dorsi.
- Underarm Shoulder Stretch: Specifically targets the lats and the posterior shoulder, easing tension and promoting mobility.
- Side Lean Lat Stretch: Focuses on stretching the lateral aspects of the lats, essential for side bending and rotational movements.
- Child’s Pose Lat Stretch: This gentle stretch benefits the lats while relieving tension in the back and shoulders, making it ideal for recovery and relaxation.
- Kneeling Lat Stretch with a Stability Ball: Provides a deep, engaging stretch, enhancing upper body flexibility and aiding in post-exercise recovery.
Professional supervision is highly recommended to prevent injuries and maximise the benefits of these stretches and exercises.