Latissimus dorsi

Function

Where the muscle sits

The latissimus dorsi is a broad, triangular muscle on the lower part of the back⁸. No other muscle of the upper trunk is larger¹. Many muscles cross the shoulder and move the humerus (upper arm bone)⁸. Two of them are axial muscles, meaning muscles based on the trunk rather than on the limbs or shoulder blade⁸. They are this muscle and the pectoralis major, the large chest muscle⁸.

Four panels of the shoulder. The pectoralis major fans across the chest to the upper arm, and the latissimus dorsi sweeps from the lower back and flank up to the arm. A posterior view shows the deltoid capping the shoulder over the latissimus dorsi, and two deep views show the rotator cuff muscles, teres major and the heads of the triceps. — Muscles that move the upper armBetts JG, Young KA, Wise JA, et al. Anatomy and Physiology, Figure 11.23. OpenStax, 2013. Access for free at openstax.org. (source, CC BY 4.0). Resized to 1400 pixels wide.

The muscle starts from a wide area^1,2:

the spiny bumps on the backs of the lower six thoracic (chest-level) vertebrae (spine bones)^1,2;
the lumbar (lower back) spine^1,2;
the thoracolumbar fascia, a sheet of tough tissue over the lower back^1,2;
the lowest three to four ribs^1,2;
the iliac crest, the top rim of the pelvis^1,2;
the lower tip of the scapula (shoulder blade)^1,2.

The muscle ends in a tendon (a tough cord joining muscle to bone) on the upper arm bone^1,2. The tendon attaches in the floor of a groove there, called the intertubercular or bicipital groove^1,2. The thoracodorsal nerve supplies the muscle^2,4.

What it moves

At the shoulder, the muscle does three things^1,2,3:

Action	What the arm does
Extension	Moves the arm backward^1,2,3
Adduction	Moves down and in, toward the body^1,2,3
Internal rotation	Turns inward^1,2,3

It adds little to abduction, which means lifting the arm out to the side¹. Its activity is also out of step with the main muscles that lift the arm this way¹. The teres major, a thick shoulder muscle from the shoulder blade to the upper arm bone, works with it to make the same three movements⁴.

How it works in a throw

The first muscle-activity study of pitching showed the muscle working in two ways⁴. In these pitchers, the muscle first works while lengthening to slow the arm as it moves back, then shortens to pull the arm forward⁴. Working while lengthening is called an eccentric contraction; working while shortening is a concentric one⁴. The switch happens as the throw moves from late cocking, with the arm drawn back, into acceleration⁴.

Whether it turns the trunk

Whether the muscle helps twist the spine is disputed⁶. One group argued that it is built to move the arm⁶. In their view, its part in bracing the joints between spine and pelvis through the thoracolumbar fascia is trivial⁶. The background of a separate trunk-rotation study describes it as acting on the same side as the turn⁹. In 24 young men twisting against a machine, the external oblique, a side abdominal muscle, was more active than this muscle¹⁰.

Breakdown

Who tears the muscle

Injuries to this muscle and the teres major are uncommon⁴. They happen in high-level athletes who throw overhead again and again⁴. Most reported cases are in professional baseball pitchers². Cases have also been reported in these groups²:

weight lifters and CrossFit athletes²;
water skiers and steer wrestlers²;
rock climbers and track athletes².

In people who do not pitch, two kinds of event are the typical cause². One is pulling the arm down and forward hard against resistance². The other is the arm being forced suddenly back, or too far out to the side².

When in the throw it happens

In pitching, injury most often happens as late cocking turns into acceleration⁴. That is the moment the muscle switches from lengthening to shortening⁴. How much a pitcher throws is also linked to tears¹¹. In most periods studied, games with more innings and more batters faced went with more tears later¹¹. Being a starting pitcher was also linked to a higher risk¹¹.

What kinds of tear there are

Four main types of rupture, or tear, have been described²:

A tear or avulsion of the tendon alone, where avulsion means the tendon pulls off the bone².
Combined injuries, with the pectoralis major, teres major or rotator cuff (four muscles that steady the shoulder joint) also hurt².
A strain where muscle meets tendon².
A strain within the muscle itself, the least common type².

A review of injured professional players says tears are most often reported in two places⁴. One is where muscle turns into tendon, and the other is where the tendon meets bone⁴.

Recovery

How the muscle adapts to training

In two studies, the muscle or its fibres grew over a period of training^5,12. In one study, 18 healthy young adults did eight weeks of resistance training that got harder over time⁵. They had not trained with weights regularly for at least two years before, and each ate either a normal or a high protein diet⁵. Across both diet groups, strength rose, and so did cross-sectional area (the size of a slice cut across) for the whole muscle and single fibres⁵. These are changes measured before and after training, and everyone in the study trained⁵.

In the same study, the mix of fibre types also changed⁵. Myosin is the protein in muscle fibres that makes them contract; its forms are used to sort fibres into types. Fibres shifted from making type 2X myosin toward type 2A myosin (both fast types)⁵. In a separate study, nine people did hard canoeing training for nine weeks¹². Afterwards, the average size of their type II fibres in this muscle was 82% greater¹².

How players return after a tear

Most of the studies of return after a tear below are in professional baseball players^4,13,14. In 120 pitchers with a tear of this muscle or the teres major, 75% returned to play¹³. The rate was the same with or without surgery¹³. On average, the time back to the same level was much longer with surgery than without¹³:

Group	Average days to return to the same level
Without surgery	About 170, with wide variation¹³
With surgery	About 406, with wide variation¹³

The two groups may not be directly comparable⁴. In one review, the pitchers who had surgery had first tried non-surgical care without success⁴. A systematic review of 159 players found similar return rates with and without surgery⁴. It judged the evidence too mixed and too weak to compare the two approaches⁴.

Smaller studies show the range of outcomes¹⁴:

A later study summarises 16 players managed without surgery: 15 returned to the same or a higher level, after about 82 days on average¹⁴.
In the same group, 9 injuries ended the season, and 5 of those were full avulsions¹⁴.
In 20 men with a tear, 80% of them baseball pitchers, each professional baseball player in the group returned, after 8.7 months on average¹⁴.
In that group, some needed surgery after non-surgical care failed¹⁴.

Connections

The teres major beside it

The teres major works with the latissimus dorsi to pull the arm in, back and inward⁴. In a study of cadavers (bodies donated for study), some teres major fibres attached straight into this tendon in 15 of 18 bodies⁴. Three patterns of attachment are described, from fully separate to fully combined^1,15. How common each pattern is differs between reports^1,15.

The back sheet and the opposite hip

The muscle helps form the thoracolumbar fascia⁶. The outer part of the fascia’s back layer is mostly made of flat tendon sheets from two muscles⁶. These are this muscle and the serratus posterior inferior, a muscle of the back⁶. In nine cadavers, the muscle merged with the external oblique at about the level of the 9th to 11th ribs¹⁶. In some cadavers and scans, the external oblique’s covering joined the covering of this muscle first¹⁷.

The muscle may also tense the thoracolumbar fascia, and that tension may reach across to the opposite side of the pelvis^6,18. In 10 donor bodies, a simulated muscle pull moved the fascia’s back layer, suggesting this muscle, among others, would tense its outer part in life¹⁸. Below about the fourth lumbar vertebra, tension in this layer crossed to the other side¹⁸. It has been proposed that this muscle and the opposite gluteus maximus, the main buttock muscle, both tense the fascia⁶. That would give a route for force between the pelvis and the trunk⁶.

In 54 runners and inactive people, tensing this muscle stiffened the lower back¹⁹. It also changed the resting position and stiffness of the opposite hip¹⁹. A systematic review found moderate evidence for force passing at one of two links in this back chain⁷. The chain runs from this muscle to the opposite gluteus maximus, then to the vastus lateralis on the outer thigh⁷. The review noted that differing methods made the studies hard to compare⁷.

A chain down the back of the arm

A review of dissection studies places the muscle in a chain of connected tissue down the back of the arm²⁰. The chain runs to the triceps behind the upper arm, the anconeus at the elbow, and a wrist muscle, the extensor carpi ulnaris²⁰. Whether this chain matters for moving force is not yet known²⁰.

Exercises that work the muscle

Studies of muscle activity show this muscle at work in several exercises^3,21,22:

Exercise	What studies found for this muscle
Bent-over row	A review names it one of the row’s main targets³
Bent-over row	One unrepeated study of 20 men found more activity with a wide grip than a narrow one³
Inverted row	In 7 men, highest of three rows tested, including the standing bent-over row²³
Bench press	In 28 men, activity was similar across grip widths²⁴
Dead hang	In 17 climbers, less active with straight arms than with bent elbows²²
Farmer’s carry	In one study, more active than in the yoke walk²¹
Plank	In 18 adults, face-down (prone) exercises such as the plank: about 110–160% more active than the crunch²⁵
Overhead press	In 12 men, more active with an unstable “Earthquake” bar carrying kettlebells hung from elastic bands than a stable barbell²⁶

For the bent-over row, a 2026 review found two studies on how technique changes muscle activity³. A review of bench press studies notes an earlier suggestion that this muscle may be a main mover in the lift²⁷. In the farmer’s carry study, activity averaged well above the level of a maximal test contraction, at 152% and 169% on the two sides²¹. In the same 18 adults, face-down and side-lying exercises on the toes, rather than the knees, raised the activity of several muscles, including this one²⁵.