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The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the
trapezius The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports th ...
on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
and means "broadest uscleof the back", from "latissimus" ( la, broadest)' and "dorsum" ( la, back). The pair of muscles are commonly known as "lats", especially among
bodybuilder Bodybuilding is the use of progressive resistance exercise to control and develop one's muscles (muscle building) by muscle hypertrophy for aesthetic purposes. It is distinct from similar activities such as powerlifting because it focuses ...
s. The latissimus dorsi is the largest muscle in the upper body. The latissimus dorsi is responsible for
extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ext ...
, 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 shoulder joint (or glenohumeral joint from Greek ''glene'', eyeball, + -''oid'', 'form of', + Latin ''humerus'', shoulder) is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint ...
. It also has a
synergistic Synergy is an interaction or cooperation giving rise to a whole that is greater than the simple sum of its parts. The term ''synergy'' comes from the Attic Greek word συνεργία ' from ', , meaning "working together". History In Christia ...
role in extension and lateral flexion of the lumbar spine. Due to bypassing the scapulothoracic joints and attaching directly to the spine, the actions the latissimi dorsi have on moving the arms can also influence the movement of the scapulae, such as their downward rotation during a pull up.


Structure


Variations

The number of dorsal vertebrae to which it is attached varies from four to eight; the number of costal attachments varies; muscle fibers may or may not reach the crest of the ilium. A muscle slip, the axillary arch, varying from 7 to 10 cm in length, and from 5 to 15 mm in breadth, occasionally springs from the upper edge of the latissimus dorsi about the middle of the posterior fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves, to join the under surface of the tendon of the
pectoralis major The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
, the coracobrachialis, or the fascia over the
biceps brachii The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join ...
. This axillary arch crosses the axillary artery, just above the spot usually selected for the application of a ligature, and may mislead a surgeon. It is present in about 7% of the population and may be easily recognized by the transverse direction of its fibers. Guy ''et al.'' extensively described this muscular variant using MRI data and positively correlated its presence with symptoms of neurological impingement. A fibrous slip usually passes from the upper border of the tendon of the Latissimus dorsi, near its insertion, to the long head of the
triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally respon ...
. This is occasionally muscular, and is the representative of the dorsoepitrochlearis brachii of apes. This muscular form is found in ~5% of humans and is sometimes termed the latissimocondyloideus. The latissimus dorsi crosses the inferior angle of the
scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...
. A study found that, of 100 cadavers dissected: * 43% had "a substantial amount" of muscular fibers in the latissimus dorsi originating from the scapula. * 36% had few or no muscular fibers, but a "soft fibrous link" between the scapula and the latissimus dorsi * 21% had little or no connecting tissue between the two structures.


Triangles

* The lateral margin of the latissimus dorsi is separated below from the obliquus externus abdominis by a small triangular interval, the ''lumbar triangle of Petit'', the base of which is formed by the iliac crest, and its floor by the
obliquus internus abdominis The abdominal internal oblique muscle, also internal oblique muscle or interior oblique, is an abdominal muscle in the abdominal wall that lies below the external oblique muscle and just above the transverse abdominal muscle. Structure Its fib ...
. * Another triangle is situated behind the scapula. It is bounded above by the
trapezius The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports th ...
, below by the latissimus dorsi, and laterally by the vertebral border of the scapula; the floor is partly formed by the rhomboideus major. If the
scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...
is drawn forward by folding the arms across the chest, and the trunk bent forward, parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for
auscultation Auscultation (based on the Latin verb ''auscultare'' "to listen") is listening to the internal sounds of the body, usually using a stethoscope. Auscultation is performed for the purposes of examining the circulatory and respiratory systems (he ...
. The space is therefore known as the ''
triangle of auscultation The triangle of auscultation is a relative thinning of the musculature of the back, situated along the medial border of the scapula which allows for improved listening to the lungs. Boundaries It has the following boundaries: * medially, by th ...
''. *The latissimus dorsi can be remembered best for insertion as "A Miss Between Two Majors". As the latissimus dorsi inserts into the floor of the intertubercular groove of the
humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a r ...
it is surrounded by two major muscles. The teres major inserts medially on the medial lip of the intertubercular groove and the pectoralis major inserts laterally onto the lateral lip.


Nerve supply

The latissimus dorsi is innervated by the sixth, seventh, and eighth cervical nerves through the thoracodorsal (long subscapular) nerve.
Electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyo ...
suggests that it consists of six groups of muscle fibres that can be independently coordinated by the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
.


Function

The latissimus dorsi assists in depression of the arm with the teres major and
pectoralis major The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
. It adducts, extends, and internally rotates the shoulder. When the arms are in a fixed overhead position, the latissimus dorsi pulls the trunk upward and forward. It has a
synergistic Synergy is an interaction or cooperation giving rise to a whole that is greater than the simple sum of its parts. The term ''synergy'' comes from the Attic Greek word συνεργία ' from ', , meaning "working together". History In Christia ...
role in extension (posterior fibers) and lateral flexion (anterior fibers) of the lumbar spine, and assists as a muscle of both forced expiration (anterior fibers) and an accessory muscle of inspiration (posterior fibers). Most latissimus dorsi exercises concurrently recruit the teres major, posterior fibres of the
deltoid Deltoid (delta-shaped) can refer to: * The deltoid muscle, a muscle in the shoulder * Kite (geometry), also known as a deltoid, a type of quadrilateral * A deltoid curve, a three-cusped hypocycloid * A leaf shape * The deltoid tuberosity, a part o ...
, long head of the
triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally respon ...
, among numerous other stabilizing muscles. Compound exercises for the 'lats' typically involve elbow flexion and tend to recruit the
biceps brachii The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join ...
,
brachialis The brachialis (brachialis anticus), also known as the Teichmann muscle, is a muscle in the upper arm that flexes the elbow. It lies deeper than the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow ...
, and
brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...
for this function. Depending on the line of pull, the
trapezius The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports th ...
muscles can be recruited as well; horizontal pulling motions such as rows recruit both latissimus dorsi and trapezius heavily.


Training

The power/size/strength of this muscle can be trained with a variety of different exercises. Some of these include: * Vertical pulling movements such as pull-downs and pull-ups (including
chin-up A pull-up is an upper-body strength exercise. The pull-up is a closed-chain movement where the body is suspended by the hands, gripping a bar or other implement at a distance typically wider than shoulder-width, and pulled up. As this happens, t ...
s) * Horizontal pulling movements such as bent-over row,
T-bar row A surface lift is a type of cable transport for snow sports in which skiers and snowboarders remain on the ground as they are pulled uphill. While they were once prevalent, they have been overtaken in popularity by higher-capacity and higher-co ...
and other
rowing exercise In strength training, rowing (or a row, usually preceded by a qualifying adjective — for instance a ''seated row'') is an exercise where the purpose is to strengthen the muscles that draw the rower's arms toward the body (latissimus dorsi) as ...
s * Shoulder extension movements with straight arms such as straight-arm lat pulldowns and Pull-overs *
Deadlift The deadlift is a weight training exercise in which a loaded barbell or bar is lifted off the ground to the level of the hips, torso perpendicular to the floor, before being placed back on the ground. It is one of the three powerlifting exerci ...


Clinical significance

Tight latissimus dorsi has been shown to be a contributor to chronic shoulder pain and chronic back pain.Arnheim, D.D., Prentice, W.E., Principles of athletic training. 9th ed. McGraw Hill, pp 570-574, 1997. Because the latissimus dorsi connects the spine to the
humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a r ...
, tightness in this muscle can manifest as either sub-optimal
glenohumeral joint The shoulder joint (or glenohumeral joint from Greek ''glene'', eyeball, + -''oid'', 'form of', + Latin ''humerus'', shoulder) is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint ...
(shoulder) function which leads to chronic pain or tendinitis in the tendinous fasciae connecting the latissimus dorsi to the thoracic and lumbar spine.Francis, P., Applied anatomy and kinesiology, supplemental materials. KB Books., p 19-25, 1999. The latissimus dorsi is a potential source of muscle for
breast reconstruction Breast reconstruction is the surgical process of rebuilding the shape and look of a breast, most commonly in women who have had surgery to treat breast cancer. It involves using autologous tissue, prosthetic implants, or a combination of both wi ...
surgery after mastectomy (e.g. Mannu flap) or to correct pectoral hypoplastic defects such as Poland's syndrome. An absent or hypoplastic latissimus dorsi can be one of the associated symptoms of Poland's syndrome.


Cardiac support

For heart patients with low cardiac output and who are not candidates for cardiac transplantation, a procedure called ''
cardiomyoplasty Cardiomyoplasty is a surgical procedure in which healthy muscle from another part of the body is wrapped around the heart to provide support for the failing heart. Most often the latissimus dorsi muscle is used for this purpose. A special pacemake ...
'' may support the failing heart. This procedure involves wrapping the latissimus dorsi muscles around the heart and electrostimulating them in synchrony with ventricular systole.


Injury

Injuries to the latissimus dorsi are rare. They occur disproportionately in baseball pitchers. Diagnosis can be achieved by visualization of the muscle and movement testing. MRI of the shoulder girdle will confirm the diagnosis. Muscle belly injuries are treated with rehabilitation while tendon avulsion injuries can be treated surgically, or with rehab. Regardless of treatment, patients tend to return to play without any functional losses.


Additional images

File:Latissimus dorsi muscle animation.gif, Position of the latissimus dorsi muscle (shown in red). Animation. File:Latissimus dorsi muscle animation3.gif, Animation. Rib cage is not shown, except for 10th rib, 11th rib and 12th rib. File:LumbarTriangle.jpg, Lumbar triangle File:Slide9111.JPG, Latissimus dorsi File:2019-05-24 Budapest Cup training pommel horse (Martin Rulsch) 466.jpg, Clearly visible ''latissimus dorsi muscle'' of an
artistic gymnast Artistic gymnastics is a discipline of gymnastics in which athletes perform short routines on different apparatuses. The sport is governed by the Fédération Internationale de Gymnastique (FIG), which designs the Code of Points and regulates ...
on
pommel horse The pommel horse is an artistic gymnastics apparatus. Traditionally, it is used by only male gymnasts. Originally made of a metal frame with a wooden body and a leather cover, the modern pommel horse has a metal body covered with foam rubber and ...
. File:Deutsche Jugendmeisterschaften Gerätturnen männlich Training at Internationales Deutsches Turnfest Berlin 2017 (Martin Rulsch) 0857.jpg,
Contraction Contraction may refer to: Linguistics * Contraction (grammar), a shortened word * Poetic contraction, omission of letters for poetic reasons * Elision, omission of sounds ** Syncope (phonology), omission of sounds in a word * Synalepha, merged ...
of the ''latissimus dorsi muscle'' of another artistic gymnast on still rings.


See also

*
Muscle energy technique Muscle Energy Techniques (METs) describes a broad class of manual therapy techniques directed at improving musculoskeletal function or joint function, and improving pain. METs are commonly used by manual therapists, physical therapists, occupationa ...
s


References


External links

* - "Superficial layer of the extrinsic muscles of the back." * {{DEFAULTSORT:Latissimus Dorsi Muscle Muscles of the upper limb Shoulder adductors Shoulder extensors Shoulder medial rotators Shoulder flexors Spine lateral flexors