Latissimus dorsi muscle
Encyclopedia
The latissimus dorsi meaning 'broadest muscle of the back' (Latin
latus meaning 'broad', latissimus meaning 'broadest' and dorsum meaning the back), is the larger, flat, dorso-lateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.
The latissimus dorsi is responsible for extension
, adduction
, transverse extension also known as horizontal abduction, flexion from an extended position, and (medial) internal rotation
of the shoulder joint. It also has a synergistic role in extension and lateral flexion of the lumbar spine.
Due to bypassing the scapulothoracic joint and attaching directly to the spine, the actions the lat has on moving the arm can also influence the movement of the scapulae, such as their downward rotation during a pull up.
A muscular 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 coracobrachialis, or the fascia over the biceps brachii. 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% os 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. This is occasionally muscular, and is the representative of the dorsoepitrochlearis brachii of ape
s.
(long subscapular) nerve. Electromyography
suggests that it consists of six groups of muscle fibres that can be independently coordinated by the central nervous system
.
with the following exercises:
Weight training must be carefully controlled due to the importance of the muscle.
Most latissimus dorsi exercises concurrently recruit the teres major, posterior fibers of the deltoid
, long head of the triceps brachii, among numerous other stabilizing muscles. Compound exercises for the 'lats' typically involve elbow flexion and tend to recruit the biceps brachii, brachialis, and brachioradialis
for this function. Depending on the line of pull, the trapezius muscles can be recruited as well; horizontal pulling motions such as rows recruit both latissimus dorsi and trapezius heavily.
Tight latissimus dorsi has been shown to be one cause of chronic shoulder pain and chronic back pain. Because the latissimus dorsi connects the spine to the humerus
, tightness in this muscle can manifest as either sub-optimal glenohumeral joint
(shoulder) function which leads to chronic pain or tendinitis in the tendinous fasciae connecting the latissimus dorsi to the thoracic and lumbar spine.
may support the failing heart. This procedure involves wrapping the latissimus dorsi muscles around the heart and electrostimulating them in synchrony with ventricular systole.
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
latus meaning 'broad', latissimus meaning 'broadest' and dorsum meaning the back), is the larger, flat, dorso-lateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.
The latissimus dorsi is responsible for extension
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
, adduction
Adduction
Adduction is a movement which brings a part of the anatomy closer to the middle sagittal plane of the body. It is opposed to abduction.-Upper limb:* of arm at shoulder ** Subscapularis** Teres major** Pectoralis major** Infraspinatus...
, transverse extension also known as horizontal abduction, flexion from an extended position, and (medial) internal rotation
Internal rotation
In anatomy, internal rotation is rotation towards the center of the body.The muscles of internal rotation include:* of arm/humerus at shoulder** Deltoid muscle** Subscapularis** Teres major** Latissimus dorsi...
of the shoulder joint. It also has a synergistic role in extension and lateral flexion of the lumbar spine.
Due to bypassing the scapulothoracic joint and attaching directly to the spine, the actions the lat has on moving the arm can also influence the movement of the scapulae, such as their downward rotation during a pull up.
Variations
The number of dorsal vertebræ to which it is attached vary from four to eight; the number of costal attachments varies; muscle fibers may or may not reach the crest of the ilium.A muscular 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 coracobrachialis, or the fascia over the biceps brachii. This axillary arch crosses the axillary artery
Axillary artery
In human anatomy, the axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla and the upper limb...
, just above the spot usually selected for the application of a ligature, and may mislead a surgeon. It is present in about 7% os 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. This is occasionally muscular, and is the representative of the dorsoepitrochlearis brachii of ape
Ape
Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...
s.
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 crestIliac crest-External links: - "Superficial muscles of the gluteal region and posterior thigh." - "Anterior Abdominal Wall: Osteology and Surface Anatomy " - "The Back, Posterior View" * *...
, and its floor by the obliquus internus abdominis.
- Another triangle is situated behind the scapula. It is bounded above by the trapezius, 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 scapulaScapulaIn anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
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 auscultationAuscultationAuscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
. The space is therefore known as the triangle of auscultation.
- The Latissimus Dorsi can be remembered best for insertion as "The Lady Between Two Majors". As the Latissimus Dorsi inserts into the floor of the intertubercular groove of the humerusHumerusThe humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
it is surrounded by two major muscles. The Teres Major inserts medially on the medial lip of the intertubercular groove and laterally the Pectoralis Major inserts into the lateral lip.
Innervation
The Latissimus dorsi is supplied by the sixth, seventh, and eighth cervical nerves through the Thoracodorsal (long scapular)Thoracodorsal nerve
The thoracodorsal nerve is a nerve present in humans and other animals. It is also known as the middle subscapular nerve or the long subscapular nerve. It supplies the latissimus dorsi muscle....
(long subscapular) nerve. Electromyography
Electromyography
Electromyography 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 electromyograph detects the electrical potential generated by muscle...
suggests that it consists of six groups of muscle fibres that can be independently coordinated by the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
.
Training
To increase the power of this muscle it should be trainedWeight training
Weight training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the weight force of gravity to oppose the force generated by muscle through concentric or eccentric contraction...
with the following exercises:
- deadliftDeadliftThe deadlift is a weight training exercise where a loaded barbell is lifted off the ground from a stabilized, bent over position. It is one of the three canonical powerlifting exercises, along with the squat and bench press.-Overview:...
- chin-upChin-upThe chin-up is a strength training exercise. The verb chinning means to do them. People frequently do this exercise with the intention of strengthening muscles such as the latissimus dorsi and biceps, which extend the shoulder and flex the elbow, respectively.It is a form of pull-up in which the...
and pull-upPull-up (exercise)A pull-up is an upper body compound pulling exercise where the body is suspended by the arms, gripping something, and pulled up with muscular effort... - pull-downPulldown exerciseThe pulldown exercise or the cable lat pulldown is a strength training exercise designed to develop the latissimus dorsi muscle. It performs the functions of downward rotation and depression of the scapulae combined with adduction and extension of the shoulder joint.-Muscles:The standard pulldown...
- bent-over rowBent-over rowA bent-over row is a weight training exercise that targets a variety of back muscles. Which ones are targeted varies on form. The bent over row is often used for both bodybuilding and powerlifting...
- pull-over
- dumbbell-rowsRowing exerciseIn strength training, rowing is a form of muscular resistance training exercise that shares many characteristics of rowing a boat without involving water or a boat...
- T-bar row
Weight training must be carefully controlled due to the importance of the muscle.
Most latissimus dorsi exercises concurrently recruit the teres major, posterior fibers of the deltoid
Deltoid muscle
In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the central...
, long head of the triceps brachii, among numerous other stabilizing muscles. Compound exercises for the 'lats' typically involve elbow flexion and tend to recruit the biceps brachii, brachialis, and brachioradialis
Brachioradialis
Brachioradialis is a muscle of the forearm that acts to flex the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm...
for this function. Depending on the line of pull, the trapezius muscles can be recruited as well; horizontal pulling motions such as rows recruit both latissimus dorsi and trapezius heavily.
Tight latissimus dorsi has been shown to be one cause of chronic shoulder pain and chronic back pain. Because the latissimus dorsi connects the spine to the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, tightness in this muscle can manifest as either sub-optimal glenohumeral joint
Glenohumeral joint
The glenohumeral joint, or shoulder joint, is a multiaxial synovial ball and socket joint and involves articulation between the glenoid fossa of the scapula and the head of the humerus...
(shoulder) function which leads to chronic pain or tendinitis in the tendinous fasciae connecting the latissimus dorsi to the thoracic and lumbar spine.
Cardiac support
For heart patients with low cardiac output and who are not candidates for cardiac transplantation, a procedure called cardiomyoplastyCardiomyoplasty
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 pacemaker is implanted to make the skeletal muscle contract....
may support the failing heart. This procedure involves wrapping the latissimus dorsi muscles around the heart and electrostimulating them in synchrony with ventricular systole.