Description[edit | edit source] Show
The latissimus dorsi muscle is a broad, flat muscle that occupies the majority of the lower posterior thorax. The muscle's primary function is of the upper extremity but is also considered to be a respiratory accessory muscle.[1]
Anatomy[edit | edit source]The muscle has attachments to
The muscle fibers are situated in various orientations with the uppermost fibers almost horizontally oriented and the lower fibers much more vertically oriented on the thorax.
Image: Latissimus dorsi muscle (highlighted in green) - posterior view [4] Nerve and Blood Supply Thoracodorsal nerve (C6 – C8)[5] from the posterior cord of the brachial plexus, which enters the muscle on its deep surface.[6] The skin covering the latissimus dorsi muscle is supplied by roots T4 to T12, inclusive by both ventral and dorsal rami, as well as the dorsal rami of L1 to L3.[6] Action[edit | edit source]Latissimus dorsi works collaboratively with the teres major and pectoralis major to perform actions of the upper extremity. Together, these muscles will work to adduct, medially rotate and extend the arm at the glenohumeral joint. Latissimus dorsi, along with teres major and the sternal head of pectoralis major, is also active in the extension of the humerus. Extension and adduction will be strongest when the motion is started from a position of partial flexion or abduction or a combination of the two motions. The muscle is also active in moving the trunk forward and upward when the upper extremities are fixed overhead, as in climbing or performing an activity such as a chin up. Research has also demonstrated that the latissimus dorsi is also active during deep inspiration and with forceful respiratory functions such as coughing and sneezing.[1] Functional Activity[edit | edit source]Latissmus dorsi is a climbing muscle. With the arms fixed above the head, it can raise the trunk upwards, together with the help of pectoralis major. It is an important muscle in rowing, swimming (especially during the downstroke) and chopping. The muscle is also active in violent expiration, as it attaches to the ribs. During a cough or sneeze, the muscle can be felt pressing forcibly inward, as it acts to compress the thorax and abdomen.[6] The muscle assists in holding the scapula against the thorax during upper limb movements. The attachment of the muscle to the inferior angle of the scapula allows this. In activities such as walking with crutches, where the humerus becomes the fixed point when standing, latissimus dorsi has the ability to pull the trunk forwards relative to the arms. With this action there is also a lifting of the pelvis. In people with paralysis of the lower half of the body, the fact that latissimus dorsi attaches to the pelvis and the fact that it is still innervated, enables the person to produce movement of the pelvis and trunk. As a result of this, people wearing calipers and using crutches can achieve a modified gait by fixing the arms and hitching the hips by alternative contraction of each latissimus dorsi.[6] Due to this muscle's broad attachment on the spinous processes, ongoing research is looking at what, if any, role the muscle plays in trunk movement. Currently, the evidence is mixed on how much influence this muscle has on spine extension, lateral flexion, or rotation[1]. Physiotherapy[edit | edit source]Latissimus dorsi may be implicated in patients with restrictions of motion of abduction, flexion and lateral rotation. Assessment of this muscle is crucial for patients with upper extremity pathology. Proper function and coordination with the teres major and pectoralis major muscles are essential for smooth and fluid movements of the upper extremity. The latissimus dorsi are an essential part of the back. Effectively training the lats gives all sorts of excellent benefits. These aren't just benefits for bodybuilders, who should know the advantages of training their back muscles, but they are benefits for everyday movement and everyday life, too. An example of a strength exercise is the chin up or beginners chair assisted chin up. For patients with low back pain, it is important to assess the length and flexibility of the latissimus dorsi due to the attachments on the spine and pelvis. A decrease in length or an increase in stiffness of this muscle can lead to alterations in movement patterns and/or postures which can exacerbate low back pain.[1] Palpation[edit | edit source]The lateral aspect of the latissimus dorsi muscle builds the posterior border of the axilla. It is felt to contract during resisted adduction of the arm. Its insertion lies anteriorly at the crest of the lesser tuberosity. By asking a patient to raise his/her arm to 90% flexion and hold it steady against an upwardly directed pressure, the latissimus dorsi muscle can be made to stand out relative to the thorax. Clinicians can palpate for a muscle contraction by holding the posterior axillary fold between the finger and thumb and asking the patient to cough. Muscle Testing[edit | edit source]Muscle testing of the latissimus dorsi muscle occurs in a prone position with the arm adducted and fully extended with the elbow extended. Resistance is applied to the forearm into the abduction and slight flexion. If the latissimus dorsi is short or tight, the back will extend and rotate as the upper extremity is flexed into an overhead position as in reaching for an object on a high shelf. The accommodation of extension and rotation of the spine allows for the achievement of the overhead position of the upper extremity.[1] Muscle Flexibility and Manual Therapy[edit | edit source][9]
References[edit | edit source]
What is the action of the latissimus dorsi?Latissimus dorsi works collaboratively with the teres major and pectoralis major to perform actions of the upper extremity. Together, these muscles will work to adduct, medially rotate, and extend the arm at the glenohumeral joint.
What is the action of latissimus dorsi quizlet?what are the functions/actions of the latissimus dorsi? extends, adducts and medially rotates the shoulder.
What two movements are produced by the contraction of the latissimus dorsi?The latissimus dorsi is responsible for two primary movements at the shoulder joint, extension and adduction. Extension happens when you raise your arm in front or behind you; adduction happens when your arm is out to your side and you lower it.
Which of the following actions is not the actions of latissimus dorsi?Lateral (external) rotation of the arm at the shoulder is NOT an action created by the latissimus dorsi as this action is caused by the teres minor muscle.
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