The Latissimus Dorsi And Teres Major Muscles

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What and where are the latissimus dorsi and teres major muscles?

Latissimus Dorsi Muscle

The latissimus dorsi is a large, powerful muscle on the back of the torso. Teres major often gets discussed along with the latissimus muscle because it’s a small muscle whose main job is to assist latissimus in some of its actions. Due to its size and power, latissimus has the potential to affect a wide range of actions in the body.

Where are the latissimus dorsi and teres major muscles located?

Generally, the latissimus dorsi covers much of the back and teres major is found just superior to the latissimus where it connects from the torso to the humerus.

Teres Major Muscle

What is the origin of latissimus dorsi and teres major?

Specifically, latissimus dorsi has a broad area of attachment that could be considered the “origin”. It attaches to the spinous processes of vertebrae T7-T12 and then via the thoracolumbar aponeurosis, a tendinous sheath of connective tissue, it connects to all of the lumbar vertebrae, the sacrum, and the posterior third of the iliac crest. Latissimus dorsi can also have an attachment on ribs 9-12 and the inferior angle of the scapula, as it moves up the torso.

Teres major originates on the inferior angle of the scapula.

What is the insertion of latissimus dorsi and teres major?

Together, latissimus dorsi and teres major go from the inferior angle of the scapula to insert on the bicipital groove of the humerus.

What actions do the latissimus dorsi and teres major muscles do?

The primary actions of both latissimus dorsi and teres major are:

  • Medial rotation of the humerus when the arm is abducted
  • Extension of the humerus
  • Adduction of the humerus

Latissimus dorsi, due to its large area of attachment, is also intimately related to maintaining balanced movement and stability of the whole shoulder complex (Hawkes et al., 2019). Similarly, healthy range of motion in latissimus is important for a balanced gait pattern during walking. Recent research suggests that there is a synergy between latissimus dorsi on one side of the body and the gluteus maximus on the opposite side of the body during each walking step we take. This synergy functions to stabilize the low back, particularly the sacroiliac joint, as we walk (Feeney et al., 2019). 

References:

Chaitow, L. and J. DeLany. 2011. Shoulder Arm and Hand. In Clinical Application of Neuromuscular Techniques. Volume 1 - The Upper Body (Second Edition).

Feeney, D.F., R.A. Capobianco, J.R. Montgomery, J. Morreale, A.M. Grabowski, and R.M. Enonka. 2018. Individuals with sacroiliac joint dysfunction display asymmetrical gait and a depressed synergy between muscles providing sacroiliac joint force closure when walking. Journal of Electromyography and Kinesiology. 43:95-103.

Hawkes, D.H., O.A. Khaiyat, A.J. Howard, G.J. Kemp, and S.P. Frostick. 2019. Patterns of muscle coordination during dynamic glenohumeral joint elevation: An EMG study. PLOS One. 14(2):1-16.