Muscle Minute TUESDAY – Meet the Latissimus Dorsi

One of the largest muscles of the back, the latissimus dorsi is uniquely positioned, twisting its way from the posterior aspect of the trunk to the front of the shoulder. It is a muscle that is often targeted for hypertrophy as it gives one a triangular appearance and is often considered a powerful adductor and extender of the arm. But it’s connections and influence is far greater than that. Let’s dive in…

Origin	T7-L5 spinous process, thoracolumbar fascia, iliac crest, inferior angle of scapula
Insertion	floor of the intertubercular groove (humerus)
Action	adduction, extension and IR of the arm, lumbar extension AND rotation of the trunk
Innervation	thoracodorsal n. (C6, C7, C8)
Antagonists	lower trapezius

The Real World Latissimus Dorsi

There are several things about this muscle that are important to note:

Its connection to the thoracolumbar fascia makes it a powerful lumbar extender. More importantly, tightness of this muscle will cause lumbar hyperextension at rest.
It intersects with its antagonist, the lower trapezius, in an area known as a myofascial super highway from T7-T12. Usually a muscle’s antagonist is on the opposite side of the body, but this antagonist sits directly superior. Myofascial restrictions in this area may limit thoracic side bending, the primary motion occurring at these segments.
It inserts at the floor of the intertubercular groove, in between two majors (pec major and teres major), making it a powerful internal rotator of the shoulder. Just like these two synergists, if it becomes tight, it will position the humerus in internal rotation. Myofascial restriction in the posterior axillary region will limit thoracic rotation.
This muscle is rarely injured but is often the cause of injury. Rotator cuff impingement and lower back pain from hyperextension are two of the most common overuse injuries that are associated with tight latissimus dorsi.
Common body building programs will use a “back and bicep” and “chest and tricep” day split with the latissimus dorsi targeted on “back day”. But back day should include more than the latissimus dorsi. Though it gives the back shape, latissimus dorsi creates a kyphosis, just like the chest muscles. In order to achieve the desired balance, “back day” must target the muscles that reduce thoracic kyphosis: lower trapezius, rhomboids and mid trap.

Conventional thinking says: Strengthen the lats to get a nice wide back and triangular appearance.

Real World Thinking says: It’s equally (if not more) important to make sure this muscle is flexible as tightness will create an increase in thoracic kyphosis, forward shoulder and lumbar extension, causing rotator cuff impingement and lower back pain.

Because nobody has time to be in pain.

Until next time…