Pull-up for Activation
By
Mark “The Student” Harmon
While most muscle activation occurs in the upper and middle back during
pull-ups, it’s also important to realize that the shoulders, elbow flexors and
chest are involved in this movement to a certain degree. The largest of the
active muscle groups is the latissimus dorsi, more commonly known as the
lats. They’re located in the middle of the back and not the upper. The fibers of
the latissimus dorsi muscle extend from a lower (inferior) position of the
thoracic vertebrae, the iliac crest of the hip, to converge much like a fan on
the upper (superior) portion of the humerus bone of the upper arm near the
shoulder.
The primary function of all of the fibers acting together is to extend the
humerus (pulling the upper arm backward), adduct the humerus (bring the arm
towards the center of the body) and rotate the shoulders inward, which is
referred to as medial rotation. The lower part of the latissimus dorsi muscle
has more of a direct line of pull when the shoulder is flexed and the arm is
raised to a position that is about 30 degrees above a line parallel to the
floor.
The middle fibers of the muscle have direct pull with the hands and arms,
working at mid-chest level. The upper fibers are best activated with the
shoulders a little above shoulder height. Working with the arms directly over
the head tends to activate the middle and upper parts of the muscle more
effectively. Performing pull-ups activates all areas of the latissumus.
The width of the upper back immediately under the arm - in the region of the
axilla, or better known as the “armpit” - is generated by the teres major
muscle. Don’t confuse this with the latissumus muscle. The teres muscle begins
on the inferior angle of the scapula - better known as the shoulder blade - but
it attaches high into the same region of the humerus bone of the arm as the
latissimus dorsi. Similar to the latissimus dorsi, the teres major muscle
adducts and medially rotates the humerus.
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