In part 2 of this three part series on "Building The Back," I will discuss the middle back. The muscles of the middle back include the:
Deltoid
Infraspinatus
Teres minor
Teres major
Latissimus dorsi
The Deltoid
While the deltoid is just one muscle, it actually consists of three different sets of fibers. The anteroir (front) fibers, the lateral (middle) fibers and the posterior (rear) fibers. Each set of fibers has a slightly different purpose. Therefore, we have to do several different exercises to strengthen all the fibers in the deltoids. However, for the sake of this article we will only be discussing the posterior fibers of the deltoid, because they are the only fibers that assist in the pulling movements which are essential for training the back.
Posterior fibers
The posterior fibers of the deltoid originate from the inferior edge of the spine of the scapula and insert at the lateral (outside) of the humerous (upper arm). These fibers are mostly responsible for extension of the upper arm, but also horizontal abduction. So the posterior deltoid helps move the upper arm backwards in all pulling type motions.
The posterior fibers of the deltoids are best activated when the arm is in a slightly horizontally abducted (30 degree) position. So with this information we can easily see that any kind of rowing movements with the elbows up from the sides at about 30 degrees will hit the anterior delts.
The Infraspinatus
The infraspinatus is one of the smaller muscles in the middle back. It works in conjunction with a muscle called the teres minor to stabilize the scapula. The infraspinatus is vital to maintaining posterior stability of the glenohumeral or shoulder joint. So the infraspinatus is also know as one of the rotator cuff muscles. It originates at the medial (inner) aspect of the infraspinatus fossa (scapula) just below the spine of the scapula. It inserts posteriorly on the humerous or back of the upper arm. The infraspinatus acts to both horizontally abduct and extend the humerus in all pulling type movements.
To strengthen this muscle we can use any pulling exercises that are done by pulling the arm down from a flexed position. The infraspinatus is used to perform chins or lat pull downs.
The Teres Minor
Just under the infraspinatus the teres minor muscle is located. As mentioned earlier, this small muscle functions very similarily to the infraspinatus. The teres minor originates posteriorly on the upper and middle aspects of the lateral border of the scapula and inserts on the upper part of the humerous. As with the infraspinatus, the major jobs of the teres minor in pulling type movements are to horizontally abduct or extend the humerous. This simply means to move the upper arm away from the chest in a horizontal plane or to move the upper arm backwards from a flexed (upward) or neutral position. Since the teres minor and infraspinatus work together chins and pulldowns are both good exercises to strengthen this muscle.
The Teres Major
The teres major is much smaller muscle located just under the teres major. Unlike the teres minor, this muscle assists the latissimus dorsi in pulling movements. In fact, the teres major is best thought of as the latissimus dorsi’s "little helper." The teres major originates posteriorly on the inferior (lower) of the lateral border of the spacula and inserts at the upper part of the humerous. So judging from its origion and insertion points you can see how this muscle, when contracted, also helps in all pulling type movements. Not only does the teres major help to extend or pull the arm down from a flexed position, it also works to adduct the arm to the side from and abducted position. The teres major is best strengthened by pulling exercises such chins, lat pulldowns, pullovers, and rows.
The Latissimus Dorsi
The largest muscle of the middle back is the latissimus dorsi. This muscle is not only the largest but it is also the most powerful muscle used in pulling type movements. The latissimus dorsi originates at the posterior crest of the ilium, the back of sacrum and spiny processes of the lumbar and lower six thoracic vertebrae, and slips from the lower three ribs. The insertion point of the latissimus dorsi is at the medial side of the upper humerous. In other words, it starts from the middle of the spine, all the way down to the base of the spine and spans much of the middle back where it attaches to the inner side of the upper arm. The latissimus dorsi is strengthened by rows, lat pulldowns, pullovers and chins.
Summary
Now, once again.... let’s put all of this together and make it real simple. Here is the basic idea..... pulldowns, pullovers and chins hit the:
Teres major
Latissimus dorsi
Pulldowns and pullups hit the:
Infraspinatus
Teres minor
Teres major
Latissimus dorsi
Rows hit the:
Posterior deltoid
Infraspinatus
Teres minor
Teres major
Latissimus dorsi
References:
1. Chek, P. (1997). Rows, pulls, chins, & the deadlift. In: Gym
Instructor Series, v3. Chek, P. Prod. La Jolla, CA: Paul Chek Seminars.
2. Thompson, C.E. and Floyd, R.T. (1994). The shoulder joint. In:
Manual of Structural Kinesiology, 12th ed. Smith, J.M. Ed. St. Louis,
MS: Mosby-Year Book.