Rear and Posterior Delts (Naming Is the Only Difference)

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A man with flexing his rear, or posterior deltoids from each side of his body.

I used to wonder what the differences in location and function of the “rear” and “posterior” delts were. After researching, I learned that this muscle’s anatomical and general name is expressed interchangeably.

Naming is the only difference between the rear delt and the posterior delt. It is one muscle located on the back of the shoulder. Rear is the common name variation, while posterior is the anatomical term. Both indicate that the muscle is toward the back.

Below I’ll explain what rear and posterior mean exactly and why this portion of the delt has these two names. I’ll also explain the functions and provide some exercises you can do to grow this muscle.

The Difference Between the Rear and Posterior Delt

The posterior delt is often referred to as the rear delt since this is a more descriptive term to help the everyday gym bro decipher its location. In relation to the front and side delt, the rear delt is posterior, since it’s on the back.

Furthermore, posterior is the anatomical wording to label muscles that are on the back side of the body, or closer to the back of the body relative to another muscle. That is why the rear delt is also called the posterior delt.

For example, the front delt is on the front of the body and is also called the anterior delt since anterior means towards the front of the body. The side delt is referred to as the lateral delt since lateral refers to the outside of the body.

This explains why the rear delt is called the posterior delt because again, it is located on the back of the body, posterior to the other two delt heads.

It is also part of the posterior chain, which is a broad categorization for all of the muscles on the back of the body. This includes the traps, lats, hamstrings, calves, and of course the rear delts.

Posterior DeltoidRear Deltoid
The posterior deltoid is the anatomical name to describe this section of muscle fibers which are located toward the back of the body, posterior to the anterior and lateral deltoids.The rear deltoid is the general name to describe this section of muscle fibers as being located on the rear of the three-headed shoulder muscle.

It’s important to note that the delt is one shoulder muscle with three heads: the rear, side, and front. With this in mind, the term rear delt helps distinguish its location on the shoulder from the other two heads.

Calling them the posterior delt specifies that they’re located on the back of the body, while the term rear delt identifies them as being on the back of the shoulder. There are no other differences besides this interchangeable wording.

The Posterior and Rear Delts Are the Same Muscle

Since the posterior and rear delts refer to the same section of muscle fibers, these terms are used interchangeably in many videos and articles. This can be confusing, so here’s a way to help you remember.

The posterior delts are the same muscle as the rear delts and are located on the rear side of the shoulders, posterior to the front and side delts. This location on the shoulder in correlation to the other delt heads is why it has two interchangeable names.

By remembering that, you’ll be able to overcome any confusion when trying to learn new exercises for the rear head of the delt. You also need to know the functions of this posterior muscle to properly train it, which I’ll cover below.

Importance of the Posterior, or Rear Deltoids

Many people try building their posterior deltoid muscles without knowing exactly what they are. To properly strengthen them, you should know how they correlate to and control the shoulders.

The posterior, or rear deltoids are the muscle fibers found above the back of the upper arm on the shoulder. They merge with the front and side deltoids at the middle of the upper arm bone.

Here’s a closer look at their insertions on the shoulder and arm, and how they control certain joint movements.

  • The rear/posterior delts originate on the spine of the scapula, left of the side delts.
    • Feel from the front of your collarbone to the back of your shoulder blade. The bone in the back is the spine of the scapula and is above the rear delt.
  • The muscle fibers move downward toward the outer middle of your upper arm where they merge with the side and front delts.
  • Controls the shoulder joint when moving the arm behind the body via horizontal abduction and shoulder extension, or when rotating the forearm outwards through external rotation.
  • Supports the rotator cuff muscles during external rotation.
  • Important for developing a balanced physique.
  • Promotes pulling power and keeps the shoulder joints stable in deadlifts and rowing exercises.
    • You’ll have better scapular control, enabling you to move your shoulder blades through retraction and protraction.
  • Prevents the front delts from pulling your shoulder joints forward and out of alignment. This would otherwise cause an excessive and painful amount of internal rotation.

Effective Exercises for the Rear/Posterior Delts

So, you know the importance of the rear/posterior delts and how they contribute to the movement of the shoulders. Now’s the time to exercise this small section of muscle fibers.

Since they’re often hard to stimulate, isolation movements are my favorites:

  • Reverse fly:
    • The movement pattern is the opposite of the standard fly, so instead of training the chest and anterior delts, you’ll train the upper back and posterior delts.
    • These can be performed with dumbbells, cables, or a pec deck machine.
  • Band pull-aparts:
    • This exercise elicits an intense mind-to-muscle connection in the rear delts.
  • External rotations:
    • The rear delts provide support to the rotator cuff muscles during this movement.
  • Face pull:
    • Face pulls technically aren’t an isolation movement as the upper back and side delts are heavily recruited as well.
    • Nonetheless, the shoulder movement involves horizontal abduction, which is a main function of the posterior delts.

If you don’t have the equipment to perform these exercises, it’s all good. Check out my article with a few modified versions to work your rear, or posterior delts at home.

Eric De Cremer
Eric De Cremer

Eric is an NCCA-accredited Certified Personal Trainer and competitively trained powerlifter. Feel free to contact him anytime at!