Focus Physique
Combat Underdeveloped Rear Delts – Training the Posterior Deltoid!

The common piece of knowledge given when it comes to building the shoulders is to hit them from all different angles. Even with this bit of information though, we often forget the importance of training the rear delt directly and consistently! This leads to the classically underdeveloped rear delts.

Many lifters have trouble bringing up the posterior deltoid and the reason is that many didn’t work them enough from the start. Now we’re playing a game of catchup!

This article will give you the anatomy of the rear delt, tell you how to activate them optimally in rear delt exercises such as the rear delt fly, and how to train for maximum growth so you can reach your ideal aesthetic!


Anatomy of the Posterior Deltoid

This is the anatomy of the anterior deltoid which is actually made up of three parts.

The posterior deltoid is commonly known to be one of the three heads of the shoulder muscle. Fundamentally this is true, but when broken down further, the posterior deltoid can be broken down to three distinct parts.

These three parts are the segments of the posterior deltoid broken down by intramuscular tendons. This means the posterior can and does pull from slightly angles and in totality these intramuscular tendons make up the posterior deltoid.

This is an interesting note because training with a different grip or at a different angle may aid in better total development!

When we look at the muscle fiber distribution of the rear deltoid, it has about 50% Type I muscle fibers 50% Type II muscle fibers.

The primary function of the posterior deltoid is horizontal abduction. This is essentially having the arms straight out and then pulling them back.


The Rear Delts Influence on Your Aesthetic

Along your journey, you may have seen the impact of fully developed rear delts on one’s aesthetic.

When the rear delt is developed in proportion with the chest and built front delts, it has a profound impact on one’s physique! It aids in good posture which will create a more powerful and wide looking chest. From a side angle, the shoulder looks capped and massive!

When one’s physique has underdeveloped rear delts, this can contribute to the appearance of rounded shoulders and this slouched posture doesn’t project a powerful physique. From a side view we again will see the appearance of rounded shoulders with a lack of that coveted “capped” shoulder appearance.


Why Underdeveloped Rear Delts are Common

The posterior deltoid could nearly be considered a forgotten muscle. Along with this, there are a few reasons why they aren’t up to par with the development of the surrounding muscles!

As mentioned earlier, the importance of directly working this muscle isn’t usually realized until you begin to physically notice it.

It’s also not enough to just do back exercises without direct work of the rear delts.

When we look at the muscle activation of the rear delts during an exercise such as the cable row in comparison with an isolation exercise such as a rear delt fly, it’s essentially the same. Unfortunately, direct work is still needed to bring up underdeveloped rear delts!

Another factor is that many have a hard time activating the rear delts because of a lack of knowledge how to and the anatomy of the posterior deltoid. This will be explained later!


Training Considerations

Before we jump into training and exercises to combat underdeveloped rear delts, we need to consider a few things first!

Earlier I mentioned that the posterior deltoid muscle is about 50/50 when it comes to muscle fiber distribution. Typically, this would mean that training in most rep ranges, even heavier rep ranges such as 6 may be a good approach for maximum muscle growth.

The rear delt is different though. Going too heavy with rear delt exercises often leads to a lack of optimal muscle contraction of the posterior deltoid, especially if you have never felt your rear delts work in the first place. In addition to this, it also causes other, bigger muscles, to come into play such as the upper traps.

You see this especially in rear delt flys! So, generally a rep range of 8 – 15 will be best for most direct rear delt exercises!

The next thing you’ll want to consider is the best way to activate the rear delt!

When we look at EMG testing, which is essentially measuring muscle activation, we see that the rear delt is most responsive with shoulder abduction slightly below horizontal.

Let me decipher that! This is basically saying you will get the best rear delt activation when the arms are pulling back and pointed down slightly.

This is good to keep in mind when choosing compound back exercises and when doing direct rear delt exercises.

Now that we understand how to train the muscle itself, it’s time to program rear delt training into your routine. The best day to work rear delts is when you are doing back.

The reason being is that you are already working rear delts on back day so the added direct rear delt work will be plenty of stimulus for them to grow!


Rear Delt Exercises for Maximum Growth!

Two of these exercises are direct rear delt exercises and one is a compound back exercises that stimulates the rear delt effectively. Remember though, if you are trying to combat underdeveloped rear delts, then you need to do direct rear delt work!


Cable Rows

The cable row is a great compound back exercise to help bring up underdeveloped rear delts
The cable row

Exercise Type: Compound (multi-joint)

The cable row is a great option for back in a rear delt specialization training routine! When we look at the motion of it, we are keeping the arms below horizontal and bringing them back. This is generally that optimal zone for maximum rear delt activation!

In addition, most can do a decent amount of weight on cable rows!

That makes this a great compound movement and one I would recommend implementing into a rear delt specialization routine.


Proper Form

Once you have grabbed the handle, you will want to sit upright in good posture with the chest up, back slightly arched, and shoulders slightly retracted.

You’ll want to pull the handles to you in a range between the belly button and sternum with the elbows beside the body.

Upon returning to the starting position, make sure to not over extend in the shoulder and round the back. This will ensure safety and that all the right muscles are working the whole time.


The Rear Delt Fly

The rear delt fly is a great exercise when done with proper form and makes for a great rear delt exercise
The rear delt fly. I’d also reccomend getting lower than pictured above as described under the proper form section!

Exercise Type: Isolation

Although certain compound movements are great, often trainees end up with underdeveloped rear delts because they haven’t done direct rear delt work! This is when a classic exercise such as the rear delt fly comes in handy.

I would recommend doing these isolation exercises after the big compound movements in your routine. The exception to this would be certain advanced bodybuilding techniques.


Proper Form

The first step is to pick the proper weight. This is very important because if you go to heavy, larger muscles such as the traps will do most of the work. I don’t recommend going below 8 reps on rear delt flys.

From here you will want to hip hinge by sending the hips back, keeping the lower back flat and strong, and finding a bend in the knees. Let the arms hang naturally and don’t retract the shoulder blades. You will want your body to be parallel or nearly parallel with the floor.

Now we have our weight and are in the starting position.

When executing proper form on the rear delt fly, imagine yourself extending the arms down and outward. The reason being is that the posterior deltoid is attached to the scapulae, not the middle of the back.

This motion eliminates excessive retraction of the shoulder blades to ensure that the rear delts are doing the work.


Rear Delt Reverse Barbell Raise

The rear delt reverse barbell raise is the best rear delt exercise to combat underdeveloped rear delts.
The starting position.
The rear delt reverse barbell raise is the best posterior deltoid exercise
The end of the repetition.

Exercise Type: Isolation

The rear delt reverse barbell raise is definitely in the forgotten exercise category but works incredibly well like most forgotten exercises!

Again, it would be recommended to do this after your compound movements.


Proper Form

First grab a barbell, if you find the 45 pound one to be too heavy, then drop down to a 35 pound barbell.

From here, while holding the barbell behind your back with palms facing behind you, send the hips back while keeping the chest up and lower back strong and flat. You will also want to have a slight bend in the knees.

In this position, the barbell will be right behind the calves.

Next, you will do the exercise by raising up the barbell as high as possible, holding for a pause in the top, and then coming back down controlled.


Underdeveloped Rear Delts Eliminated!

The main points to be taken away are that lifters often have underdeveloped rear delts because they don’t actually target them.

From here, we need to get adequate activation of the rear delts with proper exercise form and knowledge of what it takes to activate the rear delt.

With consistency and structured training underdeveloped rear delts can be eliminated!


  • Anat, J. (2010, Nov. 30). Anatomical and Functional Segments of the Deltoid Muscle [web log post]. Retrieved April 4, 2018, from
  • Bentley, A. Deltoids [Web log post]. Retrieved April 4, 2018, from

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