You’re probably looking in the mirror, flexing, and wondering why your shoulders look great from the front but somehow "disappear" when you turn around. It’s a common frustration. Most people spend their lives training what they can see—the chest, the biceps, and those front-facing shoulder caps. But the muscles in back of shoulder are actually the secret sauce for that 3D look everyone wants. More importantly, they’re the literal backbone of your joint health. If these muscles are weak, your posture slumps, your bench press stalls, and eventually, things start to click and pop in ways that feel... well, expensive.
Honestly? Most guys and girls in the gym are totally neglecting the posterior chain of the upper body.
We’re talking about a complex network. It isn't just one muscle back there. It’s a literal suspension system. You have the posterior deltoid, the infraspinatus, the teres minor, and the often-overlooked teres major. Then you’ve got the traps and rhomboids acting as the foundation. If these aren't firing, your humerus—that big arm bone—starts migrating forward. That’s how impingement starts. That’s how you end up in physical therapy wondering where it all went wrong.
What Are the Muscles in Back of Shoulder Anyway?
Let’s get technical for a second, but keep it real. When we talk about the muscles in back of shoulder, the star of the show is the posterior deltoid. This is the "rear delt." It’s a small, stubborn muscle that originates on the spine of your scapula and attaches to the side of your arm. Its job is simple: it pulls your arm backward. Think of a rowing motion or a reverse fly.
But it’s not alone.
Deep underneath the deltoid, you have the rotator cuff members. The infraspinatus and teres minor are basically the "bouncers" of the shoulder joint. They keep the head of the humerus tucked neatly into the socket. Without them, your shoulder is basically a golf ball sitting on a tee that’s being shaken by an earthquake. Dr. Kelly Starrett, author of Becoming a Supple Leopard, often talks about "stable shoulder positions," and you simply cannot achieve stability if these posterior muscles are offline.
Then there’s the teres major. It’s often called "lat's little helper." It sits just above your latissimus dorsi and helps with internal rotation and extension. While it’s technically on the back, it’s a massive player in how your shoulder looks and functions from the rear.
The Problem with "Invisible" Muscles
Humans have a massive bias toward what we see in the mirror. It's called "mirror muscle syndrome." We over-train the pectorals and the anterior deltoids. This creates a massive strength imbalance. Your front side becomes tight and short, pulling your shoulders forward into that "gamer hunch" or "gorilla posture."
The muscles in back of shoulder become overstretched and weak.
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Imagine a tent. If the front ropes are pulled tight and the back ropes are loose, the pole—your spine—is going to lean. Eventually, it collapses. In your body, that collapse looks like chronic neck pain, tension headaches, and rotator cuff tears. According to the Journal of Orthopaedic & Sports Physical Therapy, shoulder impingement syndrome is frequently linked to a lack of posterior shoulder strength and scapular dyskinesis. Basically, your shoulder blade isn't moving right because the muscles behind it are asleep at the wheel.
How to Actually Feel Your Rear Delts Working
Here is the thing. Most people suck at training their rear delts. They go to the "Reverse Pec Deck" machine, load up way too much weight, and start swinging their arms.
Stop doing that.
The muscles in back of shoulder are relatively small. If you use too much weight, your massive back muscles—the lats and traps—will just take over the movement. You’ll feel a pump in your middle back, but your shoulders will stay flat. To fix this, you need to lighten the load and focus on the "mind-muscle connection." It sounds like "bro-science," but it’s actually about motor unit recruitment.
Try this: hold your arm out in front of you. Turn your thumb down toward the floor. Now, move your arm back at a 45-degree angle. You should feel a specific "pinch" right on the back corner of your shoulder. That’s it. That’s the spot.
The Exercises That Actually Work
Forget the standard heavy rows for a minute. If you want to target the muscles in back of shoulder, you need precision.
- Face Pulls: These are the gold standard. Use a rope attachment on a cable machine. Pull toward your forehead, but—and this is the key—pull the ends of the rope apart as you get closer to your face. You want to end in a "double bicep" pose. This hits the rear delts and the external rotators (infraspinatus/teres minor) simultaneously.
- Band Pull-Aparts: Do these every single day. Seriously. Take a light resistance band, hold it in front of you, and pull it across your chest. Keep your arms straight. Do 100 reps throughout the day. It’s about volume and reminding your brain that these muscles exist.
- Rear Delt Swings: Credit to the late John Meadows for this one. You lie face down on an incline bench with dumbbells. Instead of a full range of motion, you just "swing" the weights in the bottom half of the movement with high reps (20-30). The pump is agonizing, but it works.
The Connection Between the Scapula and the Shoulder
You can't talk about muscles in back of shoulder without talking about the shoulder blade (scapula). Your shoulder doesn't just sit on your ribcage; it floats on a bed of muscle. If your serratus anterior or your lower traps are weak, your shoulder blade won't "set" properly.
This creates a "winging" effect.
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When the scapula isn't stable, the posterior deltoid can't produce maximum force. It’s like trying to fire a cannon from a canoe. You need a stable platform. This is why many physical therapists, like those at Mayo Clinic, recommend "scapular squeezing" exercises before you even start lifting heavy weights. You have to "prime" the system.
Why Your Posture Is Ruining Your Gains
Let's be honest. You're probably reading this while hunching over a phone or a laptop. Your chin is tucked, and your shoulders are rolled forward. In this position, the muscles in back of shoulder are in a state of "autogenic inhibition." They are literally being told by your nervous system to stay relaxed because they are being stretched so far.
If you spend 8 hours a day in a hunch, a 45-minute gym session isn't going to fix it unless you are intentional.
Focus on "chest up" cues. Not just in the gym, but everywhere. When these muscles are strong, they naturally pull your shoulders back into a proud, healthy position. You’ll actually look taller. You’ll breathe better. You might even stop getting those weird "knots" under your shoulder blades that your partner is tired of massaging.
Common Misconceptions and Myths
A lot of people think that "Back Day" is enough to grow the muscles in back of shoulder.
It’s not.
While heavy rows and pull-ups do involve the posterior deltoid, they aren't the primary movers. Your lats are much bigger and more efficient at those movements. If you want the "boulder shoulder" look, you have to treat the rear deltoid as a primary muscle group, not an afterthought.
Another myth? That you need to train them with heavy triples or fives.
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The posterior shoulder is largely composed of slow-twitch muscle fibers. These respond much better to time under tension and higher repetition ranges. We are talking 15, 20, or even 50 reps. You want to flush the area with blood. Heavy weights usually lead to "shrugging," which means your upper traps are doing the work, not your shoulders.
Nuance: The Role of the Rotator Cuff
It is worth noting that while we want these muscles to look good, their primary role is protection. The infraspinatus is one of the most commonly injured muscles in the human body. Why? Because it’s tiny and we ask it to do too much. When you throw a ball or bench press, that muscle is working overtime to stop your arm from flying out of the socket.
If you only train for aesthetics and ignore internal/external rotation exercises, you’re building a fast car with no brakes. Eventually, you’re going to hit a wall.
Practical Steps for Immediate Improvement
If you want to fix your rear shoulders, you need a plan that goes beyond "I'll do some face pulls at the end."
Start your workout with the back. Instead of starting with heavy presses, start with two sets of band pull-aparts or face pulls. This "wakes up" the posterior chain and actually makes your heavy presses feel more stable. It’s called "successive induction."
Change your grip. On your rows, try using a wide, overhand grip and pulling the bar or handle toward your upper chest/ribcage rather than your belly button. This flares the elbows and forces the muscles in back of shoulder to take the brunt of the load.
Look at your volume. Are you doing 12 sets of chest and only 3 sets of rear delts? Fix the ratio. For every "push" set you do, you should be doing at least one—if not two—"pull" sets. This 2:1 ratio is a staple in the programs of world-class strength coaches like Joe DeFranco.
Control the negative. When doing rear delt flies, don't just let the weights drop. Squeeze at the top for a full second, then take three seconds to lower the weight. The eccentric (lowering) phase is where most of the muscle damage—and subsequent growth—happens.
Assess your mobility. If you can't reach behind your back or touch your hands together in a "scratch your back" test, your internal rotators (the front) are too tight. Stretch your pecs so the muscles in the back actually have the room to contract fully.
Stop thinking of your shoulders as just those caps on the side. Think of them as a 360-degree structure. When you prioritize the back, the front looks better, the joints feel better, and you stop looking like a caveman. It’s not about lifting the heaviest weight in the room; it’s about lifting the right way for the right muscle. Consistent, high-volume, targeted work is the only way to wake up those sleeping giants on your back.