You've probably spent hours hammering your lats or obsessing over your bench press form. Most people do. But there's a high chance you're completely ignoring the two little muscles tucked right under your armpit that actually dictate whether your shoulder stays healthy or ends up in a sling. They're called the teres minor and major. While they share a name, they’re basically the "Odd Couple" of the human anatomy. One is a rotator cuff muscle that keeps your arm in its socket; the other is basically a "little lat" that helps you pull things toward you. If they get out of sync, your shoulder starts clicking, your overhead press stalls, and you’re suddenly googling "rotator cuff surgery recovery times" at 2:00 AM.
Let's get real about why these two matter.
The Secret Identity of Teres Minor and Major
The teres minor and major are often lumped together because they sit right next to each other, but their jobs couldn't be more different. Think of the teres minor as the elite security guard for your shoulder joint. It’s one of the four rotator cuff muscles. Its main gig? External rotation. When you rotate your forearm away from your body, that’s the minor doing the heavy lifting. More importantly, it provides posterior stability. Without it, the head of your humerus (your arm bone) would just slide around like a loose marble in a saucer.
Then you have the teres major.
It’s bigger, beefier, and honestly, a bit of a glory hog. It’s not part of the rotator cuff. Instead, it works in tandem with your latissimus dorsi. Because of this, many kinesiologists call it "lat’s little helper." It helps with internal rotation and pulling your arm back and down. If you’re doing a heavy row or a pull-up, the teres major is screaming for attention.
Here is the weird part: despite being neighbors, they often work against each other. The minor wants to rotate your arm out. The major wants to rotate it in. When the major gets too tight—which happens to almost everyone who sits at a desk all day—it overpowers the minor. This tug-of-war is exactly why your shoulders feel "tight" even after you stretch.
Why Your Shoulder Hurts (and why it's probably the Minor)
If you feel a sharp, biting pain in the back of your shoulder when you reach for a seatbelt or try to throw a ball, the teres minor is usually the culprit. It’s a tiny muscle, but it takes a massive amount of abuse.
Specifically, in overhead athletes or lifters, the teres minor can develop trigger points that mimic more serious injuries. I’ve seen people convinced they have a labral tear when, in reality, they just have a nasty knot in their minor. According to research published in the Journal of Shoulder and Elbow Surgery, the teres minor is actually the most common site of "fatty infiltration" in chronic rotator cuff tears, meaning if you don't use it, you literally lose the muscle quality.
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It’s fragile.
The teres major, on the other hand, rarely tears. It just gets stiff. When it gets stiff, it pulls your shoulder forward into that "caveman" posture. You know the one. Rounded shoulders, head poking forward, looking like you’re permanently hunched over a laptop. Because the major attaches to the front of the humerus, it’s a powerful internal rotator. If it's constantly "on," your teres minor has to work double-time just to keep your shoulder from popping out of place. It’s an exhausting, losing battle for the smaller muscle.
Distinguishing the Two in Your Own Body
How do you know which one is bothering you?
Try this: reach your hand behind your back as if you're trying to scratch between your shoulder blades from the bottom. If that hurts or feels restricted, your teres major and lats are likely the tight ones. Now, try the opposite—reach over your shoulder to touch that same spot. If you feel a "pinch" in the back of the armpit, that's often the teres minor struggling to stabilize the joint.
The "Lat's Little Helper" Myth
People talk about the teres major like it’s just a redundant version of the lat. That's a mistake. While they share functions, the teres major is specifically active when the arm is in a specific range of motion—usually when the arm is extended behind the body or when you're starting a pulling movement from a dead stop.
In bodybuilding circles, a well-developed teres major is what gives that "width" right under the armpit. It fills out the "V-taper." But from a functional health perspective, an over-developed teres major without a strong teres minor is a recipe for impingement.
Basically, the major pulls the bone, and the minor stabilizes the pivot point. If the pull is stronger than the stability, you get friction. Friction leads to inflammation. Inflammation leads to bursitis or tendonitis. It’s a domino effect that starts with a simple muscular imbalance.
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Fixing the Imbalance: Real-World Solutions
You can't just "stretch" your way out of a teres minor and major issue. You have to be tactical.
1. Release the Major
Stop trying to stretch your shoulder by pulling your arm across your chest. That usually just irritates the joint capsule. Instead, take a lacrosse ball or a firm foam roller. Place it right on the lateral border of your scapula—the "meaty" part of your back just below the armpit. Lean into it. If you find a spot that makes you want to swear, you’ve found the teres major. Hold it there for 90 seconds. Don’t roll around like a maniac; just breathe and let the muscle melt.
2. Activate the Minor
Once the "bully" (the major) is relaxed, you need to wake up the minor. The best way to do this is through "Face Pulls" or "W-raises."
- Hold a light resistance band.
- Pull it toward your forehead.
- Focus on pulling your thumbs back, not just your elbows.
- You should feel a deep "burn" in the very back of your shoulder.
If you feel it in your traps or your neck, you’re doing it wrong. Lower the weight. This isn't about strength; it's about neurological "waking up."
3. The Eccentric Trick
Muscles like the teres minor respond incredibly well to eccentric loading. That means "the lowering phase." If you’re at the gym, use a cable machine. Set it to waist height. Pull the cable out (external rotation) and then take five full seconds to let it come back in. This slow release forces the teres minor to stay engaged and builds the structural integrity needed to prevent future tears.
The Connection to Posture and Breathing
Here is something most people miss: your breathing affects your teres major.
When you are a "chest breather," your ribcage doesn't expand properly. Your shoulders elevate with every breath. This keeps the teres major and the pectorals in a state of constant low-level tension. Over thousands of breaths a day, this tightens the front of the shoulder and overstretches the back.
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Learning to breathe into your belly and lower ribs actually helps relax the teres major. It’s all connected. You can’t fix a shoulder by looking only at the shoulder. You have to look at the ribcage it sits on. If your ribs are "flared," your scapula (shoulder blade) can't sit flat. If the scapula can't sit flat, the teres minor and major are starting from a disadvantaged position. It’s like trying to win a race while wearing lead boots.
When to See a Pro
Look, I’m all for DIY rehab, but don't be a hero. If you have any of the following, go see a physical therapist or an orthopedist:
- You can’t lift your arm past shoulder height.
- You have "night pain" that keeps you awake.
- Your arm feels weak, like you can’t hold a cup of coffee.
- You heard a "pop" followed by immediate bruising.
These are signs of a full-thickness tear or a neurological issue like Quadrilateral Space Syndrome—where the axillary nerve gets compressed right between the teres minor and major. It’s rare, but it happens, and no amount of foam rolling will fix it.
Actionable Steps for Better Shoulders
To keep your teres minor and major healthy, stop treating your back workouts like a contest of who can move the most weight with the worst form.
First, change your grip. Using a neutral grip (palms facing each other) for rows and pull-ups takes some of the strain off the internal rotators and allows the teres minor to stay in a better position.
Second, prioritize "rear delt" work. Even though the teres minor isn't the rear delt, they work together. Exercises like "Band Pull-Aparts" are boring, but they are the insurance policy your shoulders need.
Third, check your desk setup. If your keyboard is too high, your shoulders are shrugged, and your teres major is shortening. Lower your desk or raise your chair.
The goal isn't just to have big muscles. The goal is to have a shoulder joint that actually works when you’re 60. By balancing the tension between the teres minor and major, you’re not just building a better physique; you’re building a functional body that won't fail you when you need it most.
Start by spending five minutes a day on the lacrosse ball and ten minutes on external rotation. It’s a small investment for a massive payoff in mobility and pain-free movement. Your future self will thank you for not ignoring these two "invisible" muscles today.