Back muscles
Infraspinatus: the plate under the shoulder blade
It is the flattest muscle BackMaxx scores, it never gets to be strong, and it is the reason a rear delt looks attached to a back instead of stuck on it.
What is the infraspinatus?
The infraspinatus, labelled anatomically as Infraspinatus & teres minor, is the flat plate of muscle covering the back of the shoulder blade below its bony ridge. It turns the upper arm outward rather than pulling it back, so it grows on external rotation and face-pull patterns at light load. It adds separation between the rear delt and the blade.
| Anatomical name | Infraspinatus & teres minor |
|---|---|
| BackMaxx zone | Upper Back |
| What it changes | The plate under the shoulder blade. Separation, and healthy shoulders. |
| How it responds | Trains as a rotator, not a puller. Face pulls and external rotation, never heavy. |
| Exercises tagged | 8 of 77 |
Where the infraspinatus actually sits
The infraspinatus fills the flat hollow on the back of the shoulder blade, below the bony ridge that runs across the top of it. BackMaxx scores it together with the narrow strip along its lower edge, which is why the app labels the pair anatomically: Infraspinatus & teres minor.
Both start on the blade and finish at the top of the upper arm bone. That geometry sets the terms for training it. It begins on a bone that itself moves, it crosses one joint, and its entire job is turning the upper arm outward in its socket and keeping it turned out while the arm works away from the body.
It is also the only one of the eight BackMaxx muscles whose thickness is fenced in by the bone underneath. The blade is the plate. This muscle is the layer of meat sitting on top of it. Nobody grows it enough to change their outline, and that is not what it is for.
What developing it changes about how a back looks
Everything this muscle pays out is separation. From the front and from the side it contributes nothing.
From behind, a filled-in infraspinatus splits the back of the shoulder blade into two readable shapes instead of one flat sheet: a low oval of muscle sitting on the blade, and the rear delt above and outside it, with a hard seam where the two meet. On a lean back that seam is one of the last details to arrive.
It changes the read of the whole Upper Back too. When the blade is bare, the rear delt looks bolted onto a flat panel. Fill the plate under it and the shoulder looks like it grew out of the back. A photo picks that up long before anyone can name which muscle did it.
How it responds: rotation, not pulling
The training note in BackMaxx is blunt — it trains as a rotator, not a puller. Worth spelling out what that means inside a session.
In any row or pulldown the elbow travels backward and downward, and the lats, rhomboids and mid traps absorb that load because they are far larger and far better placed for it. The infraspinatus gets a supporting role and nothing more, no matter what is on the bar. Adding a fourth set of rows does not reach it.
It only becomes the prime mover when the upper arm is asked to rotate outward: the thumb rolling away from the body while the elbow stays where it is. That happens across a short range on a short lever, which is why load has to stay small. Go heavier and the rotation quietly gets replaced by torso lean and elbow bend, and the set turns into a clumsy row.
Face pulls sit in between. The travel toward the face is a row for the traps and rear delts. The finish — hands ending beside the ears, elbows high — is external rotation under tension, held at the point where the muscle is shortest.
The eight BackMaxx movements that load it
Eight of the 77 movements in the corpus tag the infraspinatus, the fewest of any of the eight muscles. That is not an oversight. It is the honest number of things that ask the arm to turn outward.
| Movement | Equipment | Sets x reps | What it asks of the muscle |
|---|---|---|---|
| Face Pull | Cable | 3 x 12–15 | Pull to the ears, then hold the arms rotated out at the finish |
| Banded Face Pull | Resistance Band | 3 x 15–20 | Same finish, with tension highest exactly where rotation is hardest |
| Rear Delt Fly | Dumbbell | 3 x 12–15 | Keeps the arm turned out while it travels away from the torso |
| Bent-Over Rear Delt Raise | Dumbbell | 3 x 12–15 | Pinky-led lift, which is rotation and abduction in one move |
| Banded Rear Delt Fly | Resistance Band | 3 x 15–20 | Elbow-led opening against tension that builds toward the top |
| Cable Rear Delt Fly | Cable | 3 x 12–15 | Constant tension across the arc, with no rest at the bottom |
| Arm Circles | Bodyweight | 2 x 30–40s | Unloaded rotation through a full circle, both directions |
| Cross-Body Shoulder Stretch | Bodyweight | 2 x 20–30s | Lengthens the back of the shoulder instead of loading it |
Read the equipment column again: two dumbbell, two cable, two band, two bodyweight. No barbell, no machine and no pull-up bar movement in the whole corpus touches this muscle. Six of the eight run at home, and seven of the eight are graded beginner.
The zone it rolls into, and why that zone is Upper Back
BackMaxx scores the infraspinatus into Upper Back, which surprises people who see it sitting right beside the posterior deltoid.
The corpus explains it. All eight movements that tag this muscle carry Upper Back as a zone: six list it behind Rear Delts, the two face pulls list it behind Traps, and not one leaves it out. Upper Back is the zone that always comes along.
It matches the payoff, too. Rear Delts is scored as the rounded cap of the shoulder seen from behind. This muscle is flat, it lives on the blade, and what it adds is thickness and detail between the blades and the arm, which is the Upper Back payoff exactly: thickness and the 3D look from the side. The Upper Back exercise list is the right shelf to shop from.
How to tell from a back photo that it is behind
Stand relaxed with the arms at your sides and this muscle hides. You need the arms slightly out from the body, or a hands-on-hips shot, before the area opens up at all.
Then look at the patch bounded by the ridge of the blade above, the rear delt outside it, and the armpit below. Three possible reads:
- One smooth sheet, a rear delt bulging above it and nothing underneath — behind.
- A shallow bump that appears only when you deliberately turn the arm out — early progress.
- A visible oval with a crease separating it from the rear delt, holding its shape with the arm relaxed — developed.
There is a comparative tell as well. If your Upper Back score sits well below your Lat Width and rows and pulldowns are already a habit, the missing tissue is usually on the blade rather than around it. Shoot in the same light every scan: the seam is a shadow, and flat overhead light erases it.
How much work it wants, and how heavy
Small muscle, short range, and it fatigues in a way that never feels like training. Treated as a detail it responds. Treated like a lat it stops moving.
| Spec | Infraspinatus |
|---|---|
| Direct sets per week | 4–8 |
| Reps per set | 12–20, or 20–40 seconds of timed work |
| Load | Light enough that the arm rotates with zero torso movement |
| Frequency | Two or three short exposures, never one long one |
| Placement | After the heavy pulling, or between sets of it |
| Rest between sets | Short. 45 to 60 seconds is plenty |
Reps stay high because the alternative is cheating. Nothing in the corpus that tags this muscle is prescribed below 12 reps, and both banded movements run to 15–20. The three-week Traps & Rear Delts block is where that work stacks up, and it gets there without a single heavy set.
What people get wrong training it
Turning face pulls into rows. Pull to the chest and the elbows drop, which deletes the rotation and hands the set to the mid traps. The finish is the thing you are buying: hands beside the ears, elbows high.
Adding weight. The first symptom is the torso rocking to start each rep. The second is the elbow drifting away from the ribs on rotation work. Either one means the number on the stack is now training something else.
Only ever using it as a warm-up. Thirty seconds of arm circles before pulling is a warm-up. It is not the same thing as two strict sets of flies that finish with the arms shaking, and only the second one builds tissue.
Bands with slack at the finish. A band that goes loose in the last third gives you nothing at the position where the muscle is shortest. Anchor it far enough away that the end of the rep is the hardest part.
Expecting size. This one pays in seams and shadows. Width comes out of a different budget: the lats and teres major.
Best infraspinatus exercises
All 8 movements in the BackMaxx library that load the infraspinatus, grouped as the library groups them.
Browse the full 77-exercise library →
Frequently asked questions
What does the infraspinatus do?
It turns the upper arm outward in its socket, and holds it turned out while the arm works away from the body. That is the whole job. It crosses one joint, runs from the back of the shoulder blade to the top of the upper arm bone, and never acts as the prime mover in a row or a pulldown.
How do you train the infraspinatus?
With external rotation and face-pull patterns at light load. In BackMaxx that means face pulls finished with the hands beside the ears, rear delt flies held in an outward-turned position, and pinky-led bent-over raises. Eight of the 77 movements tag it, all at 12 reps or more, and none of them heavy.
How often should you train the infraspinatus?
Two or three short exposures a week, four to eight direct sets in total. It recovers quickly because the sets are never heavy, and it responds better to frequent light work than one long session. Slot it after the heavy pulling, or between sets of rows, at 45 to 60 seconds of rest.
Are face pulls enough for the infraspinatus?
Face pulls are the best single choice, but only if you finish them properly. The travel toward the face is a row for the traps and rear delts; the rotation happens in the last few inches, hands beside the ears with the elbows high. Pair them with a fly variation so the muscle gets loaded in more than one arm position.
Can you train the infraspinatus at home?
Yes. Six of the eight movements that tag it run at home, and the equipment list is dumbbells, a resistance band, or nothing at all. No barbell, machine or pull-up bar exercise in the corpus touches this muscle, so a gym adds cable versions and very little else.
Which BackMaxx zone does the infraspinatus score into?
Upper Back. Every one of the eight movements that tags the muscle also carries Upper Back as a zone, six of them behind Rear Delts and two behind Traps. The muscle sits on the blade and adds thickness and detail between the blades and the arm, which is what the Upper Back zone is scored on.
Is your infraspinatus the problem?
BackMaxx scores eight back muscles individually from one photo, so you find out whether the infraspinatus is actually what is holding your back back — or whether it is something else.
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