Rear Delts Zone Guide
Rear delts, and what your back looks like from behind
The posterior deltoid is a shoulder muscle from every angle except the one your back is actually judged from.
The short answer
Rear delts are the posterior deltoid, and BackMaxx scores them as one of six back zones rather than a shoulder accessory, because from behind they are the outer corner of your back. Eight of the 77 corpus movements lead with the Rear Delts zone, the lowest rep target in that list is 12, and not one of them is a barbell movement.
Are rear delts back or shoulders? BackMaxx scores them as back
Rear delts are back. The posterior deltoid crosses the shoulder joint and moves the arm, so an anatomy chart files it under shoulders — but BackMaxx scores a photograph taken from behind, and in that photograph the rear delt is the outer corner of the frame. It gets a number of its own, next to Lat Width, Upper Back, Traps, Lower Back and Symmetry.
The app states the case for the zone in one line: “Rounded shoulders from behind — the detail that pops.”
Rear Delts is also the only zone whose name is a muscle name. The other five are containers holding one to three muscles each.
| Zone | Muscles scored inside it |
|---|---|
| Lat Width | Lats, Teres Major |
| Upper Back | Rhomboids, Lower Traps, Infraspinatus |
| Traps | Upper Traps |
| Rear Delts | Rear Delts |
| Lower Back | Erectors |
One zone, one muscle, nothing to average against. A Lat Width score blends the lats with the teres major, and an Upper Back score blends three muscles, so a heavy rhomboid can quietly carry a lower trap that does nothing. The Rear Delts score has no partner to lean on. It reads the posterior deltoid or it reads nothing, which makes it the least forgiving entry on the muscle map.
The practical consequence is running order. Filed under shoulders, rear delts are the third movement on a push day — after the pressing, after the side raises, at the point in a session where the plan says “if there is time.” Filed under back, they are a zone with a score that either moves or sits there. A stalled number is harder to ignore than an exercise you keep meaning to get to.
What a rounded rear delt actually looks like from behind
Four edges draw a back from behind: the trap slope running out from the neck, a corner at each shoulder, the lat flare underneath, and the waist. Rear delts own the corners.
Without them there is no corner. The line runs down the trap slope, reaches the shoulder, and continues straight into the back of the arm with nothing to break it, so the upper back reads as one wide flat plate with arms bolted to the sides. What people are describing when they call a back finished is the break: a round mass sitting behind and outside the shoulder joint, with a groove between it and the upper trap on the inside, and the armpit line cutting it off from the lat below.
That makes the rear delt a silhouette muscle rather than a surface one. Rhomboid thickness adds detail inside the outline. Rear delt development moves the outline itself, pushing the widest point of your upper body out past the shoulder joint instead of stopping at it.
It is also the detail that survives clothing and camera angle. From directly behind it reads as the two corners. From a three-quarter turn it reads as the mass standing behind the shoulder, separating the arm from the back. Under a t-shirt it is the part of the seam that sits proud.
The Back Score bands put names on where this shows up. Elite, 62 to 69, is “Separation people notice.” Master, 70 to 77, is “Detail under the skin, from every angle.” Rear delts are an every-angle detail, which is why a back can be genuinely wide and still score in the Pro band, 54 to 61 — “Width, and the start of the V” — with the corners left unbuilt.
Rear delts vs upper traps: which one is making your back read narrow
Both sit at the top of the back and both change the top line, in opposite directions. Upper traps build up and in, filling the slope between neck and shoulder. Rear delts build out, extending the line past the shoulder. Grow only the first and the top of your back climbs toward your neck; the shoulders end up looking like the bottom of a ramp rather than the ends of a bar.
| Upper Traps | Rear Delts | |
|---|---|---|
| Zone it is scored inside | Traps | Rear Delts |
| Anatomical name | Trapezius (upper) | Posterior deltoid |
| Movements tagging it, of 77 | 12 | 16 |
| Movements it leads | 6 | 8 |
| Direction it builds the outline | Up and inward, toward the neck | Out and backward, past the shoulder |
| Lowest rep target in its list | 10 | 12 |
| Barbell movements leading its zone | 2 | 0 |
| How the app says to load it | “Heavy, simple loading — shrugs and carries” | “Light weight, strict form, more sets than you think” |
Exactly two movements in the corpus tag both muscles: the Upright Row and its dumbbell version, both intermediate, both 3 x 10–12. Everything else picks a side. That is the honest answer to why a back that shrugs heavily every week can still read narrow from behind — twelve movements are feeding the slope and none of them is feeding the corners.
The reverse case exists too. Corners without a slope gives you a top line that runs flat and wide but drops away sharply either side of the neck. Width from behind is the distance between the two corners; shape is what happens between them. The Traps & Rear Delts block trains both because neither one alone finishes the top of a back.
Rear delt exercises for back, sorted by what you have to train with
Eight of the 77 movements lead with the Rear Delts zone, and the posterior deltoid is the first-listed muscle in all eight. Six of them work at home — the highest home-capable share of any zone in the corpus. Not one of them is a barbell movement.
| Equipment | Movement | Sets x reps | Home | What only this one does |
|---|---|---|---|---|
| Resistance Band | Band Pull-Apart | 3 x 15–20 | Yes | The only movement in the eight tagged with Rhomboids — it opens the arms and retracts the blades in the same rep |
| Resistance Band | Banded Rear Delt Fly | 3 x 15–20 | Yes | Tension climbs as the arms open, so the hardest point is the top, where a dumbbell version is at its easiest |
| Dumbbell | Rear Delt Fly | 3 x 12–15 | Yes | Hinged, elbows soft, arms raised wide — the version where “light weight, no swinging” is written into the cue |
| Dumbbell | Bent-Over Rear Delt Raise | 3 x 12–15 | Yes | Torso held near parallel to the floor and the lift led with the pinkies, the only cue in the zone that specifies hand rotation |
| Machine | Reverse Pec Deck | 3 x 12–15 | No | Chest on the pad removes the hinge, so there is no torso movement left to cheat the last reps with |
| Cable | Cable Rear Delt Fly | 3 x 12–15 | No | The zone’s only intermediate movement: cables crossed, standing tall, resistance that never goes slack at the top |
| Bodyweight | Arm Circles | 2 x 30–40s | Yes | Timed rather than counted, small circles growing to big ones in both directions |
| Bodyweight | Cross-Body Shoulder Stretch | 2 x 20–30s | Yes | The zone’s only stretch, and the only entry that is not a working set |
The eight movements that pick rear delts up second
Another eight movements carry the posterior deltoid without leading with it. Where they sit in each movement’s muscle list tells you how much to expect from them.
| Movement | Equipment | Zone it leads | Sets x reps | Where rear delts rank in its muscles |
|---|---|---|---|---|
| Face Pull | Cable | Traps | 3 x 12–15 | 2nd, behind Infraspinatus |
| Banded Face Pull | Resistance Band | Traps | 3 x 15–20 | 2nd, behind Infraspinatus |
| Upright Row | Barbell | Traps | 3 x 10–12 | 2nd, behind Upper Traps |
| Dumbbell Upright Row | Dumbbell | Traps | 3 x 10–12 | 2nd, behind Upper Traps |
| Chest Supported Row | Machine | Upper Back | 3 x 8–12 | 3rd, behind Rhomboids and Lower Traps |
| Prone T Raise | Bodyweight | Upper Back | 3 x 10–15 | 3rd, behind Rhomboids and Lower Traps |
| Prone Y Raise | Bodyweight | Upper Back | 3 x 10–15 | 3rd, behind Lower Traps and Upper Traps |
| Reverse Snow Angel | Bodyweight | Upper Back | 3 x 8–12 | 3rd, behind Lower Traps and Rhomboids |
Two things jump out of that list. The Face Pull and its banded version are filed under Traps but carry no Upper Traps tag at all, so the movement most people call a trap exercise is doing rear delt and infraspinatus work. And every one of the sixteen movements that touch the posterior deltoid is a horizontal or overhead-plane pull. No pull-up, chin-up, lat pulldown or deadlift in the corpus tags rear delts. Vertical pulling builds the V and contributes nothing to the corners.
How much rear delt volume is enough
More than you are doing, at a load lighter than you want to use. The app’s training note for the muscle is four short clauses: “Small muscle, high frequency. Light weight, strict form, more sets than you think.”
The corpus backs that up with its own defaults. Every working movement in the zone is prescribed at 3 sets. The rep targets are 12–15 for the weighted versions and 15–20 for the banded ones, which means the lowest rep target anywhere in the Rear Delts list is 12. No other zone has a floor above 10.
| Zone | Movements leading it | Lowest rep target | Barbell movements | Advanced movements |
|---|---|---|---|---|
| Rear Delts | 8 | 12 | 0 | 0 |
| Traps | 8 | 10 | 2 | 0 |
| Upper Back | 19 | 5 | 3 | 2 |
| Lat Width | 21 | 4 | 0 | 5 |
| Lower Back | 21 | 4 | 7 | 3 |
Timed holds are excluded from the rep column. Read the table across and the zone’s whole character is in it: no barbell, no advanced variation, no set that ends before rep twelve. There is no heavy version of this work to graduate to, which is the part most lifters get wrong — they wait to feel strong on rear delt flys, and strong is not one of the available outcomes.
Two movements per session at 3 sets each is 6 working sets. Run that twice a week and you are at 12, which is what “more sets than you think” looks like once it is arithmetic instead of advice. Frequency is cheap here because nothing in the list is systemically taxing: a band and a pair of light dumbbells cover four of the eight movements, and neither one leaves you needing a day to recover from it.
The three-week Traps & Rear Delts block
BackMaxx builds programs from your weakest zones, and the one that exists for this problem runs three weeks. Its description in the app: “Three weeks on the two zones most people never train directly: shrugs, face pulls and reverse flys lead, with heavy pulls kept in as the base.” Its tagline is the same three words as the zone payoff — the detail that pops.
| Traps & Rear Delts | |
|---|---|
| Length | 3 weeks |
| Sessions per week | 3 |
| Zone leading each session | Traps, then Rear Delts, then Upper Back |
| Pull-up bar needed | No |
| Movement pool it draws from | 8 Traps-lead, 8 Rear Delts-lead, 19 Upper Back-lead |
Three weeks rather than four is a consequence of the movement pool. The four-week blocks lead with Lat Width and Upper Back, zones holding 21 and 19 movements with five and two advanced variations to climb into. Traps and Rear Delts hold eight each, and between them they contain zero advanced movements. There is no fourth-week escalation available, so the block ends while the work is still sharp.
The third session leading with Upper Back is not filler. Five of the sixteen rear-delt movements are Upper Back-lead exercises picking the posterior deltoid up third, so that session keeps feeding the zone even when it is not the headline. The full block sequence shows the rotation session by session.
Rear Delts also leads a session in the Thickness Block and in Posture Reset — three of the five Focus Programs, more than Traps, Lat Width or Lower Back appear in. For a zone with eight movements and no barbell, it turns up in the plan a lot.
How to tell whether Rear Delts is your lowest zone
Scan, then read the corners. A Back Score is one number, but the six zone scores under it are what tell you where to spend the next three weeks, and the pattern that sends people to this page is a specific one: Lat Width and Upper Back sitting comfortably, Rear Delts trailing both by a visible margin. That is a back built by rows and pull-ups, which is most backs, since no vertical pull in the corpus touches the posterior deltoid.
If Rear Delts is not your low score, the fix is somewhere else and the block above is the wrong one to run — the six-zone breakdown covers what each score is actually reading. If it is, the eight Rear Delts movements are the pool to build from, and six of them need nothing beyond a band and a pair of dumbbells you can already handle for fifteen strict reps.
Key takeaways
- BackMaxx scores Rear Delts as one of six back zones, and it is the only zone whose name is also a muscle name — one zone, one muscle, nothing to average the score against.
- Eight of the 77 corpus movements lead with the Rear Delts zone, and the posterior deltoid is the first-listed muscle in all eight of them.
- No barbell movement leads the Rear Delts zone and no advanced movement exists in it: 7 of the 8 are beginner, and the Cable Rear Delt Fly is the only intermediate one.
- The lowest rep target anywhere in the Rear Delts list is 12, higher than every other zone’s floor — Traps stops at 10, Upper Back at 5, Lat Width and Lower Back at 4.
- No pull-up, chin-up, pulldown or deadlift in the corpus tags the rear delts, so a back built on vertical pulling scores the V-taper and leaves the corners empty.
- Rear Delts leads a session in three of the five Focus Programs, including the three-week Traps & Rear Delts block, which runs short because neither of its two zones has an advanced movement to progress into.
What the research says
Every rear-delt movement in the library is written at 12 reps or more. That is not a compromise for growth, and two lines of research show why.
- Across 28 studies in a network meta-analysis, light loads that allowed more than 15 reps per set grew muscle as well as moderate and heavy loads when sets were taken to failure. [1]
- What light sets need is closeness to failure: in exploratory meta-regressions of the reps-in-reserve literature, muscle growth improved the nearer to failure each set was stopped. [2]
Sources
- Lopez P, Radaelli R, Taaffe DR, et al. (2021). Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis. Med Sci Sports Exerc. PubMed 33433148 · doi:10.1249/MSS.0000000000002585
- Robinson ZP, Pelland JC, Remmert JF, et al. (2024). Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions. Sports Med. PubMed 38970765 · doi:10.1007/s40279-024-02069-2
Frequently asked questions
Are rear delts back or shoulders?
Anatomically the rear delt is the posterior deltoid, part of the shoulder. Visually, from behind, it is back — which is why BackMaxx gives it one of six zone scores rather than filing it with pressing. The zone’s payoff line is “Rounded shoulders from behind — the detail that pops.” Scored as back, it competes for volume with rows instead of with side raises.
What weight should I start with for rear delt exercises?
Light enough to hit the bottom of the rep range with no torso movement. Every weighted movement in the Rear Delts zone is prescribed at 3 sets of 12–15, and the banded ones at 15–20, so the load is whatever lets you finish twelve strict reps and still pause at the top. The app’s note for the muscle: “Light weight, strict form, more sets than you think.”
How often should I perform rear delt exercises for best results?
More often than anything else on your back. The muscle’s training note reads “Small muscle, high frequency,” and nothing in the eight-movement list is taxing enough to need a recovery day — no barbell, no advanced variation, no set below twelve reps. Two movements at 3 sets each, twice a week, is 12 working sets and a realistic starting point.
How do you make your back look wider from behind?
Width from behind is the distance between the two shoulder corners, and rear delts are what puts the corners out past the shoulder joint. Lats widen the flare below the armpit; upper traps build up and inward toward the neck. Only the posterior deltoid extends the top line outward, which is why a back full of rows can still read narrow across the top.
Can you train rear delts at home without weights?
Six of the eight Rear Delts movements are home-capable, the highest share of any zone. Two need a resistance band — Band Pull-Apart and Banded Rear Delt Fly, both 3 x 15–20 — two need dumbbells, and two need nothing: Arm Circles at 2 x 30–40s and the Cross-Body Shoulder Stretch. Only the Reverse Pec Deck and Cable Rear Delt Fly are gym-only.
Do rows and pull-ups train the rear delts?
Rows partly, pull-ups not at all. Four rowing and prone movements tag the posterior deltoid third in their muscle list, behind the rhomboids and lower traps, so they contribute without leading. No pull-up, chin-up, pulldown or deadlift in the 77-movement corpus tags rear delts at all. Vertical pulling and hinging are the wrong plane for this muscle.
Why is the face pull filed under Traps and not Rear Delts?
Because its primary zone is Traps, though the tags tell a more interesting story: neither the Face Pull nor the Banded Face Pull carries an Upper Traps tag. Both list Infraspinatus first, rear delts second, and lower traps third. The movement most people run as trap work is rear delt and infraspinatus work sitting in the Traps column.
Find out where your back actually stands
One photo, a Back Score out of 100, six zones and eight muscles ranked — then a plan built on whatever came out lowest.
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