The six parts of the back to train, and what each one gets you

The back you can actually train breaks into six zones: Lat Width, Upper Back, Traps, Rear Delts, Lower Back and Symmetry. Those six are what BackMaxx scores from one photo, and they are the units a session gets built in. Anatomy hands you eight muscles, which is too granular to program around. A mirror hands you a vague impression of your front. Six zones sit in between: specific enough to name what is behind, broad enough that moving one of them changes how your back reads from across a room.

What follows defines each zone, names the muscles it scores, and gives the exercise count behind it in the 77-movement BackMaxx corpus.

The six back zones at a glance

The right-hand column is not marketing copy bolted on afterwards. It is the payoff line the app uses for each zone, and it exists because a zone is only worth training if you can say what it buys you.

Each zone is scored on its own, from a single photo taken with the selfie camera and a 5-second self-timer. The six scores roll up into one Back Score out of 100 and one of nine ranks, from Newbie under 38 to GOAT at 91 and above. Every one of these numbers is a visual estimate meant to point your training somewhere, not a measurement of anything.

The exercise counts below all come from the same 77-movement corpus, where each movement carries one primary zone and up to two secondary ones. That distinction matters more than it sounds: a zone’s primary count tells you how much work exists that aims at it, and its total count tells you how often it gets hit on the way to something else.

Lat Width: the zone that sets your silhouette

“The V-taper. Width from the armpit down.” Lat Width is the outline zone — the one a stranger reads first, because it is the only zone that changes the shape of your torso rather than the texture of it.

Two muscles score here. The Lats (latissimus dorsi) are the V-taper itself, width from the armpit down to the waist, and they want a full stretch at the top and a long range: vertical pulling first, rows second. Teres Major is the small bulge under the armpit that makes the V look wider than it actually is, and it answers to anything that drives the elbow down and back.

Twenty-one of the 77 exercises name Lat Width as their primary zone — tied with Lower Back for the largest block in the corpus. All 21 tag the lats. Seventeen of them also tag teres major. Counting secondary tags, 36 movements touch the zone.

The equipment split is the tell. Those 21 exercises use a Pull-up Bar (6), Bodyweight (6), Cable (4), Machine (2), Resistance Band (2) and a Towel (1). Not one barbell. Not one dumbbell. Width in this corpus comes from pulling from overhead or sweeping a straight arm down, which is why Straight-Arm Pulldown’s cue is to “sweep the bar down with your lats, not your triceps” rather than to add load.

It is also the hardest block to work through. Five of the 21 are rated advanced — more than any other zone — including the L-Sit Pull-up, Weighted Pull-up and Towel Pull-up, where “your grip gives out before your lats”. Twelve are beginner, and 13 of the 21 run at home. Start at Wide-Grip Lat Pulldown, 3 sets of 10–12, or a Dead Hang at 3 sets of 20–40 seconds, then work up. The long version is in the lat width and V-taper guide, and the full block is at all 21 Lat Width exercises.

Upper Back: thickness, and the widest equipment spread in the corpus

Where Lat Width owns your outline, Upper Back owns your profile. The app’s line for it is “Thickness and the 3D look from the side” — the depth that stops a wide back from reading flat the moment you turn side-on.

It is the only zone that scores three muscles. Rhomboids give thickness between the blades and the ridge down the middle, and they grow from rowing where you actually squeeze the blades together and pause — retraction first, load second. Lower Traps (trapezius, mid and lower) pull the shoulder blades down and back, and are almost never trained directly: Y-raises and prone work at light load do more here than heavy rowing. Infraspinatus (infraspinatus and teres minor) trains as a rotator rather than a puller, which is why it is tagged on only eight movements in the whole corpus — face pulls, rear delt flys, arm circles and a cross-body shoulder stretch — and never on anything heavy.

Nineteen exercises claim Upper Back as their primary zone, but 55 of the 77 touch it — 36 carry it as a secondary. No other zone comes close. Almost everything you do for your back brushes the upper back whether you aimed there or not, which is exactly why an underdeveloped Upper Back score is so common: incidental work keeps it alive without ever making it thicker.

The movements split cleanly into two families. Rows lead — Barbell, Pendlay, T-Bar, Meadows, Chest Supported, Machine, Inverted, Doorway, Towel and single-arm variants on cable, dumbbell and kettlebell. Behind them sit the face-down raises: Prone T Raise, Prone Y Raise, Reverse Snow Angel, Scapular Push-up.

Nine of the corpus’s ten equipment types appear inside those 19 exercises. The only one missing is a pull-up bar. Upper Back is the zone least able to blame your setup: a doorway and a towel each get you a row. If you want the machine version of the cue, take Chest Supported Row at 3 sets of 8–12 and “press your chest into the pad the whole set so only your back does the pulling.” The upper back thickness guide covers the rest.

Traps: the frame, and the one zone with nothing bodyweight

Traps is the zone that reads as strong in a T-shirt, because the slope from neck to shoulder is the one piece of back development visible from the front. The payoff line is “The frame around your neck and shoulders.”

One muscle scores here: Upper Traps (upper trapezius). It responds to heavy, simple loading — shrugs and carries — and to time under tension more than to rep count.

Eight exercises take Traps as their primary zone, and 21 touch it in total. Two patterns cover all eight. Either load hangs in your hands and you lift or carry it (Barbell Shrug, Dumbbell Shrug, Kettlebell Shrug, Farmer Carry), or you pull toward your face or chin (Face Pull, Banded Face Pull, Upright Row, Dumbbell Upright Row).

Which produces the one hard constraint in the map: all eight need an implement. Dumbbell (3), Barbell (2), Cable (1), Resistance Band (1), Kettlebell (1). Of the five zones that have primary exercises at all, Traps is the only one with no bodyweight entry, and only five of the eight are listed as home-viable. The flip side is that none of them are advanced — six beginner, two intermediate — so the ceiling on technique is low even though the floor on equipment is not.

The corpus’s only loaded carry lives here too: Farmer Carry, 3 rounds of 30–45 seconds, “stand tall with your shoulders back, and walk without letting them slump.” And traps get paid indirectly by heavy hinging — of the 12 exercises in the corpus that tag Upper Traps, five sit inside the Lower Back block, on deadlift variants and the Kettlebell Swing.

Rear Delts: the small block a photo gives away first

You only ever see rear delts from behind, which is why they go unnoticed longer than anything else on this map. The zone’s line is “Rounded shoulders from behind — the detail that pops”, and pops is the right verb: it is tied with Traps for the smallest block in the map, and it is one of the first things a photo gives away.

One muscle: Rear Delts (posterior deltoid). Small muscle, high frequency — light weight, strict form, more sets than you think.

Eight exercises lead with it and 16 touch it. Six of those eight also tag Infraspinatus, because the arms-wide-and-back sweep hits both, so the two get scored off the same movements. Nothing in this block is prescribed below 12 reps, and it is the only zone where that holds: Band Pull-Apart and Banded Rear Delt Fly at 3 sets of 15–20, then Bent-Over Rear Delt Raise, Rear Delt Fly, Cable Rear Delt Fly and Reverse Pec Deck at 3 sets of 12–15.

It is also the cheapest zone to bring up. Seven of the eight are beginner, none are advanced, and six run at home: two band movements, two dumbbell flys, and two that need nothing in your hands at all. Band Pull-Apart asks only that you “pull it apart until it touches your chest, blades squeezed” — no bench, no rack, no loading decision.

Lower Back: the Christmas tree

Lower Back carries the only payoff line in the map that is half look and half job description: “The Christmas tree, and the base every heavy pull needs.” The corpus reflects that split exactly.

One muscle scores it: the Erectors (erector spinae), the two columns that run down either side of your midline and make the Christmas tree. They live on hinge patterns and holds, and they recover slowly, so two hard sessions a week is plenty.

Twenty-one exercises name Lower Back as their primary zone, tied with Lat Width for the biggest block, and all 21 tag the erectors. Only three exercises anywhere else carry it as a secondary, for a total of 24 — the narrowest gap between primary and total of any zone. Read that as a warning: nothing else in your session trains this by accident.

The equipment split here is unique. Bodyweight (7) and Barbell (7) tie, which is to say the zone is served equally by nothing at all and by the heaviest object in the building. Dumbbell (3), Kettlebell (2) and Machine (2) fill the rest. Ten of the 21 are gym-only, more than any other zone.

Structurally it is hinges, holds and stretches. Deadlift variants on barbell, trap bar and dumbbell; Romanian Deadlifts on barbell, dumbbell, kettlebell, landmine and the Smith machine; Back Extension, Reverse Hyperextension, Superman and Superman Hold; three stretches. Romanian Deadlift at 3 sets of 8–10 is the reference point — “push your hips back with soft knees until your hamstrings pull tight” — and Superman Hold at 3 sets of 20–30 seconds is the version that needs a floor and nothing else.

Symmetry: the zone with no exercises of its own

The odd one out of the six is Symmetry, and the way it is odd is the most useful thing on this page. Its line — “Left equals right. Balance reads as quality.” — describes a comparison rather than a body part.

It scores none of the eight back muscles. No exercise in the corpus claims it as a primary zone. Eight exercises touch Symmetry, all of them as a secondary tag, and not one of them is a plain two-handed, two-legged movement. Six are single-arm rows or single-leg hinges, Bird Dog moves opposite arm and leg together, and the Landmine Romanian Deadlift hinges over an angled bar rather than a straight one.

Those eight span three other zones. Four sit in Upper Back (One-Arm Dumbbell Row, Single-Arm Cable Row, Kettlebell Single-Arm Row, Meadows Row). Three sit in Lower Back (Single-Leg Romanian Deadlift, Landmine Romanian Deadlift, Bird Dog). One sits in Lat Width: the Commando Pull-up, where you “alternate which shoulder passes the bar each rep.”

So Symmetry is not a body part. It is a way of doing the other five zones’ work. One-Arm Dumbbell Row spells out the whole principle in one cue — “keep your hips square, and row without twisting your torso” — and Bird Dog, at 2 sets of 8–10, is the only movement in the group prescribed at two sets rather than three, with instructions to “keep your hips dead level, and pause a second before switching sides.”

The score itself is a comparison, not a measurement: your left side against your right side, in the same photo, under the same light. It says one side currently reads bigger than the other and gives you a reason to run the set on your weaker side first. It is not a finding about your body, and it never becomes one.

Zones vs muscles: what the difference actually is

Muscles are anatomy. Zones are the unit you train, score and compare in. The two do not line up one-to-one, and knowing where they diverge is what keeps a plan from drifting.

Three asymmetries fall out of that table. Upper Back carries three muscles, so a single number is hiding three different jobs. Symmetry carries none, so it can never be the answer to “what should I train”. And Rear Delts is the only name that is both a zone and a muscle, which is why it is the one place the two vocabularies can be used interchangeably without losing anything.

The muscle tags across the corpus are lopsided in a way the zone counts hide. Lats appear on 38 of the 77 exercises, Erectors on 23, Rhomboids on 22, Lower Traps on 18, Teres Major on 17, Rear Delts on 16, Upper Traps on 12 and Infraspinatus on 8. A plan built muscle-by-muscle would spend most of its volume on the lats simply because that is where the movements are.

That is the practical case for zones over muscles. A photo cannot see a rhomboid, but it can see thickness between the blades. A session cannot be built around a posterior deltoid, but it can open with a movement that leads with Rear Delts. Zones are what a camera can score and what a week can be built around — the muscle-level breakdown, with each muscle’s own training note, is at the eight back muscles map.

Which zone to prioritize first

Train your lowest-scoring zone. That is the whole rule, and it is what the app does automatically — the plan is generated from your weakest zones rather than from whichever movement you like most. What follows is what to do when your scores do not make the choice obvious.

Upper Back appears in the lead rotation of all five focus programs. Lat Width leads two, Rear Delts appears in three, Traps and Lower Back in one each, and Symmetry in none. If your scores are flat and you genuinely cannot pick, thickness is the default the programming already agrees with.

If your two lowest are Lat Width and Upper Back, you are standing at the width-versus-thickness fork, and both roads are four weeks long: V-Taper Sprint or Thickness Block. Pick by what you want first, since the loser of that decision leads the second month.

Points come cheapest from Traps and Rear Delts. Eight primary exercises each, nothing rated advanced in either block, and 11 of those 16 movements listed as home-viable. Lat Width and Lower Back are the long games: 21 exercises each, eight advanced entries between them, and the two blocks with the most gym-only movements.

Symmetry can never be prioritized on its own, because there is nothing to prioritize. You serve it by substitution — swap a two-handed row for One-Arm Dumbbell Row, a Romanian Deadlift for the Single-Leg version — which is why it never appears as a lead zone in any of the five focus programs. Then re-scan and see whether the number moved.

What a zone score is, and what it is not

One photo of your back, taken with the selfie camera and a 5-second self-timer, produces all six zone scores plus the eight muscle scores underneath them. An AI vision model reads the image; the image is analyzed transiently and never stored on a server, and your before-and-after photos stay on the device.

What comes back is a visual estimate built to aim your training. It reads size, shape and how the two sides compare in that particular photo, under that particular light, at that particular angle. Change the light and the number moves a little, which is why the weekly re-scan matters more than any single result.

Which means the absolute number matters less than the ordering it produces: which of the six is furthest behind today, which program leads with that zone, and whether the score is higher next week than it was this week. Train the bottom of the list, re-shoot, read it again.

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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