Functional Anatomy of the Back: Lats, Traps, Rhomboids, Teres and Erectors

The simplest way to understand back muscles anatomy in functional terms is to split the back into three jobs. The lats pull your arm down and back, the rhomboids and middle and lower traps pull your shoulder blade toward your spine, and the erector spinae hold your spine upright. Once you know which muscle does which job, picking back exercises stops being guesswork.

This article is the anatomy map for our complete back training guide. We will cover where each muscle attaches, which way its fibers run, and how your arm path changes what a row or pulldown asks of you. The goal is practical: after reading, you should be able to look at an exercise and say which part of the back it is built for.

What are the main back muscles and what do they do?

Anatomy textbooks list dozens of muscles on the back. For training, six groups matter most.

Muscle	Attaches (roughly)	Main job	Typical exercises
Latissimus dorsi	Lower spine, pelvis, lower ribs to front of upper arm bone	Arm down and back, toward the body	Pulldowns, pull-ups, rows
Teres major	Lower edge of shoulder blade to upper arm bone	Same direction as lats	Any pulldown or row
Upper trapezius	Skull and neck to collarbone and shoulder	Lift and rotate the shoulder blade	Shrugs, carries
Middle trapezius and rhomboids	Spine (neck to mid-back) to shoulder blade	Pull the shoulder blade toward the spine	Rows with flared elbows, reverse flys
Lower trapezius	Mid and lower thoracic spine to shoulder blade	Pull the blade down	Low-angle pulls, Y-raises
Erector spinae	Pelvis and sacrum up the spine to the ribs and skull	Extend and brace the spine	Deadlifts, back extensions

The origins and insertions above are standard anatomy. I have kept them simple on purpose: the point is the direction each muscle pulls, not memorising Latin.

Latissimus dorsi: the big diagonal sheet

The lat is the widest muscle of the back. It starts from the spinous processes of the lower thoracic and lumbar vertebrae, the back of the pelvis and the lowest ribs, then sweeps up and outward to insert on the front of the upper arm bone. Most of that low attachment goes through the thoracolumbar fascia, a sheet of connective tissue across the lower back. A 2012 anatomy review notes that the superficial layer of this fascia is dominated by the aponeuroses of the latissimus dorsi and serratus posterior inferior (Willard et al., 2012).

What this means for you:

• Functionally, the lat links your arm to your pelvis. That is why it matters in pulling, climbing and even throwing.
• Its actions are shoulder extension, adduction and internal rotation. A 2026 narrative review of lat EMG studies describes it in those terms (Di Fonza et al., 2026).
• The fibers run diagonally, so the cleanest line of pull is the arm moving down and back toward the hip, not straight back at shoulder height.

If you want the finer detail on how different parts of the lat attach, our article on regional lat anatomy goes deeper.

Teres major and minor: the small neighbours

The teres major sits right next to the lat and travels with it. It runs from the lower outer edge of the shoulder blade to the upper arm bone, so it does a similar job (pulling the arm down and back). It gets worked in almost every pulldown and row. The teres minor is different: it is a small rotator cuff muscle that rotates the arm outward, and it matters more for shoulder health than size. We cover both in teres major and minor anatomy.

Trapezius: three muscles in one

The trapezius is a big kite-shaped muscle that is better thought of as three muscles. A 2019 review describes it as a dominant stabilizer of the scapula that is divided into upper, middle and lower parts, each of which can be targeted with different exercises (Camargo and Neumann, 2019).

• Upper traps run from the skull and neck to the collarbone and shoulder. They lift the shoulder blade (shrugs, carries).
• Middle traps run horizontally from the upper thoracic spine to the shoulder blade. They pull it back toward the spine.
• Lower traps run from the mid and lower thoracic spine up to the shoulder blade, which makes them the main muscles for pulling it down.

Rhomboids: the muscle under the trap

The rhomboids sit under the trapezius, running from the spine (lower neck to mid-back) down and outward to the inner edge of the shoulder blade. They pull the shoulder blade toward the spine and help hold it flat against the ribs. In practice they work alongside the middle traps, and you cannot reliably isolate one from the other in training.

Erector spinae: the spine’s own cables

The erectors are three vertical columns of muscle on either side of the spine (iliocostalis, longissimus and spinalis). They start low on the pelvis and sacrum and run up toward the ribs and skull. Their job is to extend the spine and resist it flexing forward, so any time you hold a hinged position under load, they are working.

A 2020 systematic review of deadlift EMG reported that the erector spinae and quadriceps were more activated than the gluteus maximus and biceps femoris across deadlift variations, with the Romanian deadlift showing lower erector activation than hamstring activation (Martin-Fuentes et al., 2020). The authors also point out that methods vary between studies, so treat the comparisons as general.

How does arm path change which back muscle works?

This is where anatomy becomes useful. Because muscles pull along their fibers, the path of your elbow decides which fibers get a good line of pull.

• Elbow down and toward the hip lines up with the lat’s diagonal fibers. Pulldowns, pull-ups and close-grip rows live here.
• Elbow out level with the shoulder moves the arm along a horizontal path that suits the middle traps, rhomboids and rear delts, which is why flared-elbow rows and reverse flys feel more “upper back”.

The evidence for this is suggestive, not settled. The 2026 narrative review of lat EMG found that in the seated row, a narrower grip and a lower shoulder abduction angle were each linked to higher lat activity in separate studies, but these two variables have not been tested together. It also concluded that the relationship between the upper arm and the trunk may be a key factor for how load spreads across muscles. Those are acute EMG results, not long-term growth results, and the review recommends treating them as a starting point (Di Fonza et al., 2026). Our article on lats versus upper back and elbow flare takes this further.

Does grip width change lat activation?

Less than most gym advice suggests.

Lusk and colleagues tested 12 men on four lat pulldown grips (wide or narrow, pronated or supinated) at 70% of 1RM and found the pronated (overhand) grip produced greater lat activity than the supinated grip, regardless of width (Lusk et al., 2010).

Andersen and colleagues tested 15 men at narrow, medium and wide pronated grips (1, 1.5 and 2 times shoulder-bone distance). The 6RM load was a little lower with the wide grip (about 77 kg versus 80 kg), and lat activation was similar across grips overall, with greater lat activation for wide versus narrow only in the eccentric (return) phase (Andersen et al., 2014). The authors concluded that similar hypertrophy should be expected from grip widths between 1 and 2 times shoulder-bone distance.

Why might the two studies differ a little? They used different loads, different grip definitions and small samples of young men, so findings may not carry over to everyone. The practical takeaway: pick a grip you can pull with your elbows, not your hands, and stop obsessing over centimetres. For a full comparison see wide vs close vs neutral grip pulldowns.

Which row works which muscles, and what does it cost your spine?

Different rows also load the spine differently. Fenwick and colleagues instrumented 7 healthy men to compare an inverted row, a standing bent-over row and a standing one-arm cable row. The inverted row produced the highest activation of the lats, upper back and hip extensors, with lower lumbar erector activation and the lowest spine load. The bent-over row gave large activation across the whole back but the highest lumbar load. The one-arm cable row challenged trunk twisting strength (Fenwick et al., 2009).

This was a small study of young, healthy men, so it cannot tell you how a given lifter should train. But it fits how most coaches already think: if your lower back is your limiting factor, use a chest-supported or inverted variation.

How to use this anatomy in your training

1. Pick the job first. Want lat width? Choose pulls where the elbow travels down and back. Want the upper back? Choose pulls where the elbows travel out and the shoulder blades finish pulled back.
2. Match the cue to the muscle. “Elbows to hips” for lats. “Shoulder blades together” for the retractors. For details on retraction and depression cues, see scapular retraction vs depression.
3. Use both a vertical and a horizontal pull each week. They overlap, but not completely.
4. Respect the spine. The erectors are working in most heavy rows and hinges, so manage total volume.
5. Check for pain. Sharp, radiating or lingering pain is not a training problem to push through. See a doctor or physiotherapist.

The bottom line

The back is easier to train once you see it as three jobs: lats for pulling the arm down and back, scapular retractors for moving the shoulder blade toward the spine, and erectors for holding the spine. Your elbow path is the main control knob, and grip width matters less than it looks. Treat the EMG findings as helpful starting points, not rules, since most are acute studies in small samples of healthy young men.

Next, apply it: run our pull day plan and work out your daily protein with the protein calculator.