Pull-Up Muscles: Lats, Arms, and Core Phase by Phase, and What to Check When You Don't Feel It in Your Back (2026)

2026.10.19

The pull-up muscles don't stop at the lats in your back. Even within a single rep, the muscles doing the most work change from one phase to the next, and the muscles of your arms and trunk send out signals too. This post splits one rep into phases, lays out what anatomy references say each muscle does and what ranges the research measured, and then covers what to check in your form when you don't feel it in your back.

The anatomy follows StatPearls, a medical reference whose chapters are each listed on PubMed. The research comes in two kinds. One is electromyography (EMG), which picks up a muscle's electrical signal with electrodes on the skin. The other recorded the movement with cameras and a force plate, then used a computer model of the shoulder to calculate how much force each muscle produced (Urbanczyk et al., 2020). Both looked at the movement as it was being done, not at how muscles change after a period of training. How grip changes things is covered separately in the chin-up vs pull-up post.

Pull-up muscles at a glance: what shows up in each phase #

The movement column is based on the pull-up guide in the ACE (American Council on Exercise) exercise library. The muscle column draws on a mix of sources, so each phase is unpacked below. In particular, the two studies disagree on when the biceps and lats work hardest. In the EMG study (Youdas), they were recruited toward the finish of the movement; in the model (Urbanczyk), they worked mainly through the middle range (see the lats section below).

The hang: your hands and forearms on the bar #

Once your feet leave the floor, your two hands hold your entire body weight, unless a band or a foot support is helping. StatPearls describes twenty forearm muscles split between two compartments, front (flexor) and back (extensor), and notes that they move not only the elbow and wrist but the finger joints as well. If your hands give out first when you hang, see the pull-up grip post, which covers thumb position and bar thickness.

Start of the pull: the trapezius lowers your shoulder blades, and other muscles drive your upper arms down #

The trapezius is a large back muscle that runs from the back of your skull (the occipital bone) down to the lower thoracic vertebrae, and out to the side as far as the spine of the shoulder blade. StatPearls says its job is to stabilize and move the shoulder blade: the middle fibers pull the shoulder blade inward (retraction), and the lower fibers pull it down (depression). ACE's guide tells you to set your shoulders in the starting position and hold them there for the whole movement, and its exact wording is "depress and retract your scapulae (pull shoulders back and down)." Those are the same two jobs StatPearls gives the lower and middle fibers.

The research also puts the trapezius at the start. Youdas et al. (2010) used EMG on 21 men and 4 women to compare when each muscle's signal peaked, and reported a general sequence: the movement began with the lower trapezius and pectoralis major and finished with the biceps and lats being recruited. In Urbanczyk et al. (2020), which ran the model on 11 men who had been training pull-ups for more than three years, the trapezius, infraspinatus, and brachialis were under relatively more stress early in the movement. At the starting position, with the upper arm raised high overhead, the lats, posterior deltoid, and teres major were the prime movers, pulling the upper arm down and lifting the trunk.

The infraspinatus fills much of the hollow below the spine of the shoulder blade. It is one of the four rotator cuff muscles, a group that allows a wide range of motion while keeping the shoulder joint stable. The brachialis is an elbow flexor that sits deeper than the biceps. Keeping your shoulders down while you hang, instead of letting them ride up toward your ears, comes up in the post for when you can't do a pull-up.

The lats in a pull-up: the broad muscle that pulls your upper arm down toward your trunk #

The latissimus dorsi (lats) is a broad, flat muscle covering most of the lower back of the rib cage, and StatPearls gives its main job as moving the arm. The teres major, which runs from the lower back of the shoulder blade to the upper arm bone, works together with the lats to extend the upper arm, bring it in toward the body (adduction), and rotate it inward (internal rotation). A 2026 review that gathered EMG studies of the lats in pulling exercises (Di Fonza et al.) also treats the lats as the primary muscle in pulling exercises.

In the Youdas study, the lat signal came in at 117 to 130% across all three exercises (a pull-up, a chin-up, and a pull-up on rotating handles), the highest range of any muscle measured. The percentage is relative to the peak signal from a test where you hold a maximal effort in place, so a value above that reference means the signal during the pull-up was bigger than during that test. The two studies paint different pictures of when the lats work hardest. In the EMG study (Youdas), they were recruited toward the finish of the movement. In the model (Urbanczyk), they were a prime mover from the start and did most of their work through the middle range.

The biceps is a large, thick muscle on the front of the upper arm, and StatPearls describes it as a muscle that bends the forearm when the arm is straight. In the Youdas study, the biceps signal was 78 to 96%, second only to the lats. In the Urbanczyk model, though, across all three grips, bending the elbow was secondary to bringing the upper arm toward the trunk.

The top: triceps, subscapularis, and reps that go all the way up #

In the Urbanczyk model, the muscles that became most active toward the end of the upward movement were the triceps and the subscapularis, and the paper credits the triceps with fully extending the upper arm at the top. The triceps sits on the back of the upper arm, and its main job is straightening the elbow. Of its three heads, the long head starts on the shoulder blade. The subscapularis, like the infraspinatus, belongs to the rotator cuff.

The same paper concludes: "To maximize the benefit of pull-ups, performing the task over its full range of motion is important as different portions of the task emphasize different muscles." A rep that stops before your chin reaches bar height skips the top portion, and a rep that doesn't straighten your arms at the bottom skips the start.

PULL UP KING counts reps where your chin crosses the judging line (a dashed line just below the bar, around elbow height). The line sits below the bar on purpose, because camera angle and joint detection carry some error, so a rep where your chin stops a little short of the bar still counts once it crosses the line. The app also doesn't judge whether your arms fully straightened at the bottom or whether you used momentum. Whether you went all the way from end to end is something to check separately, on video filmed from the side, as the pull-up form post also suggests.

The way down: the same muscles resist as they lengthen #

When a muscle lengthens while producing force, that's called eccentric; when it shortens, it's concentric. A review by Proske and Morgan (2001) puts it this way: concentric contractions start movements, and eccentric contractions slow or stop them. On the way down in a pull-up, your elbows straighten, so the muscles that bend the elbow move in the lengthening direction.

Dickie et al. (2017) recorded EMG from eight muscles of the shoulder, arm, and forearm in 19 strength-trained men doing four pull-up variations (underhand, overhand, and neutral grips, plus a rope pull-up). In all four, the average signal of the brachioradialis, biceps, and pectoralis major was significantly higher on the way up than on the way down. The brachioradialis is a forearm muscle that works as a flexor. The signal doesn't disappear on the way down, though. When Doma et al. (2013) measured chin-ups, biceps and lat signals during the lowering phase were higher than the triceps signal.

In PULL UP KING, switch on Analysis in a set's video window and the app times how long each rep takes to come down from the top to the bottom, measured over the middle 80% of the movement. If the median of those times is under 0.55 seconds, the coach says: "You drop on the way down. Lowering is part of the rep — stay in control and come down slowly." The Analysis button only shows up on sets that can be analyzed. Training just the lowering half on its own is covered in the negative pull-ups post.

Your trunk: bracing your abs and not swinging #

ACE's guide has you gently cross one leg over the other and brace your abs to stabilize your spine, then pull while keeping your body vertical to the floor, without swinging. In the Youdas study, the erector spinae produced signals of 39 to 41%, and the external oblique 31 to 35%.

Add momentum, and the signals get distributed differently. Dinunzio et al. (2019) had 11 athletes do 5 standard pull-ups and 5 kipping pull-ups, which add a gymnastics glide kip to the standard pull-up. In the kipping version, signals from the rectus abdominis, external oblique, iliopsoas, and tensor fasciae latae went up, by 13.5 to 28.7 when expressed as a percentage of maximal contraction, while the biceps signal went down by 26.7 on the same scale. The authors write that you may choose the standard pull-up for higher upper-body muscle activation.

Not feeling the pull-up muscles in your back: what to check in your form #

First, separate what you feel from what was measured. EMG records an electrical signal, not a sensation, and Urbanczyk et al. also write that EMG is useful for showing the pattern of muscle activation but is susceptible to cross-talk and a poor indicator of absolute activation levels. Your arms working along with your back is part of this movement, too. ACE lists the pull-up's target body parts as arms and back, and in the Youdas study the biceps signal was second only to the lats. If you're feeling pull-ups in your arms first, nothing in the sources for this post supports concluding from that alone that your back isn't working. With that in mind, there are two places to check.

Start by pulling your shoulder blades down #

Step 1 of ACE's guide has you depress and retract your shoulder blades and hold that position throughout the exercise, and pulling the shoulder blades down is the job of the trapezius's lower fibers. If your shoulders ride up toward your ears as you pull, start here. PULL UP KING's set analysis uses this cue too: on a set where the coach says "On the way up, you drift to the screen’s left (or right)," it adds "Shoulder blades down first, then both elbows to your sides, evenly."

Drive your elbows down toward the floor #

ACE tells you to pull in a motion that drives your elbows straight down toward the floor, and for the pull-up, to keep your elbows lined up with the sides of your trunk, at the 3 and 9 o'clock positions. There is a study where verbal instructions changed a muscle's signal, but it used the lat pulldown. In Snyder and Leech (2009), 8 women with little or no strength training experience did lat pulldowns at 30% of their max, and after being told verbally how to emphasize the lats and de-emphasize the biceps, their lat signal rose significantly. Biceps and teres major signals didn't change, and the authors wrote that the increase probably did not represent "isolation" of the muscle group. Since this was a lat pulldown with a light weight, it can't be carried straight over to bodyweight pull-ups.

Not swinging and going all the way from end to end are covered in the trunk and top sections above. If your shoulders, elbows, or wrists hurt anywhere while you pull, stop there for the day.

FAQ #

Are pull-ups a back exercise or an arm exercise? #

Both work. ACE lists the target body parts as arms and back, and says the exercise "targets the back muscles effectively." In the Youdas study, the lats had the highest signal range, followed by the biceps. The ranking isn't the same in every study, though: Urbanczyk et al. note that Doma et al., who measured chin-ups, found biceps activation slightly larger than lat activation.

Do pull-ups and lat pulldowns use the same muscles? #

They overlap, but they aren't the same. In Doma et al. (2013), which compared chin-ups with lat pulldowns, biceps and lat signals during the pulling phase were higher than the pectoralis major in both exercises, and in that same phase, biceps and erector spinae signals were higher in the chin-up than in the lat pulldown. And because the lat pulldown is done sitting down, it doesn't train the part where you hang from the bar and hold your body weight.

Do chin-ups and pull-ups work different muscles? #

The studies split. In the Youdas study, the pectoralis major and biceps signals were higher in the chin-up and the lower trapezius signal was higher in the pull-up, but in the Dickie study, muscle activity across a full rep was similar despite different hand orientations. A 2026 review that brought together 23 EMG studies across six pulling exercises sums up that, among them, pull-up variations showed broadly similar lat activation across grips.