Rear delt fly: dumbbell, cable or machine, and how to keep it a fly

A rear delt fly, also called a reverse fly, sweeps your arms out and back in a wide arc: the chest fly run in the other direction. It's done bent over with dumbbells, on a cable station, or seated facing the pad of a reverse pec deck. The target is the rear head of the shoulder, the part of the deltoid that takes the arm back, both down at your side and out at shoulder height,¹ with help from the muscles across the upper back.

This page covers the three setups, the arm path and the grip, what the studies measured, the faults, and how the fly fits a shoulder day. The full session for all three heads of the shoulder is on the shoulder workout, and the cable pull toward your face that works the same area is on face pulls.

Three ways to set it up

Dumbbells, bent over

1. Hinge forward from the hips until your chest is close to parallel with the floor, back flat and knees soft. Or lie chest-down on a bench set to a low incline.
2. Let the dumbbells hang under your shoulders, palms facing each other, elbows slightly bent.
3. Sweep your arms out and back until your upper arms line up with your body, holding the same slight bend at the elbow the whole way.
4. Lower in about two seconds until the dumbbells are back under your shoulders, then start the next rep.

The machine: a reverse pec deck

Sit facing the pad with your chest against it. Set the seat so the handles are at shoulder height, and set the handles so they start in front of you with your arms nearly straight. Push them out and back in an arc until your arms line up with your shoulders, then let them return slowly, without letting the weight stack touch down between reps.

Cable or band

Set two pulleys at about shoulder height and stand between them. Cross the cables in front of you, the left handle in your right hand and the right handle in your left, and sweep your arms out and back. On a single pulley, stand side-on, hold the handle in the hand farther from the pulley, and sweep that arm across and back. No study comparing a cable rear delt fly with the dumbbell or machine version turned up in a PubMed search for this page. With no cable at all, a band pull-apart is the same movement: a band held in front of you at shoulder height with straight arms, pulled apart until it touches your chest.

The arm path: a fly, not a row

What separates this exercise from a row is what the elbows do. In a fly, they keep a slight bend and travel out to the sides at about shoulder level. In a row, they bend and pull back toward your ribs. The difference shows up in the studies:

• The machine fly beat two pulls. In 12 men with at least a year of strength training, the reverse pec deck produced more rear-delt activity than a seated row or an inclined lat pulldown.²
• The dumbbell fly beat a row in a model. In a computer-modeling study of 10 healthy men, the bent-over dumbbell raise, the dumbbell version of this exercise, produced an estimated rear-delt force comparable to a standing face pull, with no significant difference between the two, and more than a bent-over dumbbell row.³ That's an estimate from a model, not measured muscle activity or growth.

So hold the bend fixed. If your elbows bend more and drift toward your hips as the set gets hard, the fly has turned into a row, and the weight is too heavy. Stop each rep when your arms line up with your body, rather than forcing them further back.

Grip: palms facing each other or palms down

Most reverse pec decks offer two handle positions, and the two studies that tested hand position point in different directions:

• Palms facing each other came out ahead on the machine. In 19 resistance-trained men on a reverse fly machine, a neutral grip produced more rear-delt and infraspinatus activity than palms facing down.⁴
• Palms down came out ahead with a band. In 10 healthy men doing band pull-aparts, palms down produced the most rear-delt activity of three hand positions, while palms up raised activity in the infraspinatus and the lower trapezius instead.⁵

Different exercises, small groups, opposite answers. On the machine, palms facing each other is the default with the evidence behind it. With a band, palms down has the study behind it; with dumbbells, either grip is reasonable. Pick one, keep it for a block of weeks, and add reps or weight to it.

What the rear delt fly trains

• The rear delt, first: in the 12-man study, the reverse pec deck worked it harder than the row and the pulldown.²
• The side delt, too. In the same men, the middle head of the shoulder was more active in the reverse pec deck and the seated row than in the pulldown.²
• The muscles on the back of the shoulder blade and the upper back. The machine study measured the infraspinatus working alongside the rear delt,⁴ and the band study recorded the upper, middle and lower trapezius working as well.⁵

Two limits on all of this. First, the fly isn't the only rear-delt exercise, or the top one in the activity data: a 2024 review of 33 studies ranked pull-ups highest for the rear head, with the standard pull-up and an inverted row on suspension straps at the top of the list.⁶ If your week already has pull-ups and inverted rows, your rear delts are already working. Second, every study above measured activity during a set, not growth over weeks. No trial that measured rear-delt growth from a reverse fly turned up in a PubMed search for this page. More broadly, a 2023 meta-analysis of 13 studies found no significant difference in muscle growth between free-weight and machine training in the five studies that measured it,⁷ so the machine and the dumbbells are both fair choices.

The common faults, and a fix for each

• Turning it into a row. Elbows bending and pulling toward your hips. Lighten the weight and hold one bend from the first rep to the last.
• Swinging the torso. On the bent-over version, your chest rising with each rep hands part of the lift to your back and hips. Rest your chest on an incline bench, or use the machine.
• Shrugging. Shoulders creeping toward your ears shift the work to the upper trapezius. Think of reaching your hands out to the walls rather than up.
• Going too heavy. The rear delt is a small muscle. The right weight is one you can sweep out 12 to 16 times without the elbows bending.
• Dropping the weight. Lower in about two seconds; on the machine, keep the plates off the stack between reps.
• Training through something that hurts. Sore the next day is normal; a sharp or lasting hurt in the shoulder isn't. Stop, and see a doctor or a physical therapist.

How it fits a shoulder day

• Last, after the presses and the side raises. On the shoulder workout it takes the final slot: two or three sets of about 12 to 16, after the overhead press and lateral raises.
• Close to failure. Like other isolation work, it's a fine place to stop with zero or one rep left. (How to judge reps left.) The American College of Sports Medicine's 2026 position stand, which covers healthy adults, advises at least two sets per exercise.⁸
• Face pull or fly. The face pull can take the fly's slot, or the two can trade places from one block of weeks to the next; they work the same area.
• On an upper-body day, pair it with a press: one set of the chest press machine, then one set of the fly, then rest. The arms come last, with a tricep pushdown and a preacher curl.
• Progress by reps first. Dumbbell and stack jumps are big for a small muscle; add reps inside the range, then take the next weight.

If you'd rather not plan it alone

A rear delt fly is easy to learn; fitting it around your rows, pull-ups and presses so the back of the shoulder gets enough work without crowding everything else is the part a page can't do. Coaching is the version where your workouts are built around the days you actually have, and a weekly call looks at the week you just had and rebuilds the next one. Coaching to build muscle explains how that works, and here's how to apply. Otherwise: at your next shoulder session, add three sets of the fly after your lateral raises and write down the weight.