What muscles does the rear delt fly work?

The rear head of the deltoid does the work. The traps and rhomboids assist by holding and pulling the shoulder blades. If your upper back is what feels worked instead of the back of your shoulders, those assisting muscles have taken over the movement.

Should you squeeze your shoulder blades together on a rear delt fly?

No, and this is the most repeated bad cue on the movement. Squeezing the blades together is a separate action driven by the rhomboids and mid traps, which are stronger and will happily do the job for you. Move the upper arm at the shoulder and leave the blades alone.

Why do I feel rear delt flies in my traps?

Almost always because the weight is too heavy, so your shoulders shrug upward to help lift it. It can also come from squeezing the shoulder blades together rather than moving the arm. Both problems get smaller with a lighter dumbbell.

How should you hold the dumbbells for a rear delt fly?

Palms facing each other. When 19 resistance-trained men were compared across hand positions on this arm path, the neutral hand produced more rear-shoulder activity than turning the palms down.

Can you do rear delt flies seated?

Yes, and sitting on the end of a bench and hinging forward from there is often the better version. It gives the hinge something to rest against, so the position holds for the whole set rather than drifting upright as you tire.

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Dumbbell · beginner · back

Dumbbell rear delt fly

Also called Reverse fly, Bent over fly, Rear delt raise, Reverse dumbbell fly, Bent-over lateral raise.

The short answer

The rear delt fly is done bent over, opening the arms out and back until they are level with the floor. The rear head of the deltoid is the muscle it is built around, and pressing barely reaches it, which is why the movement exists. Your traps and rhomboids assist by pulling the shoulder blades together, and the main thing that goes wrong here is letting them lead instead.

How to do it

Step oneStand with your feet hip-width apart and hinge forward at the hips until your chest is close to horizontal.
Step twoHold a dumbbell in each hand with a neutral grip, allowing them to hang beneath your shoulders.
Step threeRaise the dumbbells out to the sides in a wide arcing motion, moving your upper arms at the shoulder and leaving your shoulder blades where they are.
Step fourPause at the top when your arms are parallel to the floor.
Step fiveSlowly lower the dumbbells back to the starting position.

What usually goes wrong

Each starts with what you would notice.

You feel it between your shoulder blades and across your upper back, not at the back of your shoulders.

WhyYou are squeezing the shoulder blades together, which is a different movement at a different joint. Pulling the blades toward each other is the job of the rhomboids and mid traps. They are bigger and stronger than the rear delt, so once they lead, the muscle you came for gets very little.

FixThink about moving your upper arm, not your shoulder blade. Let the blades stay where they are and sweep the arms out and back at the shoulder. It will feel like less work, because it is being done by a much smaller muscle.

Your shoulders ride up toward your ears as you lift.

WhyThe traps are helping the arms get to the top, which almost always means the dumbbells are heavier than the rear delt can raise on its own.

FixLighten the load until the shoulders stay down and the arms do the traveling. This is a very small dumbbell exercise and there is no version of it where that changes.

Your elbows bend on the way up and it feels like a row.

WhyA bending elbow lets the biceps and lats pull, so the weight arrives at the top without the rear delt having moved much.

FixFix a slight bend at the elbow before you start and hold that exact angle to the top and back. The distance from your hand to your shoulder should never change.

By the last reps you are standing more upright than when you started.

WhyThe torso is creeping up, and as it does the arms stop traveling backward relative to your body and start traveling sideways.

FixSet the chest close to your thighs and check it every few reps. If you cannot hold the hinge for the whole set, sit on the end of a bench and hinge from there.

Rear delt fly or rowing

Both work the back of the shoulder, and people ask which is enough on its own. The two look similar and are doing different things.

A row brings the elbow back close to your ribs, with the lats and biceps pulling and the shoulder blade retracting. A fly keeps the arms wide and moves the upper arm at the shoulder joint with nothing else contributing.

The evidence does not settle it. Reviews that pooled the shoulder studies put pull-ups and rows at the top for the rear head. A study comparing a machine reverse fly against a seated row put the fly ahead. Both agree the rear head needs pulling work of some kind, which is the part that matters. If you row and never fly, you are not neglecting it.

Rear delt fly or lateral raise

These are the same arm path with your torso in a different place, and noticing that makes both movements easier to understand.

Standing upright, raising the arms out to the sides moves them away from your body sideways, and the middle head of the shoulder does that.

Bent over with your chest near your thighs, the same arm path now moves your arms backward relative to your body. That is the rear head. So the angle of your torso is not a detail here, it is what decides which head you are working. A half-hearted hinge gives you a half-hearted rear delt exercise.

Posture is not something this page can assess

This movement gets sold as a posture fix. Rounded shoulders from sitting at a desk, that story. We are not going to make that claim, because nothing in the research supports it and posture is not something a page can assess from here.

What is fair to say is anatomical and much smaller. Every press works the front of your shoulder. Nothing you press works the back of it. If your training is presses and curls, the rear head is getting nothing, and this movement or a row is how that changes.

This is never going to be an exercise you load heavily. The rear delt is small, the arm is long, and this puts the two together in the worst possible arrangement for lifting weight. A dumbbell that looks embarrassing is the right dumbbell here.

What it is for

The rear delt dumbbell fly is an exercise targeting the posterior deltoid, with the trapezius and rhomboids retracting the shoulder blades. Performed bent over, it trains the muscles responsible for scapular retraction and rear shoulder development.

Questions people ask

What muscles does the rear delt fly work?: The rear head of the deltoid does the work. The traps and rhomboids assist by holding and pulling the shoulder blades. If your upper back is what feels worked instead of the back of your shoulders, those assisting muscles have taken over the movement.
Should you squeeze your shoulder blades together on a rear delt fly?: No, and this is the most repeated bad cue on the movement. Squeezing the blades together is a separate action driven by the rhomboids and mid traps, which are stronger and will happily do the job for you. Move the upper arm at the shoulder and leave the blades alone.
Why do I feel rear delt flies in my traps?: Almost always because the weight is too heavy, so your shoulders shrug upward to help lift it. It can also come from squeezing the shoulder blades together rather than moving the arm. Both problems get smaller with a lighter dumbbell.
Is the rear delt fly better than a row for rear delts?: Nobody has settled it. Reviews pooling the shoulder research rank pull-ups and rows highest for the rear head, while a study comparing a machine reverse fly against a seated row favored the fly. What all of it agrees on is that the back of the shoulder needs pulling work, and presses do not provide it.
How should you hold the dumbbells for a rear delt fly?: Palms facing each other. When 19 resistance-trained men were compared across hand positions on this arm path, the neutral hand produced more rear-shoulder activity than turning the palms down.
Can you do rear delt flies seated?: Yes, and sitting on the end of a bench and hinging forward from there is often the better version. It gives the hinge something to rest against, so the position holds for the whole set rather than drifting upright as you tire.