Dumbbell Flyes: How I Do Them and What They Actually Do

We’ve all seen Pumping Iron: Arnold lying across the bench, stretching that massive chest with two dumbbells, each arm looking as if it is about to touch the floor. His chest looks ready to rip apart at the bottom, and he has that iconic Arnold training face.

But what is the exercise actually doing?

That exercise is the dumbbell flye. It trains the chest through the action of bringing the upper arms across the body, while also loading the pecs in a stretched position as the arms move apart.

It is also one of those exercises that can truly humble you.

I can dumbbell press the 50s for sets of ten. Put me on flyes, though, and anything above the 22s begins to feel unholy. It quickly tells you whether you genuinely need that weight or whether your ego has taken control of the session.

If you are still learning how to get heavy dumbbells into position safely, read my dumbbell press setup and technique guide first. The initial setup is almost identical.

What do dumbbell flyes actually work?

The main muscle working is the pectoralis major: the large chest muscle responsible for bringing the upper arm across the body. The front deltoids and other muscles around the shoulder also help to control and stabilise the movement.

A flye is different from a press because the bend in the elbow stays almost fixed. You are not trying to push the dumbbells away by straightening the arms. You are opening and closing the arms through a wide arc.

That longer lever is one reason flyes feel so much heavier than the number printed on the dumbbell. It is perfectly normal to flye considerably less than you can press. This is not an exercise on which I chase numbers for the sake of it.

How I set up for dumbbell flyes

For this example, I would start with the 18 kg dumbbells.

I sit on the bench with both dumbbells resting on my knees. I then use my knees to help kick them up one at a time before pressing them into the starting position above my chest.

Once I am lying back, I set my upper back against the bench and keep my shoulder blades controlled. I want a stable base underneath me, with the tension going through my chest rather than my shoulders fighting to keep everything together.

The easiest way I imagine the movement is that I am hugging a large tree.

I begin with the dumbbells above my chest in a neutral grip—the same hand position you would use for a hammer curl. The dumbbells are close together, but they do not need to smash into one another.

My elbows have a slight bend in them. That bend stays nearly fixed throughout the repetition. If I keep bending and straightening my elbows, I am no longer really performing a flye; I am turning it into a press.

Lowering the dumbbells

As I lower the weights, I deliberately draw a wide arc with my arms.

I imagine there is a piece of string running from one elbow to the other. I want to keep that shape consistent as both arms move away from one another. The hands are carrying the dumbbells, but mentally I am controlling the movement through my elbows.

I continue lowering until I feel a strong but controlled stretch across my chest.

This is where choosing the correct weight becomes important. Some people are naturally more mobile and can lower the dumbbells farther than others. That does not mean everyone should copy Arnold and try to reach the floor.

My usual target is to let my elbows travel slightly below the level of my torso, but only while I can keep the position controlled and pain-free. If my shoulders roll forwards, the dumbbells drop, or I feel a sharp sensation at the front of the shoulder, I have gone too deep or chosen too much weight.

Research generally supports training through a useful, controlled range of motion, but “more range” is not automatically better when it exceeds the range you can own. A systematic review found that full-range resistance training often produced favourable strength and muscle adaptations, although the evidence was not specific to dumbbell flyes.¹

You do not receive extra points for taking your shoulders somewhere they do not want to go.

Bringing the dumbbells back up

Once I reach the bottom and feel the stretch, I reverse the movement along the same path.

This is where my imaginary string comes back into play.

Instead of thinking about bringing my hands together, I imagine that I am trying to bring my elbows towards one another. They will never actually meet because my arms remain slightly bent, but that intention helps me drive the movement through my chest instead of simply moving the dumbbells from A to B.

At the top, I squeeze my chest without allowing my shoulders to lift away from the bench. Then I begin the next repetition, following the same controlled line down and back up.

This is the movement in simple terms: keep a soft bend in the elbows, lower through a wide controlled arc, stop at the deepest position you can own, then bring the upper arms back across the body and squeeze the chest.

That focus on what the target muscle is doing is similar to the approach I explain in my bench press technique guide. The exercise changes, but the principle of controlling the position does not.

Flat versus incline dumbbell flyes

The path changes slightly depending on the angle of the bench. On an incline bench, my arms travel across a slightly higher line. On a flat bench, they travel more closely in line with the middle of my chest.

Research using pressing movements has found that changing the bench angle alters the activation of different regions of the pectoralis major and the front deltoid.² That does not prove that every tiny change in a flye isolates a completely separate piece of chest, but it does support the basic idea that bench angle changes how the movement loads you.

I use incline and flat flyes as variations, not as two completely different exercises.

The variations I use

One of the things I enjoy about dumbbells is that they do not lock me into one fixed hand position.

On some days, I keep the dumbbells in almost exactly the same position from the beginning of the repetition to the end.

On other days, I allow a small and controlled rotation as I lower and raise them. I might finish with my thumbs angled slightly towards one another at the bottom before rotating back towards neutral as I return to the top.

Sometimes I begin with my arms in a position closer to a dumbbell press and then open them into the flye. That creates a press-flye hybrid and normally allows a little more weight.

These changes can alter where I feel the exercise and may make one position more comfortable than another. What I would not claim is that turning my wrists magically isolates one tiny “bottom-middle” section of the chest. The chest is still performing the same basic action. The change is mainly affecting the angle, leverage and feel of the movement.

Any rotation should be small and natural. I do not force my wrists or shoulders into an extreme position while holding heavy dumbbells just because I felt a slightly different squeeze once.

Do not let your ego choose the weight

The dumbbell flye is not meant to look like a maximum-effort press.

If my elbows keep bending, the dumbbells fall uncontrollably, or I can only perform half of the range I intended to use, the weight is too heavy. I reduce it until I can control the descent, feel the stretch and return through the same arc.

The goal is not to prove how much I can flye. The goal is to place my chest under useful tension without asking my shoulder joint to rescue a badly controlled repetition.

Progress does not always mean jumping to the next pair of dumbbells. It can mean cleaner repetitions, a more consistent range, an extra rep with the same weight or better control at the bottom. I explain that wider idea in my guide to progressive overload.

The American College of Sports Medicine recommends progressing resistance training systematically rather than increasing load without regard for technique or the lifter’s current ability.³

Experiment—but experiment intelligently

My point with all of these guides is to experiment.

Do what works for your structure. Use your imagination to understand the movement. Listen to experienced people, but also pay attention to what your own muscles and joints are telling you.

A small change in bench angle, elbow position or grip can make an exercise feel completely different. That freedom is one of the biggest advantages dumbbells give you.

But experimenting does not mean forcing painful positions or adding weight for the sake of it. Keep the movement controlled, respect your shoulders and let your chest do the work.

Do that, and you will not be too far away from what you need.

References

1. Schoenfeld BJ, Grgic J. Effects of range of motion on muscle development during resistance training interventions: a systematic review. SAGE Open Medicine. 2020.
2. Lauver JD, Cayot TE, Scheuermann BW. Influence of bench angle on upper extremity muscular activation during bench press exercise. European Journal of Sport Science. 2016.
3. American College of Sports Medicine. Progression models in resistance training for healthy adults. Medicine & Science in Sports & Exercise. 2009.

This article describes my personal training method and is for general education only. If an exercise causes pain, stop and seek guidance from an appropriately qualified professional.