Reverse Fly

What the reverse fly actually trains

The deltoid is usually described as three heads, but the anatomy is finer than that. Sakoma and colleagues mapped the muscle and described seven functional segments across the anterior, middle and posterior portions, each with its own line of pull. The reverse fly loads the posterior segments, the part that takes the arm out and back.

That matters because almost nothing else in a normal programme does. Overhead pressing hammers the front delt. Lateral raises take care of the middle. Rows involve the rear delt, but they involve it as an assistant to a much larger pulling movement, and the elbow path of a row does not match the transverse abduction that the rear delt is built for.

The result is a predictable imbalance. People who press a lot and row a little end up with a shoulder that is well developed at the front and thin at the back. The reverse fly is the cheapest available fix, and it costs about four minutes a week.

There is a second argument for it that has nothing to do with appearance. Ludewig and Reynolds describe how scapular kinematics relate to shoulder pathology, and the muscles that control the shoulder blade and the back of the shoulder are the ones most likely to be undertrained in someone who presses frequently. Kolber and colleagues, reviewing shoulder injuries attributed to resistance training, point in the same direction. Work behind the shoulder is not decoration.

Setting up and executing

Take a dumbbell in each hand and stand with your feet about hip width. Push the hips back and hinge forward until the torso is close to parallel with the floor. Keep the spine long rather than rounded, and let the knees bend slightly so the hamstrings are not the limiting factor.

Let the dumbbells hang straight down under the shoulders. Set a soft bend at the elbow and then leave it alone for the rest of the set. Palms face each other.

Raise both arms out to the sides in a wide arc, leading with the elbows so the elbow stays slightly higher than the hand. Stop when the upper arms are roughly level with the torso. Going higher does not add rear delt work, it just adds trap work.

Pause for a beat at the top. You are looking for a contraction behind the shoulder, not a squeeze between the shoulder blades. If everything you feel is between the shoulder blades, the arms are travelling backwards rather than sideways.

Lower over about two seconds and stop just short of the bottom so the tension never fully releases. Then repeat.

The mistakes that cost you the most

Nearly every fault on this exercise comes from one of two decisions: not hinging far enough, or picking a weight that suits your pride rather than your rear delt.

Standing too upright is the more subtle of the two. Gravity always pulls straight down, so the resistance profile of a dumbbell depends entirely on your torso angle. At forty five degrees, a large part of the load is trying to pull your arms forward rather than down, and the rear delt only fights the component that matters. Get close to parallel and the geometry works for you.

Too much weight produces the rest of the list at once. The torso starts heaving upwards to launch the dumbbells. The elbows bend to shorten the lever. The shoulders shrug. The lowering half gets dropped. Every one of those is the body finding a way around a load it cannot handle in the intended path.

The lowering half deserves its own mention because it is the half most people give away. Schoenfeld and colleagues found a small hypertrophy advantage for eccentric-emphasised training in their meta-analysis, and Roig and colleagues reported a similar direction of effect for strength and mass. The effect is modest, but on an exercise where the total tension is already small, giving away half the rep is not a rounding error.

Sets, reps and rest by goal

This is a high rep exercise regardless of what you are training for. The rear delt is small, the leverage is poor, and heavy loading simply moves the work somewhere else.

For muscle gain, three to four sets of twelve to twenty with about a minute of rest. For strength work, three sets of ten to fifteen with ninety seconds, though strength on a reverse fly is mostly a proxy for control rather than a goal in its own right. In a fat loss phase, three to four sets of fifteen to twenty five with shorter rests keeps the density up without needing heavy dumbbells.

Schoenfeld and colleagues found a dose response between weekly set volume and hypertrophy, which is the argument for treating this as something you do two or three times a week in small doses rather than once a week in a large one. Refalo and colleagues found that sets taken close to failure drive hypertrophy well without needing to hit absolute failure every time, which suits an exercise where the last grinding rep usually turns into a heave.

Where it fits in your split

The reverse fly is an accessory. It goes after the compound work, never before it.

On a push, pull and legs split it fits either on push day beside lateral raises, or on pull day beside face pulls. Both are defensible. If your pressing volume is high, put it on push day so it lands on the same session that created the imbalance.

On an upper and lower split it belongs in the upper accessory block. On a bro split it lands late on shoulder day. On a full body programme it is the first thing to cut when time is short, and the first thing to add back when it is not.

Two or three exposures a week of two or three sets each will do more than one session of six sets, and it costs almost nothing in recovery.

Variations worth knowing

The cable version is the most useful upgrade. Standing between two low or chest height pulleys with the cables crossed gives you tension at the bottom of the arc, exactly where the dumbbell gives you none. The rear delt is stretched there, and that is not a part of the range you want unloaded.

Chest-supported versions, either on an incline bench or in a reverse pec deck machine, remove the hinge. That means no lower back fatigue and no possibility of swinging, which makes them the easiest versions to take genuinely close to failure. If you find that your reverse fly sets end because your back is tired rather than your shoulders, switch.

Band pull-aparts are the home option and a good warm-up before pressing. Face pulls are the closest relative worth rotating with, since they add external rotation to the same transverse pull.

What the evidence says

Coratella and colleagues measured lateral and frontal raise variations in competitive bodybuilders and found that the deltoid portions respond differently depending on the variation used. The general lesson transfers: small changes in arm path change which part of the deltoid does the work, which is why the difference between taking the arms out and taking them back is not pedantry.

Vigotsky and colleagues have written the standard caution about reading too much into surface electromyography amplitudes. A higher signal in one exercise does not prove more growth. Treat the electromyography literature as a guide to which movements plausibly reach the rear delt, not as a ranking table.

What is well supported is more mundane. Volume drives growth within a reasonable range. Sets close to failure work. Controlled lowering is worth keeping. Apply those three things to a movement that actually reaches the back of the shoulder and you have covered almost everything that matters here.

Common questions

How much weight should I use on reverse flies?

Less than you think. The test is simple: if you cannot pause for a beat at the top of the rep without the torso rising or the elbows folding, the dumbbells are too heavy. Most people are well served by something in the five to ten kilogram range even after years of training, and there is no prize for more.

Should I feel this between my shoulder blades?

Not mainly. A squeeze between the shoulder blades means the rhomboids and mid traps are doing the work, which usually means your arms are travelling backwards rather than out to the sides. You want the sensation behind the shoulder joint itself. Widen the arc and check your torso angle.

Is the reverse fly better than the face pull?

They are complements rather than competitors. The reverse fly is pure transverse abduction. The face pull adds external rotation and more scapular retraction. If you only have room for one, the face pull covers slightly more ground. If you have room for both, run them on different days.

How often should I train rear delts?

Two or three times a week works well. The muscle is small, the loads are light, and recovery cost is minimal, so frequent small doses beat one heavy session. Spreading the same weekly set total across more sessions also keeps the execution quality higher, because you are never grinding out set five with a load you cannot control.

Can I do reverse flies if my shoulder hurts when pressing?

Often yes, and it is one of the movements most likely to be tolerated. Pressing pain frequently comes from loaded overhead flexion, which this exercise avoids entirely. Keep the range at or below torso height and stay light. If the movement itself hurts, stop and get the shoulder looked at rather than working around it.