Comparison · Rear Delts
Rear Delt Fly vs Reverse Pec Deck: Same Arc, Different Support
Both sweep the arms back to shoulder height, and both target the rear delts. What changes is who holds your torso, you or a pad, and that decides how hard each set can go.
The verdict
The Rear Delt Fly and the Reverse Pec Deck train the same rear delt arc, but the dumbbell fly makes you support your own torso and loads the top of the rep hardest, while the machine braces your chest and keeps resistance on through the whole sweep. Pick the Rear Delt Fly at home or with dumbbells only; pick the Reverse Pec Deck in a gym when you want sets taken close to failure.
Illustrations adapted from Everkinetic via workout-guide, CC BY-SA 4.0. Full credits.
At a glance
| Aspect | Rear Delt Fly | Reverse Pec Deck |
|---|---|---|
| Equipment | Dumbbell | Machine |
| Where | Home or gym | Gym |
| Level | Beginner | Beginner |
| Back zone it leads | Rear Delts | Rear Delts |
| Muscles | Rear Delts, Infraspinatus | Rear Delts, Rhomboids |
| Typical work | 3 × 12–15 | 3 × 12–15 |
| Torso support | You hold the hinge, or lie on a bench | Chest pad holds you; nothing to brace |
| Resistance curve | Light at the bottom, heaviest at the top | Loaded from the first inch to the finish |
| Path of the arms | Free; each arm finds its own arc | Fixed by the machine’s lever arms |
| Shoulder blades | Stay mostly still as the arm rotates out | Draw together at the finish |
| Weight jumps | Dumbbell steps, often large for a small muscle | Small pin increments on the stack |
| Going to failure | Form slips as the hinge tires | Easy to grind out the last reps |
| Second muscle | Infraspinatus, from the outward rotation | Rhomboids, from the blade squeeze |
What the Rear Delt Fly and Reverse Pec Deck have in common
Both are flys in the literal sense: the elbow keeps a slight, fixed bend while the upper arm travels from in front of the chest out to shoulder level. The rear delts do the sweeping in each, the library tags both as beginner movements in the Rear Delts zone with Upper Back as a secondary zone, and both default to three sets of 12 to 15. Neither needs much weight. The classic error is shared too: bending the elbows further as the set gets hard, which turns the sweep into a row and hands the load to bigger muscles.
The differences that matter
Who holds the torso. With dumbbells, you do. The standing version is a hinge held for the entire set, and your hamstrings and lower back often quit before the delts; seated or chest-down on a bench fixes that but takes setup. On the Reverse Pec Deck you sit with your chest pressed into the pad, so the back of the shoulder is the only thing working hard, and the set ends when the delts are spent.
Resistance through the arc. A dumbbell only pushes straight down. With the arms hanging it weighs almost nothing, and the load peaks as the arms come level with your torso. The machine’s arms swing on a pivot and pull against the stack from the very start, so the opening part of the rep counts too. Per set, you get more time under load on the machine.
Muscles beyond the delts. The free path of a dumbbell lets the upper arm rotate outward at the wide end, which recruits the infraspinatus. The machine’s fixed path limits that rotation but allows the shoulder blades to draw together at the finish, so the rhomboids join instead. Neither builds the mid-back on its own, yet the pec deck carries slightly more upper-back work.
Loading and progress. Stack plates move in small steps, and a machine set can go to the last possible rep without technique falling apart. Dumbbells jump in steps that are big for a small muscle, so progress on the fly usually comes from reps and a pause at the top before you reach for a heavier pair.
When to pick the Rear Delt Fly
Choose the Rear Delt Fly when a pair of dumbbells is all you have, or when the machine is always occupied. It works at home, in a hotel gym, or tacked onto any session with no setup. It is also the better pick if you want the infraspinatus trained alongside the rear delts, since the free path lets the arms rotate outward at the top. If your hinge gives out first, sit on a bench edge or lie chest-down on an incline; the stimulus stays the same and the delts become the limit.
When to pick the Reverse Pec Deck
Choose the Reverse Pec Deck when you train in a gym and want the hardest rear delt sets you can manage. With your chest on the pad there is no balance or hinge to manage, so you can go to failure, hold for a second where the arms line up with the shoulders, and run drop sets by moving the pin. It is also the quicker movement to learn: set the seat so the handles sit at shoulder height and let the machine steer. Lifters who struggle to feel their rear delts often find them here first.
How to do the Reverse Pec Deck →
Can you do both?
Running both makes sense, since each covers the other’s weak spot. Use the Reverse Pec Deck for the demanding work, 3 sets of 12 to 15 with the last set taken to failure, then finish with 2 sets of 15 to 20 Rear Delt Flys lying chest-down on an incline bench, light and slow. On a second weekly session, dumbbells alone are enough, because rear delts recover quickly. If you only have room for one, alternate by training block: four weeks on the machine, then four on dumbbells.
Frequently asked questions
Is the reverse pec deck better than the rear delt fly?
For pushing the rear delts hard, the machine usually wins, because the chest pad removes the hinge and the stack moves in small steps. The dumbbell Rear Delt Fly wins on convenience and works at home. Both hit the same muscle through the same arc, so the better one is whichever you can load consistently week after week.
Is the reverse fly machine the same as the reverse pec deck?
Yes. Reverse pec deck, rear delt machine and reverse fly machine are names for the same station: a pec deck used facing the pad, with the handles set behind you. Some gyms have a dedicated rear delt machine with its own seat and handles, but the movement is identical, with the arms sweeping back from in front of the chest until they line up with the shoulders.
Which is better for beginners, the rear delt fly or the reverse pec deck?
The Reverse Pec Deck is easier to learn, because the machine sets the path and holds your torso. The Rear Delt Fly asks a beginner to hold a hinge, keep the elbows soft and resist swinging, all at once. Both are rated beginner movements, though, and the fly gets much easier if you learn it chest-down on an incline bench before trying it standing.
How heavy should a rear delt fly be?
Light. Most people use dumbbells well under what they would row, because the long lever makes a small weight feel heavy at the top. Pick a pair that lets you reach shoulder height on all 12 to 15 reps without swinging, and pause briefly at the top of each. If the weight only moves with a jerk from the hips, go down a size.
Let your back decide
BackMaxx scores six back zones and eight muscles from one photo. If your rear delts is what is behind, it builds the week around it — and picks between movements like these for you.
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