Rear Delt Fly
The rear delt fly is an isolation exercise for the back of your shoulders. You sweep your arms out and back in a wide arc, either sitting facing the pad of a fly machine or bent over with a pair of dumbbells. The rear deltoid does most of the work, and your middle traps and rhomboids help at the end of the rep. It is for anyone whose shoulders look strong from the front and flat from the side or back.
Rows and pulldowns hit the rear delts too, but your lats and biceps share the load, so the small rear delt rarely gets pushed to its limit. A fly removes those helpers because the elbow angle stays fixed and all the motion happens at the shoulder. That makes it a good balance for all the pressing in a typical program. The machine gives you a stable, repeatable setup, while dumbbells only need a little floor space.
Muscles worked
- Rear deltoid (primary)
Equipment
Dumbbells
How to do it
- Set the handles to the rear position and adjust the seat so the handles line up with your shoulders. Pick a load you could move for at least 15 reps.
- Sit facing the pad with your chest against it and your feet flat. Take the handles with your palms facing in or down, whichever feels steadier.
- Bend your elbows slightly and lock that angle in. Let your shoulders drift forward a little so you start with your rear delts lengthened.
- Sweep your arms out and back in a wide half circle, leading with your elbows rather than your hands. Stop when your upper arms are about in line with your shoulders or just behind.
- Pause for a second at the back without shrugging. Your chest stays on the pad the whole time.
- Return slowly along the same arc and stop just before the plates touch, so the tension stays on your rear delts.
Common mistakes
- Going too heavy. The rear delt is a small muscle, and a heavy load forces your traps and lower back to take over. Choose a weight you can pause with at the end of every rep.
- Turning the fly into a row. If your elbows bend as you pull, your arms and lats start helping. Keep the same slight bend from the first inch to the last.
- Squeezing your shoulder blades hard together. A big squeeze moves the work to your mid back. Think about your arms traveling wide, as if reaching for the walls on each side of you.
- Letting your shoulders ride up. A shrug brings in your upper traps. Keep your neck long and your shoulders low before each rep begins.
Variations
- Bent-over dumbbell rear delt fly : Use it when you have no machine. Hinge until your torso is close to parallel with the floor, let the dumbbells hang under your shoulders, then raise them out to the sides with soft elbows.
- Chest-supported dumbbell rear delt fly : Lie face down on an incline bench when bent-over reps start to swing or your lower back gets tired before your shoulders.
- Cable rear delt fly : Pick it for steadier tension at the start of the rep, where dumbbells feel almost weightless.
Sets and reps to start with
This is an accessory lift, so keep the reps high: 3 to 4 sets of 12 to 20 with 60 seconds of rest, stopping one or two reps short of failure. Beginners can start with 2 to 3 sets of 15 at a load that feels too easy for the first few reps. You can train rear delts two or three times a week since a few sets are easy to recover from, and they fit well at the end of a pull or shoulder session. Progress by adding reps first. Jumps in weight on a stack or a pair of dumbbells are large for this muscle, so only move up when you reach the top of your range with a clean pause.
Frequently asked questions
What does the rear delt fly work?
It works the rear deltoid, the back portion of your shoulder. Your middle traps and rhomboids help, especially near the end of the rep. Keeping your arms wide and avoiding a hard shoulder blade squeeze keeps more of the effort on the rear delt.
How heavy should rear delt flys be?
Light enough that you can do at least 12 reps with a pause at the back. Most people use far less than they would on a row, and that is normal for such a small muscle. If you need to swing or bend your elbows to finish a rep, the weight is too high.
Are rear delt flys better on a machine or with dumbbells?
Both work, and the machine is usually easier to learn. It holds your torso still and keeps tension on the muscle through the full arc, so it is hard to cheat. Dumbbells need more control and get harder toward the top, but you can do them anywhere.
Why do I feel rear delt flys in my traps?
Your traps usually take over when the load is too heavy or when you shrug and pinch your shoulder blades. Lower the weight, keep your shoulders down and focus on moving your arms out wide. Some trap involvement is normal, but your rear delts should be the first thing to burn.
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