Let’s talk about the most ignored, underrated, and criminally neglected muscle group in fitness: your rear delts. You know, those little muscles on the back of your shoulders that look like angel wings when they’re toned—and like deflated balloons when they’re not. If your shoulder routine is all front raises and lateral raises, you’re building a McMansion with no backyard. Enter the rear delt fly, the ultimate exercise for balancing your shoulders, fixing your posture, and finally filling out those tank tops.
As a trainer who’s rehabbed more rounded shoulders than I can count (thanks, desk jobs!), I’m breaking down exactly how to master this move. Spoiler: If you’re doing it wrong, you’re just waving your arms around. Let’s fix that.
What Is a Rear Delt Fly?
The rear delt fly is a shoulder exercise that primarily targets the posterior deltoids, which are the muscles on the back of your shoulders. It’s a simple yet effective movement, and when done correctly, it will transform your shoulder strength, posture, and even reduce the risk of injury.
Why Your Rear Delts Deserve Attention (And Why You’re Probably Ignoring Them)
Your rear delts aren’t just for looking good shirtless. They’re the glue that holds your shoulder health together. Weak rear delts lead to:
- Hunched posture (aka” Office Worker Syndrome”)
- Shoulder impingement (pain when reaching overhead)
- Imbalanced aesthetics (big front delts + sad rear delts = chicken wing vibes)
The rear delt fly targets these muscles like a laser, pulling your shoulders back and down. Think of it as a posture corrector you can do in your living room.
Rear Delt Fly Muscle Worked
🎯 Primary Muscle Worked
🔄 Secondary Muscles Involved
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Rhomboids (major and minor) – Help retract the scapula (pull your shoulder blades together).
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Trapezius (middle and lower fibers) – Assist in stabilizing and moving the shoulder blades.
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Infraspinatus & Teres Minor (Rotator cuff muscles) – Help with external rotation and shoulder stability.
How to Do the Rear Delt Fly Properly
Form is everything when it comes to the rear delt fly. Without proper form, you won’t be targeting the correct muscles, and you might even risk injury. Here’s how to do it right:
1. Seated Rear Delt Fly (Using Dumbbells or Machine)
Step 1: Sit on a bench or machine with your feet flat on the ground. Lean slightly forward from your hips to keep your back straight and abs engaged.
Step 2: Hold a dumbbell in each hand with your palms facing each other. Your elbows should be slightly bent to maintain tension throughout the movement.
Step 3: Raise the dumbbells out to the side, keeping your arms at about shoulder height. Focus on squeezing your shoulder blades together at the top of the movement.
Step 4: Slowly lower the weights back down, controlling the motion to avoid using momentum.
Tip: Keep your neck relaxed and avoid shrugging your shoulders up during the movement.
2. Bent-Over Rear Delt Fly (Dumbbells)
Step 1: Stand with your feet shoulder-width apart, holding a dumbbell in each hand.
Step 2: Hinge at your hips, keeping a slight bend in your knees and your back flat. Let the dumbbells hang down in front of you with a neutral grip (palms facing each other).
Step 3: While keeping a soft bend in your elbows, raise both dumbbells out to the sides, focusing on pulling your elbows back rather than just your hands. Think about trying to “pinch” your shoulder blades together.
Step 4: Slowly lower the dumbbells back to the starting position.
Step 5: Repeat for your desired reps.
Tip: Maintain a strong core throughout to protect your lower back and avoid arching.
3. Reverse Pec Deck Machine
Step 1: Adjust the machine’s seat so that your arms are aligned with your shoulders when sitting down.
Step 2: Hold the handles with your arms extended in front of you, palms facing down.
Step 3: Keeping your chest firmly pressed against the pad, pull the handles back and out to the sides, focusing on squeezing your shoulder blades together.
Step 4: Control the weights as you slowly bring the handles back to the starting position.
Step 5: Repeat for the desired reps.
Tip: Keep a controlled tempo to maximize tension on the muscles.
Rear Delt Fly Variations to Spice Up Your Workout
If you’re feeling like your rear delt fly routine is getting stale, try switching things up with these variations:
1. Single-Arm Rear Delt Fly
Perform the rear delt fly one arm at a time, which allows you to focus on each side individually. This is a great option if you’re dealing with any imbalances between your left and right shoulders.
2. Banded Rear Delt Fly
Attach a resistance band to a sturdy object and perform the rear delt fly, mimicking the movement you’d do with dumbbells. The band will provide constant tension and activate the muscles differently than dumbbells or cables.
3. Cable Rear Delt Fly
Set the cable machine to a low setting and use the ropes or handles to pull outward in the same motion as a dumbbell rear delt fly. Cables provide constant resistance and offer a different feel compared to free weights.
4. Rear Delt Fly with Reverse Grip
Holding the dumbbells with an underhand (supinated) grip during your rear delt fly can target the upper back and posterior delts in a slightly different way.
The 3 Deadly Sins of Rear Delt Flies (And How to Fix Them)
Sin: Using momentum like you’re auditioning for Riverdance.
Fix: Lighten the weight. If you can’t pause at the top, it’s too heavy.
Sin: Letting your elbows flare out.
Fix: Keep elbows slightly bent and pointed backward, not sideways.
Sin: Rounding your upper back like a scared cat.
Fix: Chest up, core braced, spine neutral.
“But I Don’t Feel It in My Rear Delts!”
Common complaints (and solutions):
“I feel it in my traps/upper back.”
→ Lower the weight. Focus on squeezing ONLY the rear delts.
“My lower back hurts.”
→ Reduce the hinge angle. Sit on a bench and lean forward instead.
“It’s too easy.”
→ Add a 2-second pause at the top. Or try drop sets.
How to Program Rear Delt Flys Into Your Routine
For Hypertrophy (Growth):
- 3-4 sets of 12-15 reps
- Rest 60 seconds between sets
- Pair with face pulls or rows
For Strength/Endurance:
- 4-5 sets of 8-10 reps (heavier weight)
- Rest 90 seconds
- Pair with pull-ups or deadlifts
For Posture Correction:
- 2-3 sets of 15-20 reps (light weight)
- Do daily as a warm-up or finisher
FAQs
Is the rear delt fly for shoulders or back?
Primarily for the rear (posterior) delts, but it also activates the upper traps, rhomboids, and rotator cuff muscles in the upper back.
Should I use dumbbells or a machine?
Both work:
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Dumbbells: More freedom of movement and engages stabilizers.
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Machine (reverse pec deck): Provides better isolation and is easier to control, especially for beginners.
How often should I train rear delts?
Train them 1–3 times per week, depending on your routine. They’re often undertrained, so including them regularly can help prevent shoulder imbalances.
Can I do rear delt flys at home?
Rear delt fly vs. reverse fly – same thing?
Yes, they’re often used interchangeably. Both target the same muscle group, although “reverse fly” may refer more broadly to machine or cable versions.
The Bottom Line
Rear delt flies aren’t glamorous, but neither is hunching like Quasimodo. Whether you’re lifting 5 lbs or 50, nailing this move will transform your shoulders from “meh” to “damn.”
Your mission: Add rear delt flys to your next workout. No excuses.
