If you’re searching for “how to do rear delt fly” or exploring “rear delt fly exercises,” you’re on the right track to building balanced, powerful shoulders. The rear delt fly — whether using dumbbells, cables, or a machine — is a key isolation exercise that targets the often-neglected posterior deltoids (rear delts). It’s ideal for improving posture, enhancing upper body shape, and boosting performance in compound lifts like bench presses and rows. In this guide, we’ll show you correct form, share the main benefits, and suggest a great alternative exercise.

What Does the Rear Delt Fly Work?

The rear delt fly mainly targets the posterior deltoids — the muscles at the back of your shoulders that help pull your arms back and outwards. Supporting muscles include the rhomboids, traps, and lower back, which work together to stabilise your body and improve overall balance. Strengthening these areas helps correct posture and ease tension caused by sitting or hunching forward for long periods.

Key Benefits of Rear Delt Fly Exercises

• Stronger, More Stable Shoulders: Builds shoulder resilience, helping you lift heavier weights more safely and efficiently.
• Better Posture: Strengthens the upper back muscles to counteract rounding of the shoulders.
• Improved Shape and Symmetry: Creates the “3D shoulder” look, balancing out your front and middle delts for a more athletic physique.
• Injury Prevention and Performance: Reduces the risk of shoulder strain and supports your movement in presses, rows, and deadlifts.

Aim for 3 to 4 sets of 10 to 15 reps, two to three times a week, to feel the difference without overtraining.

How to Do a Rear Delt Fly: Step-by-Step

Form is everything for this move. Keep your core tight, spine neutral, and control your tempo — no swinging or jerking. Start light and focus on muscle engagement over weight used.

Dumbbell Rear Delt Fly (Seated)

1. Sit on the end of a bench holding a dumbbell in each hand, palms facing in.
2. Lean forward slightly from the hips with a straight back and chest up.
3. Let your arms hang below you with a soft bend in your elbows.
4. Lift the dumbbells out to the sides until your elbows are level with your shoulders.
5. Squeeze your shoulder blades together, pause, then lower slowly.

Tip: Focus on slow, controlled movement — about two seconds up and three seconds down.

Standing Dumbbell Rear Delt Fly

1. Stand shoulder-width apart and hinge forward at the hips until your torso is almost parallel to the floor.
2. Hold dumbbells with palms facing in and elbows slightly bent.
3. Lift both arms outwards to shoulder height, keeping your core tight.
4. Control the descent back to the start position.

This standing version also works your core and hamstrings for extra stability.

Machine and Cable Rear Delt Fly

Machines and cables help maintain constant tension and are great for beginners learning range of motion.

Cable Rear Delt Fly

1. Set two cables to chest height and attach D-handles.
2. Cross the cables so each hand holds the opposite side.
3. Hinge forward slightly, keeping your back straight and knees soft.
4. Pull the cables outwards and back in a controlled arc, squeezing your rear delts at the end.
5. Return to start slowly.

Rear Delt Fly Machine (Reverse Pec Deck)

1. Sit facing the pad with your chest against it and feet flat.
2. Grip the handles slightly below shoulder height.
3. Pull the handles back and out, leading with your elbows until your arms are parallel to the floor.
4. Pause briefly and return slowly to the start position.

Tip: Adjust the seat height so your elbows stay level with your shoulders and focus on squeezing your rear delts, not your traps.

Rear Delt Fly Alternative: Face Pulls

Face pulls are a brilliant alternative that also strengthen the rotator cuff and improve posture.

1. Attach a rope handle to a cable machine set at chest height.
2. Stand tall, grip both ends of the rope with palms facing in.
3. Pull the rope towards your face, leading with your elbows, until your hands are in line with your eyes.
4. Squeeze your shoulders together, then slowly release back to the start position.

Do 3 sets of 12 to 15 controlled reps.

Common Mistakes and Pro Tips

• Arching your back: Keep a neutral spine to avoid strain.
• Using momentum: Lift with muscle control, not speed.
• Locking elbows: Maintain a soft bend to protect your joints.

Pro Tip: Warm up with band pull-aparts or light cable work to activate your shoulders before starting.

Wrap-Up: Build Strong, Balanced Shoulders

Mastering rear delt fly variations can transform your shoulder strength and posture. Start with dumbbells for control, then try cable or machine options for progressive overload. Mix in face pulls for balance and joint health. Consistency, control, and good form are what deliver the best results — your future self will thank you.

At Study Active, we’re here to help you understand the science behind effective training. Through our CIMSPA-endorsed, tutor-supported qualifications, you can learn how to programme exercises like these for clients — or enhance your own workouts with expert knowledge. Explore our personal training and fitness courses and take the next step in your career today.