Rear Delt Fly (Reverse Pec Deck)
The reverse pec deck fly is a machine exercise targeting the posterior deltoid. By reversing the pec deck movement, it isolates the rear shoulder and upper back retractors, improving posture and building balanced shoulder development.
How to do it
- Sit facing the pec deck machine and adjust the seat so your arms are parallel to the floor.
- Grip the handles with a neutral grip and keep a slight bend in your elbows.
- Pull the handles outward and backward in a wide arcing motion by squeezing your rear delts and shoulder blades together.
- Pause at the peak of the contraction.
- Slowly return the handles to the starting position and repeat for the desired number of repetitions.
Form cues
- Keep a soft, slightly bent elbow throughout the movement.
- Lead the motion with your elbows, not your hands.
- Squeeze your shoulder blades together at the back.
- Control the weight on the way back to the start.
Breathing: Exhale as you push the handles back and squeeze, and inhale as you slowly return to the starting position.
Common mistakes
- Using too much weight, which causes you to use momentum rather than your rear delts.
- Straightening your arms out completely, which puts unnecessary stress on your elbow joints.
- Shrugging your shoulders up toward your ears, which shifts the work to your traps instead of your rear shoulders.
Muscles worked
Primary: delts. Secondary: rhomboids, traps.
Suggested sets & reps
Get fitter
3 sets × 10–12 reps, rest 60 s
Lose weight
3 sets × 12–15 reps, rest 45–60 s
Build muscle
3–4 sets × 8–12 reps, rest 90 s
Easier, harder & alternatives
Make it easier
Make it harder
Take care if…
- If you feel sharp shoulder discomfort, ease off and choose a gentler option.
General educational guidance, not medical advice. Stop on sharp pain and check with a qualified professional if unsure.
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Start free →Frequently asked questions
Why do I feel this in my upper back instead of my shoulders?
The rear delts work closely with your upper back muscles like the rhomboids and traps, so feeling it there is completely normal. Focusing on leading with your elbows can help target the rear shoulders more directly.
How heavy should the weight be?
Start light. This is a small muscle group, so high weight is rarely necessary and usually just leads to poor form.
Can I do this exercise without a machine?
Yes, you can use dumbbells or resistance bands as effective alternatives.