ExercisesStrength Training — Machines
Machine Rear Delt Fly: A Complete Guide
Also called Rear Delt Machine, Reverse Pec Deck
Quick Intro
Machine Rear Delt Fly, also called the Rear Delt Machine or Reverse Pec Deck, is a machine-based strength training exercise performed seated facing the chest pad, pulling padded arms outward and back against resistance. Running the pec deck pattern in reverse trades chest emphasis for a rear delt and upper back focus, using the same style of fixed, guided pivot points.
Equipment Needed
A rear delt fly machine is required, often a pec deck with the arms set to its reverse position. No other equipment is needed.
Why It Matters
This is a small-muscle exercise suited to accumulated volume, not a single heavy pull, and it builds endurance and strength in about equal measure. The back of the shoulder (deltoid, posterior) does most of the work, backed by the muscles between the shoulder blades (rhomboids) and the upper back muscle running across the shoulders (trapezius). Because the chest pad locks the torso in place before the first rep even starts, matching the seat height to the shoulders is the setup detail that decides which fibers end up doing the work.
When to Do It
Machine Rear Delt Fly works well as a beginner-friendly entry into rear delt training, or for anyone who wants the pattern without the balance demand a cable or free-weight version adds. It also suits a higher-frequency approach than most shoulder exercises, since the light, guided load is easy to recover from. Three or more short sessions a week is realistic for many people.
Anyone with a current shoulder issue should still get individual guidance before starting, since bracing the chest against a fixed pad doesn’t remove all load from the joint itself.
Getting Ready
Rolling the shoulders backward a few times settles the joint before sitting down at the machine. Running through one easy set to lock in the seat height and elbow-led pattern is worth doing every session, not just the first.
Step-by-Step Instructions
1. The setup. Sit facing the machine with the chest against the pad and the forearms or hands against the padded arms.
2. The starting position. Let the arms come together in front, feeling a light stretch across the upper back.
3. The pull. Lead with the elbows and pull the padded arms outward and back, squeezing the shoulder blades together.
4. The return. Bring the arms back together under control, resisting the machine’s pull the whole way.
How Many, How Often
Machine Rear Delt Fly is dosed by reps, sets and the weight on the stack, with the load chosen relative to how well the elbows lead the pull through a full set.
| Level | Where you’re at | What to do |
|---|---|---|
| Beginner | New to a machine reverse fly | 3 sets of 12 to 15 reps with a light weight, focused on leading with the elbows |
| Intermediate | The elbows stay high and lead the pull consistently | 3 sets of 10 to 12 reps with a weight where the last 1 to 2 reps are hard for the rear delts |
| Advanced | Comfortable working near a heavy top set | 3 to 4 sets of 8 to 12 reps, occasionally pausing at the widest point for extra tension |
Elbows leading the pull matters more here than how much weight sits on the stack, since pulling mostly with the hands brings the biceps in and takes work away from the rear delts.
Modifications and Variations
On a cable, Face Pull trades the seated reverse fly for a standing rope pull that adds an external rotation finish.
With free weights, Rear Delt Fly moves the same reverse fly pattern to free weights performed bent over or lying face down on an incline bench.
Common Mistakes to Avoid
Pulling mostly with the hands. Gripping hard and yanking the pads back with the hands shifts effort from the rear delts toward the forearms and biceps. Treating the hands as hooks and driving the movement from the elbows keeps the target muscles doing the work.
Ignoring the seat height. Sitting down and starting a set without checking where the handles line up relative to the shoulders is an easy way to spend a whole session training the wrong angle. A quick seat check before every session is worth the ten seconds it takes.
Cutting the range short as the weight goes up. Chasing a heavier pin setting until the arms only travel through part of the arc trades most of the exercise’s benefit for a bigger number. A lighter pin setting moved through the whole arc gets more out of each rep.
After Your Set
Rolling the shoulders forward and backward a few times settles the joint after a set of reverse fly work. A gentle cross-body stretch on each arm finishes loosening the back of the shoulders.
Going Deeper
Machine Rear Delt Fly is a good entry point for people who haven’t trained the rear delts directly before, since the seated, guided path removes nearly every technical variable except elbow position. Once the seat height and elbow-led pattern feel automatic, it’s easy to stop paying attention to either one, and a session’s worth of volume can land on the wrong muscles unnoticed. Rechecking the seat height and elbow position every few sessions gets past a plateau sooner than loading the stack.
Someone new to this exercise typically learns the correct seat height and elbow-led pattern within the first couple of sessions, then adds working weight steadily over four to six weeks as the rear delts adapt.
How to Know You’re Improving
- A pull that visibly starts from the elbows on each rep
- A seat height check that becomes an automatic habit before sitting down
- A brief hold at the widest point before releasing
- A pin setting that keeps climbing while the full arc stays intact
An automatic elbow-led pattern and a checked seat height matter more here than the pin setting alone.
Muscles Worked
- Posterior Deltoid (the back of the shoulder, leading the pull on the fixed arms)
- Rhomboids (the muscles between the shoulder blades, assisting the squeeze)
- Trapezius (the upper back muscle running across the shoulders, steadying the shoulder against the machine’s fixed backward arc)
FAQ
Is Machine Rear Delt Fly better than Face Pull? Neither is strictly better. This version guides the pull along a fixed, seated path, while Face Pull is a standing rope pull with a wrist rotation that works the rotator cuff, and many shoulder programs benefit from including both.
Why does seat height matter so much for this exercise? Setting the seat too high or too low changes the angle the arms travel through relative to the shoulders, which shifts how much of the work lands on the rear delts versus the surrounding muscles.
How does the dumbbell rear delt fly differ? Rear Delt Fly is performed with free weights, either bent over or lying face down on an incline bench, adding a balance and stabilization demand, while this version uses a fixed, guided path that removes most of that demand.
Is some upper back fatigue after this exercise normal? Yes, a burning, tired feeling settling into the rear delts and between the shoulder blades by the end of a set is normal. A sharp pain that lingers past the set, especially deep in the joint, is worth having a doctor or physical therapist check.
How often should the machine rear delt fly be trained? Two to three times a week works for most people, especially since the rear delts also get some indirect work from rowing movements earlier in a session.
Related to Face Pull and Rear Delt Fly as cable and free-weight alternatives.