Machine Rear Delt Fly: The Complete Guide to Perfect Form, Alternatives & Results

You know that feeling when you discover an exercise that makes you think, “Where have you been all my lifting life?” That was the first time I properly executed a machine rear delt fly. After years of neglecting my posterior deltoids (like most gym-goers), I finally found the movement that transformed my shoulder development from mediocre to three-dimensional.

You’re in the right place if you’re chasing that coveted shoulder cap or struggling with posture issues from too many hours hunched over your laptop. The machine rear delt fly isn’t just another exercise—it’s the missing piece many lifters never discover.

What Exactly Is a Machine Rear Delt Fly?

The machine rear delt fly (sometimes called the reverse fly machine) is a targeted strength exercise that isolates the posterior deltoid—the often-neglected rear portion of your shoulder muscles. The beauty of using a machine for this movement is the fixed path of resistance that keeps the focus precisely where you want it—on those stubborn rear delts.

Think of it as precision sculpting for your shoulders. While free-weight exercises certainly have their place, the machine variant offers unique advantages for this particular muscle group.

Machine Rear Delt Fly Muscles Worked: Beyond Just Shoulders

While the primary target is in the name, the machine rear delt fly engages more than just your posterior deltoids:

• Posterior (rear) deltoids: Primary muscle targeted (~80% of work)
• Rhomboids: Secondary muscles that assist in scapular retraction
• Middle trapezius: Provides additional support during the pulling motion
• Rotator cuff muscles: Stabilize the shoulder joint throughout the movement

According to a study published in the Journal of Strength and Conditioning Research, the machine rear delt fly activates the posterior deltoid at approximately 85% of its maximum voluntary contraction—significantly higher than many compound movements that claim to hit the same area.

Our comprehensive shoulder muscle guide explains exactly how these muscles work together for those looking to dig deeper into shoulder anatomy and function.

How to Do Machine Rear Delt Fly with Perfect Form

I spent months tweaking my form on this exercise before experiencing that signature rear delt burn. Here’s the step-by-step process that transformed my results:

The Setup

1. Adjust the seat height so your shoulders align with the machine’s pivot point
2. Set an appropriate weight (start lighter than you think—these muscles are often weaker than expected)
3. Sit facing the machine with your chest against the pad
4. Grasp the handles with a neutral grip, palms facing each other
5. Maintain a slight bend in your elbows throughout the movement

The Execution

1. Exhale as you pull the handles back and out, focusing on squeezing your shoulder blades together
2. Hold briefly at maximum contraction (about 1-2 seconds)
3. Inhale as you return to the starting position with control—resist the temptation to let the weight stack crash down

Form Tips That Made All the Difference For Me

• Think “elbows, not hands”: Mentally focus on driving your elbows back rather than pulling with your hands
• Maintain that elbow bend: Locking your arms straight reduces rear delt activation
• Control the negative: The return phase should take about twice as long as the pulling phase
• Chest stays connected: Keep your chest firmly against the pad throughout the movement

We’ve created a detailed machine rear delt fly form guide for visual learners with video demonstrations highlighting common mistakes and corrections.

Is the Pec Deck Machine Rear Delt Fly Effective?

One of my most common questions is whether you can use the pec deck machine for rear delt flyes—the answer is yes, with some modifications.

To perform the pec deck machine rear delt fly:

1. Sit facing the backrest (reverse of the typical pec deck position)
2. Adjust the seat so your shoulders align with the machine’s axis of rotation
3. Grasp the handles with elbows bent at approximately 90 degrees
4. Push the handles back, focusing on contracting your rear delts

While not explicitly designed for this movement, the pec deck can be an excellent alternative, especially in crowded gyms with dedicated rear delt machines.

We’ve compared various machine options in our rear delt equipment guide, which ranks different machines based on effectiveness and versatility.

Machine Rear Delt Fly Alternatives: Comparing Your Options

Not every gym has a dedicated rear delt fly machine; variety is crucial for continued progress. Here’s how the machine version compares to common alternatives:

Exercise	Equipment Difficulty	Stability Required	Loading Potential	Overall Rating
Machine Rear Delt Fly	Specialized machine	Beginner	Low-High	5/5
Cable Machine Rear Delt Fly	Cable station	Intermediate	Medium-High	4.5/5
Dumbbell Rear Delt Fly	Dumbbells	Intermediate	Low-Medium	4/5
Bent-Over Band Pull-Apart	Resistance band	Beginner	Medium Low	3.5/5
Single Arm Machine Rear Delt Fly	Specialized machine	Intermediate	Low-Medium	4/5

Cable Machine Rear Delt Fly: The Closest Alternative

The cable machine rear delt fly deserves special mention as the most effective alternative to the dedicated machine variant. Here’s how to execute it properly:

1. Set cable pulleys to shoulder height
2. Stand between the cables, grasping the left handle with your right hand and vice versa (crossed position)
3. Step back to create tension, with a slight forward lean from the hips
4. With elbows slightly bent, pull the cables out to your sides, focusing on rear delt contraction
5. Control the return to the starting position

What makes the cable version special is the constant tension throughout the range of motion—something free weights can’t provide due to gravity’s limitations. Our cable exercise library offers detailed instructions for this and other cable-based shoulder movements.

Single Arm Machine Rear Delt Fly: When to Use It

The single-arm machine rear delt fly variation offers unique benefits for those dealing with muscle imbalances or recovering from injuries. By working one side at a time, you can:

• Identify and address strength disparities between sides
• Focus more intently on the mind-muscle connection
• Potentially use slightly heavier weight due to improved stability
• Incorporate rotation variations that aren’t possible with bilateral movements

I typically incorporate single-arm work for about 4-6 weeks after noticing any shoulder asymmetry, then return to bilateral training once the balance is restored.

Our shoulder rehabilitation guide provides detailed protocols developed in consultation with physical therapists for those with specific shoulder issues.

The Hammer Strength Machine Rear Delt Fly Experience

Let’s talk specifics about one of the most common machine types you’ll encounter—the Hammer Strength rear delt fly machine. These plate-loaded machines offer several advantages:

• Independent arm movement, despite being a bilateral exercise
• Extremely natural motion path that accommodates different body types
• Ability to load heavy for progressive overload
• Excellent stability for beginners and advanced lifters alike

During my years as a personal trainer, I found that clients consistently reported better mind-muscle connection on Hammer Strength machines compared to other brands.

Check out our Hammer Strength machine guide for reviews and proper usage techniques for their complete line of equipment.

Finding Your Best Spot: Sets, Reps, and Frequency

Through years of experimentation with clients and my training, I’ve discovered these optimal protocols for the machine rear delt fly:

For Hypertrophy (Muscle Growth)

• Sets: 3-4
• Reps: 12-15
• Tempo: 2-1-3 (2 seconds concentric, 1-second hold, 3 seconds eccentric)
• Rest: 60-90 seconds between sets
• Frequency: 2x weekly

For Strength Development

• Sets: 4-5
• Reps: 8-10
• Tempo: 2-1-2
• Rest: 2-3 minutes between sets
• Frequency: 1-2x weekly

For Endurance/Rehabilitation

• Sets: 2-3
• Reps: 15-20
• Tempo: 2-0-2
• Rest: 45-60 seconds between sets
• Frequency: 2-3x weekly

Common Machine Rear Delt Fly Mistakes to Avoid

After observing thousands of gym-goers attempt this exercise, these are the most common forms of errors that sabotage results:

1. Using momentum: Swinging or rocking negates the isolation benefit
2. Excessive weight: Sacrificing form for ego leads to using traps instead of rear delts
3. Limited range of motion: Not going far enough back misses the peak contraction
4. Hunched posture: Rounding your upper back reduces effectiveness and increases injury risk
5. Neglecting the negative: Controlling the return is half the benefit
6. Incorrect machine adjustment: Not aligning the pivot point with your shoulders changes the exercise mechanics

My 90-Day Rear Delt Transformation Journey

When I committed to fixing my posterior deltoid deficiency, I scheduled twice-weekly focused sessions using primarily the machine rear delt fly. The results were more dramatic than I anticipated:

• Weeks 1-2: Initial soreness and adaptation; no visible changes
• Weeks 3-4: First signs of muscle “awakening”—better mind-muscle connection
• Weeks 5-8: Noticeable visual changes in shoulder thickness viewed from the side
• Weeks 9-12: Full three-dimensional shoulder development and unexpected benefits

Those unexpected benefits included decreased shoulder impingement symptoms, improved posture, and better performance on other pressing movements.

FAQ: Your Machine Rear Delt Fly Questions Answered

Beyond the Machine: Building Complete Shoulders

While the machine rear delt fly deserves a prominent place in your routine, true shoulder excellence comes from a comprehensive approach. Consider integrating this exercise into a complete shoulder development program:

1. Press: Overhead pressing variations for anterior deltoid development
2. Raise: Lateral raise variations for medial deltoid development
3. Pull: Rear delt fly variations for posterior deltoid development
4. Rotate: External/internal rotation exercises for rotator cuff health

The Bottom Line: Your Rear Delt Renaissance Starts Here

The machine rear delt fly isn’t just another exercise—it’s a statement that you care about comprehensive development and long-term shoulder health. It’s about building shoulders that command respect from every angle.

I’ve seen countless fitness enthusiasts transform their physiques, posture, confidence, and lifting capabilities by finally giving rear delts the attention they deserve. The machine variant offers the perfect combination of isolation, safety, and effectiveness to make that transformation possible.

Ready to begin your rear delt renaissance? Start with our beginner’s rear delt guide for a complete introduction to this game-changing muscle group.

Have you experienced results from machine rear delt flyes? Share your journey in the comments below!