Pec Deck Rear Delt Machine Fly: How To Do, Muscle Worked

The machine rear delt fly also known as reverse pec deck fly is a simple yet effective exercise that increases deltoid muscle definition and strength.

The pec deck rear delt machine fly targets your upper back muscles and shoulder muscles, particularly the rear deltoids, (backside of your shoulders), Traps and rhomboid.

A well-developed rear delt that is a very important feature for lifters and bodybuilders. It’s often considered one of the best things you can have.

If you are not familiar with the correct form, it can be difficult to perform this exercise. This is where the ultimate guide comes in.

In this post, we will discuss the following point:

  • What is the machine rear delt fly?
  • Benefits of it.
  • What muscles does the pec deck delt fly target?
  • How to perform it correctly?
  • Best Alternate of it.

What Is The Machine Pec Deck Rear Delt Fly?

The rear delt machine fly is an isolation exercise designed to train the rear delt, trap, and Rhomboids muscles. However, the term ‘isolation movement’ can be misleading. To clarify, it is more accurately described as a single-joint exercise in order to avoid confusion.

During the machine rear fly, the movement is felt primarily at the rear delt and upper back. Imagine spreading your arms wide as if you were giving someone a big hug, but in reverse, instead of pulling forward like a machine chest fly.

The rear delt pec deck fly offers several advantages over other rear delt fly.

  • Pec deck machine design ensures proper form and minimizes the involvement of other muscle groups, allowing for more targeted and effective rear deltoid activation.
  • The machine provides a consistent resistance throughout the movement, which ensures a balanced and controlled workout.

Pec Deck Rear Delt Machine Fly Muscle Worked

The rear delt machine flys primarily muscle worked Rear deltoid.

In addition to its target, the main rear delt muscles. The pec deck delt fly has the involvement of several other muscles, these muscles include,

Rear Delt Machine Fly Muscle Worked

Benefits Of Machine (Pec Deck) Rear Delt Fly

Pec Deck delt fly exercises also help to:

  • It specifically targets and strengthens the rear deltoid muscles, which help to develop a well-rounded shoulder.
  • Improve posture by reducing the effects of rounded shoulders.
  • Prevent shoulder injuries by boosting shoulder stability.
  • Build symmetry with the shoulder, preventing a “forward sloping” look
  • For a variety of sports and physical activities, strong rear deltoids are essential, as they contribute to movements such as pulling, rowing, and throwing motions.
  • The machine rear delt fly ensures a consistent and targeted engagement of the rear deltoids, while minimizing the involvement of other muscle groups.
  • This is a fast way to work on the deltoids and doesn’t require much preparation.
  • The machine’s setup and adjustability are user-friendly, allowing for a hassle-free workout experience.
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How To Do Pec Deck Rear Delt Machine Fly

The Rear delt fly machine provides consistent resistance throughout the entire range of motion. Additionally, this machine offers various technical adjustments, such as grip positions, trajectory, and range of motion settings.

These adjustments can help isolate and target the posterior deltoid muscles effectively.

Pec Deck Rear Delt Machine Fly

Here’s a step-by-step guide on how to do it:

  1. The seat height and position of the handles should be adjusted to ensure a comfortable fit for your body size.
  2. Sit on the machine with your chest against the pad or support. Your feet should be flat on the floor, and your knees should be slightly bent. Grab the handles.
  3. Maintain a tall, upright posture throughout the exercise. Keep your shoulders relaxed and avoid shrugging them up.
  4. Maintaining a slight bend in your elbows and pull your arms outward and backward in an arc-like motion, simultaneously.
  5. Keep pulling until your arms are stretched out to the sides.
  6. Hold the contracted position for a brief moment to emphasize the tension in your rear deltoids.
  7. Slowly release the tension and return your arms to their starting position.
  8. Repeat for the desired number of reps.

Tips And Form For Rear Delt Pec Deck Machine Fly

  • Keep a controlled motion and avoid jerky movements.
  • Start with lighter weights to focus on technique and form.
  • Throughout the exercise, keep your elbows slightly bent. Avoid fully extending or locking out your elbows.
  • Focus on squeezing your shoulder blades together at the peak of the movement to activate your rear deltoid muscles.
  • Perform the exercise in a slow and controlled manner, emphasizing the eccentric (lowering) phase.
  • Exhale as you pull your arms back, and inhale as you come back. During the exercise, keep your breathing steady.
  • You should aim to complete 3-4 sets of 10-12 reps of the machine rear delt fly.
  • Perform the exercise 2-3 times a week for optimal results.
  • Pair it with other shoulder exercises that target different parts of the shoulder for a well-rounded workout.
  • As you become more comfortable with the form, feel free to change your set and rep ranges to challenge yourself.

Different Grip Position Of Pec Deck Machine Rear Delt Fly

The use of different grip positions during the machine rear deltoid fly can provide unique benefits and target the rear deltoid muscles from slightly different angles.

Pronated Grip (Overhand Grip)

In this grip position, your palms are facing downward.

  • Wider Activation: The pronating grip emphasizes the posterior deltoids and helps to engage the outer portions of the rear delts.
  • Increased Shoulder External Rotation: The pronating grip encourages greater shoulder external rotation, which can improve mobility and flexibility in the shoulder joint.
Pronated Grip Machine Rear delt fly

Hammer Grip (Neutral Grip)

The hammer grip refers to a grip position where your palms are facing each other, similar to holding a hammer.

  • Balanced Muscle Activation: The neutral grip distributes the workload more evenly between the rear deltoids and the middle delts.
  • Reduced Stress on the Wrists: It places the wrists in a more neutral position, reducing the strain on the joint compared to other grip positions.
Hammer Grip Pec Deck Rear Delt Machine Fly

Supinated Grip (Underhand Grip)

In a supinated grip, your palms are facing upward.

  • Heightened Rear Delt Focus: It places greater emphasis on the rear deltoids, helping to isolate and target them more effectively.
  • Enhanced Bicep Engagement: The supinated grip also recruits the biceps to a greater extent.
Different Grip Position Of Pec Deck Machine Rear Delt Fly
Know More: 25 Best Rear Delt Exercises For Mass And Strength

Reps, Sets, And Frequency For Rear Delt Machine Fly


  • Reps: Start with 8-10 repetitions per set.
  • Sets: Perform 2-3 sets of the exercise.
  • Frequency: Include the exercise in your shoulder workout routine 1-2 times per week.


  • Reps: Aim 10-15 repetitions per set.
  • Sets: Aim for 3-4 sets of the exercise.
  • Frequency: 2-3 times per week.


  • Reps: Increase the challenge by performing 12-15+ repetitions per set.
  • Sets: Perform 4-5 sets of the exercise.
  • Frequency: 2-3 times per week.

Best Variations Of Pec Deck Rear Delt Fly

1. Single-Arm Pec Deck Rear Delt Fly

Instead of using both arms simultaneously, perform the exercise one arm at a time.

This variation helps to address any strength imbalances between the two sides and improves focus and isolation of the rear deltoid muscles.

2. Alternating peck deck rear delt fly

The Alternating machine rear delt fly is an exercise variation in which you perform the movement with one arm at a time in alternating fashion.

You should sit on the machine, grab the handles with an overhand grip, retract your shoulder blade, and pull your one arm outward and backward.

Hold the contraction for a few seconds before returning to the starting position. Alternate arms and repeat for the desired number of repetitions.

Best Alternates Of Pec Deck Rear Delt Fly

If you’re looking for a similar exercise to replace the pec deck machine rear delt fly during your training sessions, you can try these alternatives.

Rear Delt Machine Fly vs Rear Delt Dumbbell Fly

Rear Delt Fly Machine:

  • The machine provides focused isolation and engagement for the rear deltoid muscles.
  • It provides a consistent resistance throughout the movement.
  • The pec deck machine provides stability and support, which reduces the risk of improper form or injury.
  • Machines are generally easy to use, which makes them suitable for beginners or those who may struggle with coordination or balance during free weight exercises.

Dumbbell Rear Delt Fly

  • The dumbbell rear fly allows for a wider range of motion, providing a deeper stretch and contraction of the rear deltoids.
  • It requires more stabilizing muscles, which leads to increased muscle activation and development.
  • Using dumbbells is hard because you have to keep the correct posture while doing this exercise.
  • Dumbbells are easy to find and can be used at home or in the gym. This means you can do dumbbell rear fly exercise whenever you want.


Is the rear delt fly machine effective?

Yes, the rear delt fly machine can be an effective exercise for targeting and strengthening the rear deltoid muscles. It provides a consistent resistance throughout the range of motion, and offers various grip adjustment options.

How much weight should I lift on the rear del pec deck fly?

You should always choose your weight based on how experienced you are, no matter what exercise you are doing. Lifting too heavy can make your form worse and increase your risk of getting hurt.

Is the reverse pec deck for back or shoulders? 

The reverse pec deck is beneficial for both your back and shoulders. The reverse pec deck targets the upper back, and shoulder muscles, specifically the traps, deltoid, and rhomboids. 


Don’t overlook the significance of working out your rear deltoids as part of your workout regimen.

The pec deck machine rear delt fly is a great exercise for anyone who wants to shape their shoulders and improve their posture and shoulder mobility.

When you consistently challenge and engage your rear deltoids, you will notice improvements in shoulder strength.


  • Campos YAC, Vianna JM, Guimarães MP, Oliveira JLD, Hernández-Mosqueira C, da Silva SF, Marchetti PH. Different Shoulder Exercises Affect the Activation of Deltoid Portions in Resistance-Trained Individuals. J Hum Kinet. 2020 Oct 31;75:5-14. doi: 10.2478/hukin-2020-0033. PMID: 33312291; PMCID: PMC7706677.
  • Schoenfeld B, Sonmez RG, Kolber MJ, Contreras B, Harris R, Ozen S. Effect of hand position on EMG activity of the posterior shoulder musculature during a horizontal abduction exercise. J Strength Cond Res. 2013 Oct;27(10):2644-9. doi: 10.1519/JSC.0b013e318281e1e9. PMID: 23302754.

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