Reverse Pec Deck Fly Exercise Guide: How To, Benefits, Muscles Worked, and Variations

Folks that have tried nailing a headshot on a head glitch or a constantly moving enemy (in Call of Duty, obviously) would agree that it can be both challenging and frustrating. The target is small and the surrounding stimuli too high. Your rear delts, also known as posterior deltoids, are not much different. They are placed at your back and are a tiny muscle group that is hard to isolate. 

Your back is the second-biggest muscle group consisting of muscles like the lats, traps, rhomboids, teres major and minors, and erector spinae. When you perform posterior-focused exercises, it can be hard to isolate the rear delts and ensure bigger and more dominating muscles like the lats and traps do not take over. 

And if this wasn’t enough, it is generally harder to establish a mind-muscle connection with your back muscles as you cannot look at them directly in the mirror while training. 

But why is training posterior deltoids important, you ask?

If you want to be a bodybuilder, you must focus on your overall physique aesthetics, including ensuring your musculature is symmetrical, proportionate, and balanced. Plus, you’ll never be able to achieve 3D shoulders if you don’t have well-developed posterior deltoids. 

Role of the real delts: Posterior deltoids help move your arms backward. Furthermore, they are used in many pulling movements and are important shoulder stabilizers.

Since your rear delts are a small muscle group that is hard to target, isolation exercises can help train them effectively. Enter the reverse pec deck fly, also known as the machine reverse fly. 

The reverse pec deck fly is one of the most popular but incorrectly performed exercises. However, we are here to fix this.  

This article sheds light on the muscles worked, benefits, correct technique, common mistakes, and variations of the reverse pec deck fly. 

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In This Exercise:

• Target Muscle Group: Rear Deltoids
• Secondary Muscles: Traps, rhomboids, teres major, and infraspinatus
• Type: Strength
• Mechanics: Isolation
• Equipment: Machine
• Difficulty: Beginner
• Best Rep Range: 10-15

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Muscles Worked: Reverse Pec Deck Fly

These are the primary and secondary muscles trained by this exercise:

Primary Muscles

The reverse pec deck fly is an isolation exercise that primarily focuses on the posterior deltoids. Maintain a slight bend in your elbows throughout the movement for an optimal rear delt engagement. Your arms shouldn’t be extended straight. On the other hand, don’t bend your elbows too much while performing this exercise. 

Secondary Muscles

Because the machine reverse fly involves pulling your elbows behind your torso, you’ll experience rhomboids, teres major, infraspinatus, and middle trapezius stimulation. However, if you feel greater activation in your other upper back muscles than the rear delts, you should limit your range of motion. 

How To Perform the Reverse Pec Deck Fly

This is how to perform the reverse pec deck fly using the correct form:

1. Adjust the handles of the pec deck machine in the reverse fly setting.
2. Sit on the machine with your chest against the pad. 
3. The handles of the machine should be in front of your shoulders.
4. Extend your arms straight in front of you and grab the handles with an overhand or neutral grip at shoulder height. 
5. Maintain a slight bend in your elbows throughout the movement. 
6. Open your arms in a reverse fly motion by contracting your rear delts. 
7. Your elbows should be behind your torso at the top. 
8. Pause and contract your rear delts for a second before slowly returning to the starting position. 
9. Repeat for recommended reps. 

Reverse Pec Deck Fly Tips

Here are a few tips to get the best bang for your buck while performing the machine reverse fly:

1. Do not let the weight stack at the bottom. It will ensure that there is constant tension on your rear delts throughout the set. 
2. Maintain an upright torso for the entirety of the set. A hunched back will take tension off your rear delts. 
3. Limit the movement to your arms. 
4. If you feel a scapular retraction, you are probably going too heavy. 
5. Keep your neck in a neutral position and look straight ahead. Do not look down or drop your head back while performing the exercise.
6. Prefer performing this exercise with a neutral grip as a 2013 study proved that keeping your hands facing inward significantly increases posterior delt activity. [2]

Read also pec deck guide.

Common Mistakes

Here are the most recurrent mistakes people make while performing the reverse pec deck fly:

1. Using Momentum

If we had to point out the biggest mistake people make while doing the machine reverse fly, it would be their use of momentum. How to know if you are using momentum? If you have to pull your chest off the pad at any point during the set, it is a sign you are cheating. 

Using a jerking motion takes tension off your rear delts and puts it on the more dominant upper back muscles like the traps and rhomboids. So, check your ego at the door before entering the gym, and do not use momentum to lift the weight by swinging your torso back and forth.

2. No Mind-Muscle Connection

While performing this exercise, most people go through the motions for the sake of it. They’ll put more weight on the machine than they can handle and rush through the movement just to achieve their rep target. 

However, you should focus on contracting your muscles with every rep if your goal is to build muscle mass. Pause at the top for a couple of seconds and squeeze the life out of your rear delts. 

You should lower the weights and slow down your rep tempo if you can’t achieve a rear delt pump or at least feel muscle contraction. Use a 2:2:4:0 rep tempo to annihilate your posterior delts. In this method, you’ll spend two seconds on the concentric motion, two seconds of contraction at the top, four seconds on the eccentric motion, and no rest at the bottom.

3. Slouching Your Back

Sit uptight while performing this exercise for optimal rear delt activation. Also, some people round their backs as they think it will help them achieve better stimulation at the bottom of the movement. However, doing so will result in greater activation of the teres muscles and rhomboids. 

Similarly, do not arch your back at the top in hopes of better posterior delt recruitment. Furthermore, looking down or up while performing this exercise also takes off tension from your rear delts. 

Benefits

Adding the reverse pec deck fly to your training regimen entails the following advantages:

1. Helps Build Shoulder Strength

Lifting weights help enforce strong shoulders, which translates to better performance in pushing and pulling exercises like the bench press, overhead press, and barbell row. Plus, it improves your day-to-day functionality. 

2. Enhances Aesthetics 

It is no secret that weight training for hypertrophy can help improve your aesthetics by toning and building muscle mass and definition. Posterior delt exercises give your shoulders a rounder and fuller look. 

3. Improves Posture

Since many folks spend the majority of their days hunched over a computer or phone screen, performing a back-fly movement like the machine reverse fly can improve their posture. 

4. Boosts Shoulder Mobility

The main role of the rear delts is to pull your shoulders back. Not only does regularly performing posterior deltoid exercises build strength and size, but it also improves shoulder mobility. 

Reverse Pec Deck Fly Sets and Reps

Unlike quads, hams, or lateral delts, the posterior deltoids are a relatively small muscle group and hence do not need a ton of volume and intensity to train optimally. 

We recommend performing 1-2 exercises in the 10-15 rep range with a picture-perfect form for rear delts in each workout. Anything over this would be overkill. Furthermore, you shouldn’t try to go too heavy on this exercise. Keep the weights moderate and focus on contracting your muscles with every rep. 

While many lifters like to perform the rear peck deck fly as a finisher, you could do this exercise at the beginning of your workout if your posterior delts are lagging compared to its other two siblings — the anterior and lateral delts. 

Reverse Pec Deck Fly Variations

Looking for more posterior deltoid exercises? Add the following lifts to your exercise arsenal to build 3D shoulders:

1. Bent-Over Dumbbell Fly

The bent-over dumbbell fly is one of the most popular free-weight posterior delt exercises and should be a part of your training regimen. 

How to perform:

1. Grab a dumbbell in each hand with a neutral grip (palms facing each other). 
2. Hinge from the hips until your body is almost parallel to the floor. 
3. Let your arms hang straight down from the shoulders so they are perpendicular to the floor.
4. While maintaining a slight bend in your elbows, pull the dumbbells towards the ceiling by performing a reverse fly using the rear deltoids.
5. Pause and contract at the top. 
6. Slowly lower the dumbbells to the starting position.
7. Repeat for recommended repetitions.

2. Standing Cable Reverse Fly

The standing cable reverse fly is done on the cable pulley machine, which helps eliminate inertia and keeps your posterior deltoids under constant tension throughout the motion. 

How to perform:

1. Position the pulleys at the highest setting.
2. Grab the cable on your left with your right hand and on the right with your left. 
3. You could also use a D-handle attachment. 
4. Take a couple of steps back until there is constant tension on the cables at the bottom. 
5. Extend your arms straight in front of you so they are parallel to the floor. This will be your starting position. 
6. Maintain a slight bend in your elbows.
7. Pull the handles laterally using your rear delts and without squeezing the shoulder blades together excessively.
8. Pause and contract at the top. 
9. Slowly return to the starting position and repeat for recommended reps.

3. Incline Bench Rear Delt Row

Although most people think rows only target the back, a few variations of this movement can also target the rear delts effectively. 

How to perform:

1. Set an incline bench at a 45-60 degree angle with the floor. 
2. Lie prone on the bench while holding a dumbbell in each hand with a pronated (overhand) grip. 
3. Extend your arms straight towards the floor. 
4. Lift your elbows towards the ceiling while keeping your upper arms perpendicular to your torso. 
5. Pause and contract your rear delts at the top. 
6. Return to the starting position using a controlled motion and repeat for recommended reps. 

4. Incline Dumbbell Rear Delt Fly

The incline bench dumbbell rear delt fly is a variation of the bent-over dumbbell fly (#1). This variation helps you better focus on your rear delts by removing your core and stabilizers from the equation. To get into position for this exercise, set up an incline bench at a 45-60 degree angle with the floor and use the same technique as the conventional rear delt fly to annihilate your target muscles. 

5. Face Pull

The cable face pull is a compound exercise that trains your rear delts, traps, and upper back muscles. 

How to perform:

1. Set the cable pulley at the highest setting and attach the rope attachment. 
2. Grab the ropes with an overhand grip from the outside. 
3. Take a step back and assume a staggered stance for better stability.  
4. Extend your arms straight in front of you so they are parallel to the floor. 
5. Pull the rope towards your face while keeping your upper arms parallel to the floor. 
6. Slowly return to the starting position and repeat for the desired number of repetitions.

6. Band Pull-Apart

This resistance band exercise is one of the most effective shoulder warm-up exercises you can do at the beginning of any upper-body training routine. 

How to perform:

1. Stand upright with a shoulder-wide stance and grab a resistance band with an overhand grip. 
2. Extend your arms straight in front of you so they are parallel to the floor. 
3. While maintaining a slight bend in your elbows, pull the band apart until it touches your chest. 
4. Slowly return to the starting position. 
5. Repeat for desired repetitions.

Frequently Asked Questions

Wrapping Up

Rear deltoids can be one of the most stubborn muscle groups. Furthermore, they are a lagging muscle group for most lifters as it is hard to isolate and establish a mind-muscle connection with them.

However, this is where the reverse pec deck fly shines. Use this exercise and the variations mentioned in this article to take your posterior deltoid gains to the next level. 

References

1. 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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