Machine Reverse Fly
What Is the Machine Reverse Fly?
Machine Reverse Fly is an isolation exercise that primarily targets the rear deltoids (rear head of the shoulders) and also engages the middle trapezius, rhomboids, and the infraspinatus and teres minor on the back of the shoulder. It is a beginner-level movement performed on a reverse pec deck machine, which provides stability and controlled movement, making it easier to maintain proper form compared to free weights.
The main purpose of the exercise is to build size and strength in the often-neglected rear delts, which get far less direct work than the front and middle heads in most pressing-heavy programs. It adds posterior shoulder and upper-back volume that balances out a high number of presses, and it rounds out the look of the shoulders from the side and back. It is usually programmed as an accessory after the main compound lifts in a shoulder, back, or upper-body session.
Unlike free-weight versions such as the Dumbbell Rear Delt Fly, where the load is lightest while the arms hang down and heaviest as they reach shoulder height, the machine's lever arms keep resistance on the rear delts from the very start of each rep, although how the load feels through the arc depends on each machine's cam and lever design. The seat and chest pad hold the torso still, minimizing the risk of momentum-based errors. The machine also allows for precise weight selection, making it accessible for beginners and effective for more advanced lifters focusing on rear delt hypertrophy.
Handle position shifts the emphasis. Many reverse pec deck machines have both horizontal handles, held with an overhand grip, and vertical handles, held with a neutral grip with the palms facing each other, and a study of resistance-trained men on a reverse fly machine found that the neutral grip produced more rear deltoid and infraspinatus activity than the overhand grip. Squeezing the shoulder blades together at the end of each rep brings in more of the middle trapezius and rhomboids, while keeping them still and moving only at the shoulder concentrates the effort on the rear delts. Because the traps readily take over when the weight is too heavy, a moderate load and a deliberate focus on the back of the shoulder matter more here than on most machines.
The exercise suits beginners learning to train the back of the shoulder, lifters working toward fuller and more balanced shoulders, and anyone whose program is built heavily around pressing. If even the lightest setting on the stack is too heavy, Band Pull Apart and Band Reverse Fly train the same arm path against lighter resistance.
Muscles Worked
- Deltoid
- Primary
- Infraspinatus
- High
- Teres Minor
- High
- Lower Trapezius
- Medium
- Rhomboid Major
- Medium
- Teres Major
- Low
- Triceps Brachii (Long Head)
- Minimal
Instructions
- Adjust the seat height so that the handles are at shoulder level when seated.
- If the machine arms adjust, set them so the handles start directly in front of you.
- Sit with your chest pressed against the pad and grab the handles with your arms extended in front of you, using a pronated grip on the horizontal handles or a neutral grip on the vertical handles.
- Keep a slight bend in your elbows and engage your core.
- Slowly pull the handles outward and back until your arms are in line with your shoulders.
- Pause briefly at the end of the movement, keeping your shoulders down and your shoulder blades still rather than pinching them together.
- Slowly return to the starting position in a controlled manner.
- Repeat for the desired number of repetitions.
Common Mistakes
Using Too Much Weight
Going too heavy can lead to improper form and reduce rear delt activation.
Setting the Seat at the Wrong Height
A seat that puts the handles well above or below shoulder height pulls your arms off a level path, and handles set too high let the upper traps take over.
Shrugging the Shoulders
Allowing the traps to take over minimizes rear delt engagement.
Swinging the Arms
Using momentum, including letting the weight stack slam between reps, reduces the effectiveness of the exercise.
Bending the Elbows Into a Row
Bending the elbows more as you pull turns the fly into a row that lets the biceps and back muscles help, so hold the same slight elbow bend from start to finish.
Pinching the Shoulder Blades Together
Squeezing the shoulder blades together to pull the handles back past your torso shifts the work to the rhomboids and middle traps, so keep them fairly still and stop when your arms are in line with your body.
Injuries
Machine Reverse Fly is a low risk exercise when performed with proper technique. However, improper execution or excessive weight can lead to strain. The chest pad and fixed arm path remove most of the balance and lower back demand, so problems usually trace back to seat setup, load, or letting the machine control the arms.
Lifting too heavy or using improper form can place excessive stress on the shoulder joint. Always use a weight that allows for controlled movement. Set the seat so the handles are at shoulder height when you grip them, and finish each rep when your arms are roughly in line with your body rather than forcing them further back, which pushes the front of the shoulder forward. Return the handles under control instead of letting the stack pull your arms forward past a comfortable stretch, and keep your shoulders down so the work does not shift into your upper traps and neck.
Keep your chest against the pad to ensure stability. Pulling your chest off the pad to swing the handles open replaces rear delt work with momentum and can irritate the lower back. Elbow and wrist discomfort usually comes from locking the elbows hard under load or squeezing the handles too tightly. Maintain a firm but relaxed grip and keep a slight bend in your elbows.
If the lightest pin still feels too heavy or your shoulders are irritated, start with Band Pull Apart or Lying Prone T Raise, which train the same pattern with a lighter load. Once you can control the machine for full sets, free-weight and cable versions such as the Dumbbell Rear Delt Fly and Cable Reverse Fly add the challenge of holding your own torso position without a pad. Stop the set if you feel sharp or pinching pain in the front or top of the shoulder, or numbness or tingling down the arm, and have persistent pain checked by a qualified professional.
Other Names for the Machine Reverse Fly
The Machine Reverse Fly is also known as:
- Reverse Pec Deck
Frequently Asked Questions
- Q: Is the machine reverse fly better than dumbbell reverse flys?
Both exercises are effective, but the machine reverse fly offers more stability and controlled resistance, making it easier to maintain proper form. Dumbbells load the movement mostly near the top, where your arms are level with the floor, while the machine keeps tension on through the whole arc, and the Dumbbell Reverse Fly is a good substitute when no machine is free.
- Q: How many reps should I do?
Aim for 10 to 20 reps per set with a weight you can move through the full range without shrugging or swinging. This small movement responds well to moderate loads taken close to failure, while loads heavy enough to keep you under 10 reps usually shift the work to momentum and the upper traps.
- Q: Can this exercise help with posture?
It can contribute, but not on its own. Strengthening the upper back is a sensible part of a program for rounded shoulders, usually alongside chest and shoulder stretching and attention to daily habits, but a single exercise is not a proven fix for how you sit or stand.
- Q: How do I set up a pec deck for reverse flys?
Set the seat so the handles line up with your shoulders when your chest is against the pad, and if the machine arms adjust, set them so they start directly in front of you. Hold the horizontal handles with your palms facing down, or the vertical handles with your palms facing in if that feels better on your shoulders.
- Q: Can the machine reverse fly replace rows?
No. Rows are compound pulls that train the whole upper back and arms with much heavier loads, so use the machine reverse fly alongside a row such as the Cable Seated Row, not instead of one.