Written by Patrick Dale, PT, ex-Marine

There is perhaps no better exercise for your posterior deltoid and back than the cable rear delt fly.   If you put all the muscle groups in order of importance, most bodybuilders would place the rear or posterior deltoids at the bottom of the list.

The rear delts are a small muscle, and yet it could be argued that they’re one of the most important. When properly developed, the rear link in with your lats, traps, and rhomboids together to create an impressive-looking back.

As well as being important for aesthetics, the rear delts play a crucial role in the health and function of your shoulder joints. Weak rear delts are a leading cause of shoulder pain.

Unfortunately, the rear delts aren’t just out of sight and out of mind. They’re often undertrained simply because they aren’t involved in all that many upper body exercises.

The anterior deltoid, which opposes the rear deltoid, is involved in all chest exercises and shoulder pressing exercises. A lot of lifters also train this muscle with dumbbell, barbell, and front raises. It’s rare to find a bodybuilder with underdeveloped anterior delts.

In contrast, the rear deltoid is only really active during pulling exercises with your arms raised, e.g., wide-grip bent-over rows and face pulls. So, if you want to train your rear delts, you have to do so more purposely.

There are several effective ways to train your posterior deltoids, but the rear delt cable fly is one of the best.

In this article, we explain why and how to do this exercise and reveal the ten best variations and alternatives.

Technically, the rear delt cable fly is an isolation exercise. That means movement only occurs at one joint. However, despite being a relatively straightforward movement, the rear delt cable fly affects several important muscles:

Posterior deltoid – located on the back of your shoulder joint, the posterior deltoid is responsible for horizontal shoulder extension and shoulder extension with your arm lowered. The rear deltoid is usually the least well-developed of the three deltoid heads, with the others being the anterior (front) and medial (side).  

Trapezius – known as the traps for short, this is the large kite-shaped muscle of the upper back. Rear delt cable flys hit the middle fibers of the traps, which are responsible for pulling your shoulder blades back and together in a movement called retraction.

Rhomboids – located between the shoulder blades and beneath the trapezius, the rhomboids also pull your shoulders back and together in retraction. The mid traps and rhomboids are critical postural muscles, and strengthening them can help prevent slouching.

Triceps brachii – usually known simply as the triceps, this three-headed arm muscle works with the rear delts to extend your arm backward. However, while you may feel your triceps working during rear delt cable flys, this is definitely more of a shoulder exercise than an arm builder.

Rotator cuff – the rotator cuff is a group of muscles and tendons that keep the shoulder joint stable. These muscles also allow the shoulder to rotate safely. It’s made up of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. While not a member of the rotator cuff group, teres major is also involved during rear delt cable flys.

Get more from cable rear delt flys while keeping your risk of injury to a minimum by following these guidelines:

This exercise is best done using light to moderate weights and medium to high reps. It does not work well with heavy weights and low reps.

Are you unsure if rear delt cable flys deserve a place in your workouts? Weigh up these benefits and then make your decision:

Better posture – posture is the alignment of your joints, and it can be good or bad. The pull of gravity, combined with too much time sitting and too much chest training, means that a lot of lifters have poor posture. Adding cable rear delt flys to your upper body workouts can help fix your slouch.

A straightforward exercise – while there are other rear delt exercises you can do, cable rear delt flys are one of the simplest. This exercise is easy to learn, quick to master, and ideal for beginners.

No lower back stress – unlike some freeweight posterior deltoid exercises, rear delt cable flys are done in a standing position. As such, there is very little lower back stress to worry about. This exercise is suitable for most lifters, even those suffering from low back pain.

The perfect superset with cable crossovers – rather than just rest between sets of cable crossovers for your chest, why not alternate with sets of cable rear delt flys? This makes better use of your time and ensures that your upper body workout is balanced.

While cable rear delt flys are a mostly beneficial exercise, there is also a drawback to consider:

You need access to a cable crossover machine! – while most gyms have cable crossover machines, you may not have access to one if you train at home or in a garage gym. However, there is no need to neglect your rear delts; there are plenty of non-cable machine alternatives you can do instead.

Cable rear delt flys are a highly effective shoulder and upper back exercise, but that doesn’t mean you need to do them all the time. There are several variations and alternatives you can use to keep your workouts productive and interesting:

Training each arm independently may seem like a waste of time, but you will probably find that you can lift more weight or do more reps compared to the two-armed version. You should also find that your mind-muscle connection is stronger. This is also a good option if you can’t use a cable crossover machine but still have access to a single high cable device.

This exercise is basically the same as regular standing cable rear delt flys. Still, some people prefer it and find it more comfortable. However, make sure you hinge from the hips rather than round your lower back, as doing so can lead to injury.

No cable crossover machine? No problem! You can work your rear delts with a pair of good old-fashioned dumbbells! You can do bent-over reverse dumbbell flies standing, seated, or prone on an exercise bench.

Regardless of the option you choose, this is an effective if somewhat challenging posterior deltoid exercise. Don’t go too heavy, or you’ll end up using your back more than your dear delts.

The reverse pec deck guides your movements, so you are free to focus on pushing your rear delts and upper back to their limit. This is a valuable exercise for bodybuilders looking to maximize hypertrophy. Like reverse cable crossovers and regular cable crossovers, this exercise makes a great superset with the pec deck done in the usual way.

Most pressing exercises work your anterior deltoids more than your rear delts. That all changes when you do prone incline dumbbell presses. This exercise is much more challenging than it looks, so don’t go too heavy too soon!

The cable supine reverse flye is an effective isolation exercise for the posterior deltoids. Done face up on a flat bench, it provides lots of support for your lower back and also stops you from cheating as you cannot use your legs or upper body to help raise the weight.

If there is one rear delt exercise that every lifter should do, it’s band pull-aparts. Keep a resistance band in your gym bag and do them as part of your upper body warm-up or between sets of bench presses.

You can even do this exercise at home to break up long periods of sitting. Band pull-aparts are THE most excuse-free way to train your rear delts and improve your posture.

Face pulls target your entire upper back, i.e., the mid-traps, rhomboids, AND posterior deltoids. They’re an excellent postural exercise and one that could add some thickness to your upper back muscles. Face pulls are also good for your shoulder health and could help ward off shoulder joint pain.

However, to get the best possible results, make sure you keep your arms up and really drive your elbows back. If you don’t, you could end up using your lats more than your rear delts and traps.  

Related: Best Face Pull Alternatives

No barbell, cable machine, or resistance band? No problem! You can train your posterior deltoids using just your body weight for resistance. Inverted rows are typically thought of as a lat exercise but, done with a wider grip, they’re also an excellent move for building the posterior deltoids.

Just make sure you pull your chest to the bar to fully engage your rear delts. If your elbows drop, your lats will end up doing more work than they should.

This dumbbell row variation works your rear deltoids, middle trapezius, rhomboids, and biceps instead of the more usual lats. The trick is to keep your elbows up and away from your body, so your arms are abducted and perpendicular to your body.

Your lats will take over if you let your elbows drift down toward your sides, so KEEP ‘EM UP!

There are three deltoid heads – anterior, medial, and posterior – and they all need to be trained pretty equally to build an aesthetically pleasing and structurally solid upper body.

There are plenty of rear deltoid exercises to choose from, but the cable rear delt fly is among the best. You can do it as part of your shoulder workout or when you train your back.

Regardless of when you do it, this exercise will help strengthen and build your underused, underdeveloped posterior deltoids, and it deserves a place in your workout library.

Patrick Dale is an ex-British Royal Marine, gym owner, and fitness qualifications tutor and assessor. In addition, Patrick is a freelance writer who has authored three fitness and exercise books, dozens of e-books, thousands of articles, and several fitness videos. He’s not just an armchair fitness expert; Patrick practices what he preaches! He has competed at a high level in numerous sports, including rugby, triathlon, rock climbing, trampolining, powerlifting, and, most recently, stand up paddleboarding. When not lecturing, training, researching, or writing, Patrick is busy enjoying the sunny climate of Cyprus, where he has lived for the last 20-years.

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