February 24


Chest Fly Machine | Step-by-Step Guide | How to Do the Pec Deck

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Knowing how to do a chest fly properly on the pec deck machine can greatly improve your gym physique. It's one of those machines where you see all manner of guys and girls giving it a go, with mixed results. So if you really want to know how to do it properly and up your chest game, read on.


The pec deck is one of the most popular machines in the gym. With the correct tech­nique, it provides a great way to work the chest muscles with pec flyes. It's perfect for those who like the simplicity, speed and ease of use provided by a machine.

Additionally, when performed correctly can be every bit as effective at hitting those chest muscles as free weights exercises.

What are pec deck flyes?

Pec flyes are normally performed on a machine, commonly known as the pec deck.

By sitting in an upright position and bringing the elbows across the chest while exerting force against pads and levers with the forearms, the pec­toral muscles of the chest can be worked.

Unlike the chest press machine, which uses the triceps muscles of the arm to assist the chest, pec flyes when executed correctly, hone in on and isolate the pectoral muscles of the chest.

Why perform flyes on the peck deck?

Pec flyes isolate and work the chest muscles. These are used in any activity where the arms move forward or across the torso.

Examples include racquet sports, swimming, gymnastics and numerous other sports. Additionally, any ac­tivity that requires 'pushing' with the arms.

Also, correctly performed chest exercises can improve posture and breathing. Furthermore, they'll lend an aestheti­cally pleasing look to the upper torso.

Apart from increasing the variety in your armoury of chest exercises, pec flyes can also be an excellent tool for de­veloping flexibility. Both in the pectoral muscles of the chest and the shoul­der joint. The muscles and joints are worked through a much larger range of movement than normal 'pressing' movements for the chest.

How to perform the machine chest fly correctly and safely

Body position

Sit on the pec deck with your back flat against the upright and place your hands on one of the handgrips. Secondly, make sure your forearm is pressed against the support pad.

Now check the height of your elbow in the mirror (or ask someone to observe it for you). Your elbow must be at about the same height as your shoulder and certainly no higher. Ideally, you want your elbow somewhere above the nipple and marginally below shoulder height.

Viewed straight on in a mirror, your upper arm will be just about parallel to the floor.

If your elbow is higher than shoulder height, move the seat upwards. Conversely, if it's lower, move the seat down a little. Some pec decks also offer variable handgrips.

Arm lever start position

Many modern pec decks provide a variable range of movement. You can take advantage of this to work your chest muscles through a full range of movement and to improve your shoulder joint flexibil­ity.

Having sorted your optimum body position, sit right back on the seat. Next, en­sure your head and back are flat against the upright. Then, try simultaneously to place both arms in position, hands on the grips and forearms behind the pads.

If you can manage this, the range of movement set is not sufficient for you. You need to set the levers further back so that when you attempt to position both arms as described above, you can't quite stretch to it.

If the levers are still miles behind you even when you're fully stretched, you'll need to bring them in a bit.

The ideal lever starting position is about three inches, or 7.5 cm, behind your maximum stretch.

Getting started

OK, now you're ready to start. And you thought all you had to do on the pec deck was to adjust the weight.

After selecting the cor­rect weight, sit right back on the seat. Turn your torso slightly to your right and pop your right arm in the correct position behind the pad.

Now turn to­wards the left lever, dragging the right lever in a little as you turn. You should now find that you're able to place your left arm behind the left pad with ease.

Having got both arms in position, turn to face forwards again. Make sure you're sitting right back on the seat, with your head and back fully sup­ported.

The lifting phase

Gripping the handles only lightly, squeeze the levers in­wards.

Make sure that all the force for the movement comes from the pres­sure on the pads applied by the forearms. Don't push with the hands.

Squeeze until the two pads meet directly in front of you. You want both pads to travel the same distance. However, you may find that your weaker side lags behind the stronger side. That's ok, for now.

When the two pads touch directly in front of you, pause briefly in this position. You're at the point of maximum contraction, so squeeze your chest mus­cles.

Keep your back and head flat against the seat upright throughout the lifting movement. Avoid leaning forward, especially as you reach the maximally contracted position.

You should be breathing out during the lifting phase.

The lowering phase

Slowly and smoothly, let the levers move backwards.

Ensure that they're moving at the same speed as each other and inhale dur­ing this movement.

You should allow the levers to move back far enough so that you get a really full-range movement. You want your chest to feel thoroughly stretched before coming back for the next rep.

However, to accomplish this safely, you must concentrate on a smooth, steady lowering action. Don't let the levers suddenly fly back out of control. That's a shoulder injury waiting to happen.

What variations on the machine chest fly are there?

Some pec deck machines allow you to tilt the angle of your torso.

By moving the seat back from a vertical position to a more reclined position, the emphasis of the exercise moves towards the upper region of the pectoral muscles.

Other pec machines lack pads on which to rest the forearms. Instead, the levers have a more universal type of movement.

Two to three high-quality sets of 10-12 reps are all you'll ever need.

The idea is to simulate more closely dumbbell chest flyes — the free weight version of pec flyes.

While there are some benefits to freer motion, the lack of forearm pads means there's also more scope for getting it wrong. For instance, you're more likely to involve other muscles such as the biceps and triceps of the arms. And the shoulder muscles too for that matter. This makes them less suitable for beginners.

The same is true for cable flyes, performed on a cable crossover machine.

In this case, you pull handles attached to cables across the chest, while lying flat on a bench. Unless you've plenty of previous experience, the standard pec deck is as good a place as any to get the feel for pec flyes.

How should I construct a pec deck routine?

Remember the imperative for a full-range movement. You should select your weight so that you can just complete around 10-12 reps before becoming fatigued.

Avoid the temptation to increase the weight and cut back on your range of movement.

While it may look impressive, you won't be reaping the full potential benefit of this exercise. Two to three high-quality sets of 10-12 reps are all you'll ever need. That is, providing the form is strict and you work to exhaustion on each set.

Which muscles are used in the pec deck movement?

When pec flyes are performed correctly, the pectoral muscles (A) are effectively isolated.

Anatomical diagram showing how different portions of the pectorals are activated during the chest fly machine or pec deck

Generally, the outer pectorals (clavicular pecs (C) ) are more active when the levers are brought back behind the line of the torso. On the other hand, the inner or sternal portion of the pecs (B) is active when the levers are brought close together. That is, at the point of maximum contraction (and during the squeezing motion mentioned above).

Is the pec deck on a chest fly machine effective?

The machine chest fly allows you to work your major chest muscles simply and effectively. With selector pins, you can tailor the exercise to your current fitness and strength level by adjusting the weight. It's a good exercise to help build muscle mass in the chest area. Having said that, you'll get more growth from barbell bench press variations. However, a machine chest fly on the pec deck will strengthen your shoulders and core muscles too.

How should I integrate pec deck flyes into my workout?

Like all isolation exercises, the pec deck machine chest fly is not a mass-builder. It's more of a refining and strengthening exercise.

So you're better doing two to three sets only AFTER you've done your main chest strengthening work. It's a good idea to do your compound movements first. For lifts such as bench press, you really need to be fresh.

The exception to this rule of thumb is when you want to pre-exhaust the chest during a very intense workout.

Perform an isolation set of pec flyes and your chest muscles will become quite fatigued. By immediately following the flyes with a compound movement like bench or chest press, the triceps, which are still fresh, can help drive the chest muscles into a very deep state of exhaustion.

Repeating this sequence two or three times will give your pectoral muscles a workout to remember. However, be warned - it's not for the faint-hearted!

Chest exercises can improve posture and breathing as well as lend an aesthetically pleasing look to the upper torso.

Apart from increasing the variety in your armoury of chest exercises, pec flyes can also be an excellent tool for developing flexibility. Both in the pectoral muscles of the chest and the shoulder joint. The muscles and joints work through a much larger range of movement than normal 'pressing' movements for the chest.

Top Tips to Perform Pec Deck aka the Chest Fly Machine Properly

Although flyes performed on a pec deck machine appear relatively simple, it's surprising how many people get it wrong. Even experienced trainers can do with some technique cues and refreshers now and again.

t's crucial to get the seat height right before you start your pec deck set

Seat Height

It's crucial to get this right. If you don't, you won't be comfortable and you won't achieve a full range of movement.

All the pressure to move the levers of the chest fly machine must come from the forearms on the pads

Use your Forearms

All the pressure to move the levers must come from the forearms on the pads. If you use your hands to push the hand-grips, you'll start using your triceps muscles. This is not what you want. You perform pec flyes to isolate the pectoral muscles.

To avoid falling into this trap, try resting the palms of your hands on the grips, rather than gripping.

Sit upright while performing the pec deck and avoid leaning forwards to keep the emphasis on your chest muscles

Don't lean forwards while doing the pec deck machine chest fly

It's very tempting, especially when you fatigue, to lean forwards for a bit of extra leverage.


You'll shift the emphasis away from the chest. Moreover, craning or lunging your upper body forward is not good for the back.

Once you can no longer squeeze the levers to the centre without cheating, you've successfully exhausted the chest muscles. Therefore, you should finish the set.

Use a sensible weight as pec flyes are an isolation exercise, where the quality of movement is the key to success

Use a sensible weight on the chest fly machine

It may look macho to pile on the weight. However, if you can't execute at least 9-10 full-range reps using the form described above, you're wasting your time.

Remember that pec flyes are an isolation exercise, where the quality of movement is the key to success.

If you've any history of shoulder or pectoral injuries, you're better off setting the levers of the chest fly machine to a more forward position


If you've any history of shoulder or pectoral injuries, you're better off setting the levers to a more forward position. As a result, you're effectively lowering the range of movement. Consequently, you reduce the possibility of overstretching during the movement.

If in doubt, consult your GP or physiotherapist.

Did you enjoy this article?

I'd love to know if you found this helpful or not, so drop me a comment below. Likewise, if anything's unclear or you have an idea for other content you'd like to see me put together, get in touch.

Paul Stokes Perth Personal Trainer Sports Nutritionist Group Fitness Instructor Massage Therapist

About the author

Paul Stokes

Paul Stokes BSc (Hons) is a Certified Personal Trainer, Accredited Sports Nutritionist, qualified Exercise to Music Instructor, Precision Nutrition coach, Massage Therapist and teaches 8 of the Les Mills Group Exercise programs.

He currently works in the Oil & Gas industry as a Wellness Coach, imparting his vast knowledge and experience to improve the quality of life of several hundred offshore workers.

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