The Pec Deck Fly exercise is an isolation exercise commonly used to develop the chest (pectoral muscles). The Pec Deck Fly (Butterfly) main advantage is sets can be done quickly because all that is needed to change the weights is a pin, and the exercise can be done safely, since less balance and control is required.

Pec Deck Fly Overview

• Main Muscle(s) Worked: Pectoralis Major, Sternal
• Other Muscles Worked: None
• Equipment: Pec Deck Machine
• Mechanics Type: Isolation (an exercise that involves just one discernible joint movement).
• Push: Push (A movement away from center of body during the concentric contraction of the target muscle.
• Utility: Auxiliary (An optional exercise that may supplement a basic exercise. Auxiliary exercises may place greater relative intensity on a specific muscle or a head of a muscle).

Target Muscles Used Pec Deck Fly (Butterfly)

• Pectoralis Major, Sternal

Synergist Muscles Worked When Performing the Pec Deck Fly

• Deltoid, Anterior
• Pectoralis,Clavicular

How to Properly Perform the Pec Deck Fly

• Sit in the pec deck flyes machine with your back against the seat.
• Place your forearms on padded lever.
• Position your upper arms approximately parallel to the floor.
• Push your arms in front of you in an arc fashion slowly and squeeze your chest in the middle until your elbows meet in front of your chest.
• Return to the start position with your chest muscles stretched fully.
• Repeat.

Tips for Performing Pec Deck Fly

• Do not move in a jerky or uncontrolled manner.
• Remember to push with your elbows and not hands.
• Be sure to really squeeze your pecs in the contracted position for a count of two.

Common Errors While Performing the Pec Deck Flyes 

• Using too much weight where you can't hold in the contracted position for the count of two.
• Uncontrolled motion when returning to start position.
• Hyper extending your shoulders at the starting position.
• Performing the movement too fast doesn't allow you to fully recruit as many muscle fibers.

Variations of the Pec Deck Fly

• Pec Fly with Dumbbells.
• Chest Press Machine
• Pec Fly with a Resistance Band.
• Pec Fly with Cables.

Bottom line

The Pec Deck Fly is a great finishing isolation exercise and compliments compound movement exercises like the barbell bench and dumbbell bench press very well. It can be done quickly, doesn't require great balance and is one of the safest chest exercises that can be performed in the gym.

About the Author 

Lynn Glenn is a 61 year old natural athlete who started training at the ripe young age of 48. Lynn Glenn is also an avid weightlifter who enjoys writing about hot topics in the areas of health, and fitness and developing further knowledge in the areas of disease prevention, nutrition, anti aging and personal training. Lynn Glenn lives and trains in Southern California, and serves as a tremendous inspiration for many "mature" weightlifters in the gym that are trying to look better, feel better, and beat father time!