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The Muscles Used in a Pec Deck Machine

author image Andrea Cespedes
Andrea Cespedes is a professionally trained chef who has focused studies in nutrition. With more than 20 years of experience in the fitness industry, she coaches cycling and running and teaches Pilates and yoga. She is an American Council on Exercise-certified personal trainer, RYT-200 and has degrees from Princeton and Columbia University.
The Muscles Used in a Pec Deck Machine
The pec deck is an effective chest strengthener. Photo Credit: Antonio_Diaz/iStock/Getty Images

If you throw, push or swing your arms, you want strong pecs. This muscle, formally known as the pectoralis major, covers the upper torso area in a fan-like shape. Exercises to work this area include the bench press, push-up and pec deck.

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What is the Pec Deck?

The peck deck, a weight machine, consists of a platform upon which you sit. Protruding from a bar behind the seat are two levers that you pull toward each other. When you do, you'll feel your upper body muscles squeeze together, eliciting action in the pectoralis major.

How To:

  • Sit on the platform with your back pressed into the back pad. 
  • Place your forearms against the pec deck levers or hold the handles -- which one you do depends on the model you have available. 
  • Pull your arms toward each other and release until you feel a stretch to complete one repetition. 
Some machines feature handles instead of arm pads.
Some machines feature handles instead of arm pads. Photo Credit: LUNAMARINA/iStock/Getty Images

Muscles Engaged

Because only one joint is used in the pec deck action, it's considered an isolation exercise. No real stabilizing muscles are activated; the machine acts as a stabilizer.

Pectoralis Major: The pectoralis major attaches at the clavicle -- up near the collar bones -- and at the sternum, the bottom of the breastbone. In women, this muscle lies mostly underneath the fatty breast tissue. The pec deck fly primarily targets the sternal, or lower, region of the muscle, but the upper portion of the muscle does assist in the action.

Pectoralis Minor: This is a thinner, flatter muscle that lies underneath the pec major. It provides assistance to your pec major during the pec deck flye by keeping your shoulders from shrugging upward.

Serratus Anterior: Your serratus anterior lies along the sides of your chest wall, right above the first eight ribs. A strong serratus anterior provides power to punching and swinging actions.

Exercise Effectiveness

The pec deck is nearly as effective as the bench press in activating the pectoralis major, found a 2012 study sponsored by the American Council on Exercise. It's superior to several variations of the push-up, weighted incline flyes and dips when it comes to activating the primary action of the chest muscles.

Read More: Pec Deck Vs. Chest Press

Golfers particularly benefit from the muscles trained by the pec deck fly, showed a study published in a 2009 issue of the Journal of Strength and Conditioning Research. Other athletes that appreciate the functional gains achieved by using the pec deck include tennis players and boxers.

The pec deck works by squeezing your upper body muscles against resistance.
The pec deck works by squeezing your upper body muscles against resistance. Photo Credit: DrDjJanek/iStock/Getty Images

Multiple Exercises Bring Best Results

While the pec deck is effective in training your chest, you'll develop the most muscle from performing two or three exercises per muscle group to stimulate the muscle fibers from different directions. To get the most out of your chest workouts, include the pec deck fly along with the bench press and bent-over cable crossover flyes.

Read More: Lean Muscle Chest Workout

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