The Muscles Used in a Pec Deck Machine

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.

The pec deck is an effective chest strengthener. (Image: Antonio_Diaz/iStock/Getty Images)

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. (Image: 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.

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. (Image: 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.

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