What Muscles Does the Pec Fly Machine Work?

Sometimes you want to work out your chest without loading heavy plates onto a bar or heaving bulky dumbbells. In that case, turn to the pec fly machine, also sometimes referred to as the pec deck.

This machine features a padded seat and back rest from which two levers protrude. You sit in the seat and place your arms into the padded levers, drawing your elbows together like you're flapping your wings.

The machine emphasizes your pectoralis major muscle, the broad muscle of the chest, as well as a few helper muscles. It has minimal reach when it comes to muscle activation, though, as it's an isolation exercise, activating just one joint.

Read more: 12 Cable-Machine Moves that Build Muscle and Torch Calories

The bench press is considered the top exercise when it comes to training your pectoralis major, but the pec deck or chest fly machine is a close second. An October 2012 study sponsored by the American Council on Exercise found it to be 98 percent as effective as the standard flat-bench press in recruiting the pec major.

The pectoralis major fans over the front of your chest wall. It allows you to swing, flap, push and bring your arms together. Strong pecs create a lifted torso, making your posture and confidence soar.

The smaller pec minor also gets a workout during a set on the pec fly machine. This muscle lies underneath your pec major and is responsible for stabilization of your shoulder blade.

The serratus anterior is responsible for opening up the backs of your shoulders to bring your arms forward, as in a punch, or when you're pulling your arms together in a chest fly. It's not the primary muscle activated during the pec fly machine move, but it does play a role.

You'll also feel the fronts of your shoulders activate while using the pec fly machine. The anterior deltoid muscle helps bring the arms of the pec fly machine together. If you straighten your arms, or use a machine model with handles and longer levers, the fronts of the shoulders as well as the upper chest will get even greater activation.

The pec fly machine also activate your ab muscles as they contract to help stabilize your upper body as your arms move.

Read more: Major Muscle Groups Used in Bench Press

When you don't have access to a pec fly machine, a simple dumbbell fly is a perfect substitute. If you're on the road, pack a resistance band and use it to perform flyes. Simply hook it around a stable pillar, hold a handle in each hand at chest height and pull your hands together as if you're performing a hug.

If you do have access, include the pec fly machine with the chest press and bent-forward cable crossovers to do a complete workout for your chest. Aim for two to three chest workouts per week, as part of a total-body conditioning program. Start with just one set of eight to 12 reps; work up to three or more, if your goal is to build muscle.