Both the pec deck and the chest press, or the bench press, target the pectoralis major, commonly referred to as the pecs. The pectoralis major is above the stomach and below the clavicle. This muscle has two heads: the sternal head and the clavicular head. Both exercises directly target the sternal portion of the pectoralis major. Each exercise provides advantages and disadvantages.
On a pec deck machine, you press against two arm pads to move the weight. To begin, sit on the seat with your back against the back support, and place your forearms against the pads, also called levers, which are on each side of your shoulders. Your arms should be in a perpendicular position to the floor with your elbows bent at 90 degrees. Make sure your feet are flat on the floor, and push the arm pads toward the midline of your body, which brings them directly in front of your face. Pause for a moment as the arm pads touch each other in front of you, and return to the starting position. Choose a weight that allows you to comfortably perform this exercise for three sets of 10 to 12 reps.
The chest press, also known as the bench press, is traditionally done with an Olympic barbell and on a flat bench. To begin, lie flat on the bench with your feet firmly on the floor. Grab the bar with an overhand grip outside of your shoulder width. Push the bar off the rack, and slowly lower it to the middle of your chest. Stop when your elbows are lined up with your shoulders. Push the weight back up as you fully extend your arms, but do not lock out your elbows.
Choose a weight that comfortably allows you to perform this exercise for three sets of 10 to 12 reps. The chest press can also be done with dumbbells or on a chest press machine. Both exercises are performed in the same fashion except the chest press machine is done in a seated position with your head and back against a padded back support.
Pectoralis Minor and Serratus Anterior
The pec deck has one distinct advantage over the chest press in that it requires the smaller chest muscle, known as the pectoralis minor, to play a role in the movement. The pec deck also requires the serratus anterior, which is just below the pectoralis minor, to assist in the exercise movement. These muscles assist in the movement but are not directly targeted. The chest press does not require either of these two to be involved. Exercising these two muscles can give your ribcage a well-defined and muscular appearance.
The chest press places more of a strain on the shoulder joints than the pec deck due to the movement of pushing the weight upward. The pec deck impacts joints less and does not cause shoulder issues like the chest press. Additionally, the chest press can cause neck strains if you lift your head off the bench when performing the pressing motion. The pec deck does not place additional strain on the neck muscles, which means you won't sustain a neck muscle injury if your head comes off the pad when executing the movement.
Maximum Strength and Power
The chest press is a more powerful movement and is traditionally used to develop larger chest muscles and maximum power. It is one of the three main exercises for powerlifters along with the squat and deadlift. The pec deck is traditionally considered to be an exercise that creates more definition in the chest but is not used for developing maximum chest strength, power and size.