The chest, known technically as the pectoralis major, or pecs for short, makes up the major mass on the front of your upper body. As a large muscle group, it has a lot of areas to focus on: upper, lower, inner and outer.
Developing the outer pecs is important for developing wide, impressive pecs . . . think Arnold Schwarzenegger back in the day. To really build the outer pecs, you need to perform weighted exercises that place a lot of stretch on the pecs. One of the best exercises for placing stretch on the pecs is dumbbell flyes. Be sure to perform these with just a slight bend in your elbows so that your arms are almost straight during the movement. Also, go as low as possible in the bottom position . . . again, think Arnold. This works to target the outer-pec muscle fibers, which will build up to add more width to your chest.
WHEN TO GO WIDE:
To focus on the outer muscle fibers of the pectoralis major, do dumbbell flyes after doing major chest mass builders, such as bench presses and dumbbell presses.
FORM AND FUNCTION:
The pectoralis major is composed of two major heads.
The clavicular head, or upper pecs, starts on the clavicles (collar bones) and attaches to the humerus (upper-arm bone); the sternocostal head, or lower pecs, starts on the sternum and also attaches to the humerus. When the pectoralis major contracts, it moves the upper arm in numerous directions — such as toward the center of the body (adduction), during fl yes and presses; forward (fl exion), during reverse-gripbench presses; and down (extension), during pullovers.