The ACE says the bench press works your pecs effectively.
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The bench press is one of the most commonly practiced weight training exercises. It is generally used to improve upper body strength and tone, strengthen, or build up the pecs. To effectively work your pecs with the bench press, don't overtrain by doing too many sets, avoid using excessively heavy weights that you can't control, and perform the exercise with correct technique.
Targeting Your Pecs
Your pectorals major, or pecs, are made up of the sternal head or lower pecs and the clavicular head or upper pecs. The bench press targets both heads of your pecs. To perform the barbell bench press, lie on a flat bench and grasp a barbell with shoulder-width grip. Lower the barbell with your elbows pointing downward to just above your nipple line, touch the bar lightly to your chest, then push it above your head until your arms are fully extended. Keep your feet firmly on the floor, and your back firmly pressed against the bench. Alternatively, perform the bench press using a resistance machine, Smith machine, or dumbbells. Resistance machines and the Smith machine balance the weights, compelling you to move the bar along a pre-determined path. Dumbbells allow you to work each pec unilaterally.
The Training Effect
The precise effect the bench press has on your pecs depends on your training regimen. ExRx.net recommends heavy weights for sets of six to 12 reps to build muscle. To tone and strengthen your pecs, use 30 to 60 percent of your one-rep maximum for eight to 12 reps. To improve muscular endurance, use 40 to 60 percent of your one-rep maximum for 12 to 15 reps.
Some exercise professionals believe the bench press doesn't effectively work your pecs, with your triceps and anterior deltoids bearing most of the workload. However, a study by the University of Wisconsin, La Crosse, sponsored by the American Council on Exercise, determined that the bench press is a highly effective pectoral exercise. Using electromyography equipment, the study found that the barbell bench press activates more pectoral muscle fibers than other chest exercises such as pushups and dips.
Other Pec Exercises
Isolation exercises such as dumbbell bench flys, pec dec flys and cable crossovers minimize any involvement of your triceps and anterior deltoids, allowing you to focus on your pecs. These exercises mimic the the main function of the pecs, which is to pull your upper arm across your chest. The ACE sponsored study ranked pec dec flys and cable crossovers the second and third most effective chest exercises.