Building evenly shaped chest muscles is not as simple as lifting heavy weights frequently on a bench press. You must understand the difference between your pectoralis major and pectoralis minor muscles, and how different exercises affect these muscle groups. Developing this understanding will allow you to build your pecs fully through targeted training.
The pectoralis major is the large muscle that you mostly sees in the upper and middle portion of your chest. This muscle originates at your breast bone and connects to your humerus near your shoulder joint. It fans down your chest toward your rib cage. The pectoralis minor is underneath the major and originates at your ribs. It connects high on your chest at the scapula. The pectoralis minor helps to give definition to the lower portion of your pectoralis major to form what are commonly seen as the lower pec muscles.
The common flat bench press does not effectively develop your upper or lower pecs. This exercise mostly works the middle of your pectoral muscles, leaving you with a strong but flat chest. To build the upper and lower portions of your pectorals, including your pectoralis minor, you must perform sets of inclined and declined bench press. Variations of these exercises can also be performed with push-ups, dips and dumbbells.
Upper pecs play a much greater role in your overall chest development than your lower pecs do. Performing the inclined bench press first will bring the most shape to your pec muscles overall. This is because you are working the origin point of your pectoralis major at the sternum. The origin point is where the muscle attaches to the sternum. Working this area first produces more muscle growth at the origin point than if you fatigued the muscles with the flat bench press first.
One trait that the upper and lower portion of your pecs share is that they benefit the most from an exercise when they are fully contracted. Fitness guru and author Rusty Moore advises that for each repetition you perform, you should practice contracting the appropriate portion of your chest as hard as you can. This will exhaust your muscles quicker, giving you more definition and strength throughout your chest.