It may seem to you that it is harder to build the inner chest as opposed to the outer chest. There are three basic reasons why:
Not using proper form and technique
Not understanding arc movements.
The truth is this: In order to most effectively build the inner chest, you must remember that it’s not about the extension of the arms, but it’s about the rotation of the shoulder. For you to acquire a peak contraction in the chest, it requires the shoulder to completely rotate forward as you are contracting with resistance. Unfortunately, because of the inherent constraints of most chest exercises, building a great chest becomes more difficult. Quite frankly, most exercise equipment is inadequate when it comes to maximizing the development of the chest. In fact, I had to design my own piece of exercise equipment — the Iron Chest Master — in order to find an adequate remedy for this problem.
The Iron Chest Master allows its user to move in the same arc formation as a bird in flight, mimicking the arc movement and developing the chest, in the same manner, using the downward pressure of gravity during the pushup phase, along with lateral resistance from resistance bands, creating a peak contraction and complete development of the inner chest.
Let me explain some of the limitations of a few of the most popular chest builders:
The pushup is a convenient exercise that can be done just about anywhere without a person ever having to go to the gym. There are a right way and a wrong way to do a pushup, and neither of these ways will adequately train your inner chest. The most effective way to work your chest while doing a pushup is to make sure you assume a power position, meaning that your hands are far enough apart that your triceps and your forearms reach a 90-degree angle, and your wrists, elbows, and shoulders are on the same plane as your chest proceeds down toward the ground.
Dumbbell Press and Bench Press:
The dumbbell press is better than the barbell bench press because the movement can be adapted to the body, and the hands and arms can move independently from one another. However, dumbbells still can’t create any lateral resistance that directly affects the inside of the chest because the resistance always comes in the form of gravity, from the floor to the ceiling. Both pushups and bench presses will never allow you to achieve a peak contraction because they lack a full range of motion and lateral resistance.
One of the fundamental problems with a chest fly is that the motion involves the use of the bicep. The further your hands slide away from your body, the more the biceps are involved in stabilizing the weight. The bicep is a much smaller and weaker muscle group than the chest, so the bicep limits the amount of weight you can use. Also, there is no direct lateral resistance. This is yet another case where resistance in the motion is delivered by gravity, and it is generated vertically from the floor to the ceiling. At no point does the manipulation of the hands compensate for this.
Cable crossovers allow you to build the middle of your chest, but once again, there’s an obvious limitation when it comes to training the inner part of the chest: All of the resistance comes from behind you, and there is no way to change its direction. Cable crossovers will permit you to stretch the shoulders back to open your chest wide, and then you can drive both the shoulders and arms forward, squeezing in the center. This gives you one of the best center-chest contractions available through normal means, but it still doesn’t provide you with any focused, lateral resistance. Moreover, this movement completely lacks the power position, which is your body’s strongest position.