The incline bench press engages the pectoralis major and other muscle groups.
The pectorals are the muscles that, as a group, comprise the chest area. Most chest exercises focus on the pectoralis major, which is the large band of muscle forming the center of the pectorals. To target and isolate other muscles in the chest area, you need to incorporate specific exercises into your strength-training regimen. For example, the pectoralis minor is a difficult muscle to engage, and exercises like the incline bench press don't incorporate it. But there are a couple of exercises that will.
The pectoralis minor is a small strip of muscle that extends vertically along the outer edge of the chest, from the arm pit to the top of the abdomen. The muscle supplies assistance and stabilization for the rotation and abduction of the shoulders. The muscle is difficult to work out, as many common chest and shoulder exercises don't directly engage it. Due to its vertical alignment within the body, the most effective way to target the pectoralis minor is from the upright position.
Incline Bench Press
The incline bench press targets the pectoralis major, with special focus on the clavicular and sternal heads of the muscle group. The incline press also incorporates the deltoids, triceps and biceps. The exercise can be performed with a weighted barbell, independent dumbbells, kettlebells or cables attached to a stacked weight machine. The angle of motion as you sit at about 45 degrees doesn't place any stress from the weight on the pectoralis minor in either the lift phase or the control phase of the press.
Two effective chest exercises will directly engage the pectoralis minor -- the chest dip and the standing cable fly. The chest dip is a simple body-weight exercise that uses a dip rack that orients you directly perpendicular to the ground. The stress of your body's weight engages the muscle both during the downward control motion and the upward lift motion. The standing chest fly using cables engages the pectoralis minor in a similar way. Pulling the cables forward and slightly down toward the ground, using the pulleys and stacked weight for resistance, will engage those muscles along with the pectoralis major, the deltoids and the latissimus dorsi.
Performing too many chest-focused exercises intending to engage every muscle in the pectorals can lead to injury and to diminished performance over time from overtraining. In many cases, one or two sets of chest dips in conjunction with other pectoral exercises will be sufficient to develop functional chest strength. Remember, it will be difficult to see any noticeable definition in the pectoralis minor as you develop strength in the chest, because it's not a muscle that lends itself to mass development. Any exercises used to target the pectoralis minor specifically should only be supplementary in nature.