According to "Strength Training Anatomy," an incline bench press is a chest press performed on an incline bench with an angle of 45 to 60 degrees. This angle reduces stress on the lower portions of the pectoral muscles and places it on the upper portion and the shoulders. Because the lower portion of the pectoral muscle is the strongest, most people aren't able to incline press as much weight as they can flat press.
Pectoralis Major
The pectoralis major--commonly known as the pecs--are the primary movers in the incline bench press. The lowest portions of the pectorals are dominant in bringing the arms together over the stomach, the middle over the sternum, and the upper over the clavicles. Because of this, it's the upper pectorals that are used most in the incline bench press. The upper pectorals connect to the clavicle, and so are called the clavicular head of the pectoralis major. In well-defined pectorals, this clavicular head is clearly separate. Because the development of the upper pectorals tends to lag behind the lower portions, in "The New Encyclopedia of Modern Bodybuilding" eight-time Mr. Olympia Arnold Schwarzenegger advises doing incline bench presses regularly.
Anterior Deltoid
The deltoid is composed of three heads: anterior, medial and posterior. The anterior head is the front-most, and attaches to the clavicle directly outside the clavicular head of the pectoral. The anterior deltoid head moves the arms forward and up, and so is heavily utilized during the incline bench press. Because the anterior deltoid is involved in most pressing exercises, it's common for it to be the most developed of the three deltoid heads.
Triceps
The triceps are involved in all pressing exercises, as they are responsible for straightening the arms at the elbows. Because the incline bench press involves a larger range of motion than the flat bench press, the triceps are heavily involved. The angle that the arms form at the bottom of an incline bench press put the triceps in a less-advantageous position than in a flat bench, requiring more triceps strength. The incline bench especially emphasizes the long head and the medial head of the triceps.
Serratus Anterior
The scapula also go through an extended range of motion during the incline bench press, due to the elbows passing further behind the torso. This means that they are retracted by the pressure, and then must be protracted by muscle. That muscle is the serratus anterior. The back side of the serratus anterior attach to the scapula, while the front attach to the upper nine ribs just inside the latissimus dorsi and under the pectorals.
References
- "Strength Training Anatomy 3rd Ed."; Frederic Delavier; 2010
- "The New Encyclopedia of Modern Bodybuilding"; Arnold Schwarzenegger; 1998
Member Comments