The bench press is a compound movement, involving multiple joints and engaging several muscle groups simultaneously. The anterior deltoid, or the front portion of the shoulder muscle, plays a role in this movement, which involves pushing a weight away from the chest. Many lifters question whether this shoulder muscle is sufficiently engaged to count as a dedicated deltoid exercise.
Primary Muscle Activation During the Bench Press
The flat barbell bench press relies heavily on two large muscle groups to generate the pushing force. The main muscle performing the work, known as the prime mover, is the Pectoralis Major, or the chest muscle. This muscle is responsible for horizontal adduction, the action of bringing the upper arm across the body’s midline during the upward press. The second major muscle group involved is the Triceps Brachii, located on the back of the upper arm. The triceps are responsible for elbow extension, providing the necessary force to straighten the arms and complete the lockout portion of the lift.
The Specific Role of the Anterior Deltoid
The anterior deltoid is involved in the bench press, but it functions in a supporting capacity rather than as the primary force generator. It is categorized as a synergist muscle, meaning it assists the prime movers to complete the action, and also acts as a stabilizer for the shoulder joint under load. Its mechanical function is to contribute to shoulder flexion, particularly during the initial phase of the press as the bar leaves the chest.
Electromyography (EMG) studies, which measure muscle electrical activity, confirm significant activation in the anterior deltoid during the flat bench press. While some research suggests its activation can be similar to the pectoralis major at a flat angle, it is generally considered secondary to the combined effort of the chest and triceps. The deltoid helps initiate the movement and control the shoulder joint’s position, ensuring the force is directed correctly. This assistance is important for a smooth and stable press, especially when lifting heavier weights. The muscle is also constantly engaged to prevent the shoulder from rolling forward under the bar’s weight, which is part of maintaining joint integrity.
Modifying Bench Press Technique to Adjust Deltoid Involvement
Lifters can manipulate their bench press technique to strategically alter the degree of anterior deltoid recruitment.
Increasing Deltoid Activation
The most effective way to increase its involvement is by performing the incline bench press. Raising the bench to an angle, typically between 30 and 45 degrees, shifts the movement pattern to prioritize shoulder flexion, which is a primary function of the anterior deltoid. Studies show that increasing the bench angle beyond 45 degrees causes a significantly higher activation of the anterior deltoid, often at the expense of the lower chest muscles.
Decreasing Deltoid Activation
Conversely, techniques can be used to decrease the reliance on the anterior deltoid, focusing more on the pectorals and triceps. Utilizing a wider grip, for example, shortens the range of motion and emphasizes the horizontal adduction function of the chest muscles. A wider grip may also reduce the degree of shoulder flexion required to complete the lift, de-emphasizing the anterior deltoid’s role in initiating the press.
Another common technique is to tuck the elbows closer to the body during the descent and ascent. This places a greater emphasis on the triceps and chest by reducing the amount of shoulder rotation, thereby minimizing the mechanical advantage of the anterior deltoid.