Shoulder Anatomy 101
Before you can properly develop a set of strong shoulders, you first have to understand the underlying muscle structure. By knowing shoulder anatomy, you can target the shoulder muscles with specific exercises that will strengthen all of them and keep your form in balance.
Also, the shoulder contains a delicate system of small muscles which are built around a ball and socket joint and can easily be overworked and sustain injury. Since your shoulder provides an incredible range of motion, it’s important to know how your shoulder moves and what muscles govern those movements so you can reduce shoulder injury during workouts.
The deltoid muscles cover the outer surface of the shoulder joint and consist of three separate layers:
Anterior Deltoid – The anterior deltoid muscle is located at the front of the shoulder and is responsible for rotating the arm inward. The anterior deltoid is often over-developed because it is engaged through a variety of arm and chest exercises. If you do not develop the other shoulder muscles when building the anterior deltoids, you may experience posture problems and muscular imbalance.
Medial Deltoid – This shoulder muscle is located on the outside of the shoulder head. The medial deltoid flexes to move the arm away from the body. By developing the medial deltoids through isolated shoulder abduction exercises like lateral dumbbell raises, you round out the shoulders and increase the width of the upper V-shape.
Posterior Deltoid – The muscle responsible for rotating and extending the arm outward is the posterior deltoid. It is located at the back of the shoulder and is strengthened through such exercises as pull ups, chin ups, reverse flyes, rows and other back building exercises.