Deltoid Muscles: Function, Anatomy & Shoulder Movement

Deltoids are the muscles that give shape to your shoulder. They play an important role in moving your arm in different directions — flexing, extending, rotating, and abducting (moving away from your body).

The deltoids are made up of three parts or heads: anterior (front), lateral (side), and posterior (back of your shoulder). Each head is responsible for a specific movement of your shoulder:

- Anterior deltoid: flexes your shoulder

- Lateral deltoid: abducts your shoulder

- Posterior deltoid: extends and rotates your shoulder

Deltoids are used during many everyday activities, from lifting objects and throwing to climbing stairs and reaching overhead. They are also important muscles used in various sports and exercises, such as swimming and weightlifting.