Deltoid Training

The deltoid muscle has three sections, the front head, the side head and the rear head. These heads have different actions and so need different strength training exercises to completely train the whole of the muscle.

* The front deltoid is used in all pressing movements, such as the bench press, and can be trained adequately without any isolation movements. However for isolation front dumbbell raises are the most commonly used.

* The middle head of the deltoid is the main abductor at the gleno-humeral joint (shoulder) and is commonly trained using side lateral raises (also known as the shoulder fly. The middle head also benefits from overhead pressing movements.

* The rear head of the deltoid is best trained with bent-over dumbbell laterals (an inverted fly)

Wikipedia