The shoulders ("Deltoid") are a muscle group with 3 distinct parts, or 'heads' - Anterior (front), Medial (side) and Posterior (rear).

To fully train the deltoid, each head must be targeted:

• Anterior (front)
  This is used in all pressing exercises, such as the Bench Press, Military Press, etc. However, it can be trained in isolation with Front Raise movements.
• Medial (side)
  The medial deltoid can be trained by Side Raise movements. The medial deltoid is involved to a lesser extent in pressing movements.
• Posterior (rear)
  The posteroir deltoid is best trained with Rear Flye movements (bent-over, or chest-supported). It is also involved, to a lesser extent, in exercises such as the bent-over dumbell row, and cable row.