The calf ("Gastroc-soleus") is a pair of muscles at the rear of the lower leg, composed of:

• Gastrocnemius
  The larger of the muscles. Gives the familiar 'diamond' shape to a well-developed calf.
• Soleus
  Less visible than the Gastrocnemius, the Soleus adds with to the leg.

Many trainees find it difficult to grow their calves. This is usually because the calves are worked so frequently through daily activity (walking) that they require exceptionally intense training to promote growth.

Whilst the calves are trained indirectly through many compound movements, Calf isolation exercises nearly always involve the movement of "standing on your toes against resistance".

The Gastrocnemius is targeted through straight-legged exercises, whilst the Soleus can be targeted through bent-leg exercises.