The primary function of the calf is to extend the ankle. It is made up mainly of the gastrocnemius and the soleus muscles, which merge and attach to the heel, forming the Achilles tendon. The gastrocnemius starts above the knee and extends the ankle when your leg is straight. The soleus starts below the knee and extends the ankle when your leg is bent. According to veteran bodybuilder Tim Wescott, you must work the calf with straight and bent legs, and with a variety of techniques, to build muscle.
Standing Calf Raises
Adjust the shoulder pads of the calf raise machine to suit your height.
Step up onto the block on the balls of your feet, with your shoulders under the pads and feet pointing forward.
Stand erect, pushing the pads up with your shoulders. Keep a slight bend in your knees.
Extend your ankles, pushing up as high as you can on the balls of your feet, keeping your legs and body straight.
Pause, and return past your starting position so you feel a stretch in the belly of the calf.
Seated Calf Raises
Sit on the machine with feet pointing forward and the balls of your feet on the platform.
Adjust the thigh pad so it rests just above your knee.
Release the safety bar by pushing up slightly with your heels.
Allow your heels to drop slowly until you feel a full stretch in your lower calf.
Pause, and extend the ankles as high as possible.
Hold briefly at your full extension, and return to the bottom of the movement.