Stand on the hack machine platform with your back flat against the rest and the shoulder pads on top of your shoulders.
Adjust your feet so that only the balls of your feet are on the platform. The heels and arches of your feet should be extending off the platform.
Unlatch the hack machine from the rail.
Keeping your knees almost fully extended, exhale as you push the hack machine up and away from the platform by plantarflexing your ankles.
Hold for a count of two.
Inhale as you slowly lower the hack machine back down to the starting position by dorsiflexing your ankles until you feel a mild stretch in your calves.
Repeat for the desired number of repetitions.
After you have finished, latch the hack machine back onto the rail.
Comments and tips
Make sure that your back is flat against the rest, your hips are extended and your knees are almost fully extended throughout the exercise.
If the platform of the hack machine does not have an open lower end, see if it can accommodate a calf block.
While plantar flexion exercises activate both the gastrocnemius and soleus, one will be emphasized over the other depending on whether or not the knee is flexed. Since the knee is extended in this exercise, the gastrocnemius is emphasized over the soleus. The soleus is only emphasized in exercises in which the knee is flexed because the gastrocnemius muscle becomes loose in such a position.
If you turn your toes outward, the inner (medial) head of your gastrocnemius will be emphasized. On the other hand, if your turn your toes inward or keep them pointing forward, both the inner and outer (lateral) heads of your gastrocnemius will be activated approximately equally.