Your gastrocnemius and soleus, the two major muscles of your calf, power every walking and running step you take. Although having the strength and endurance to provide that power is important, calf flexibility also matters. If your calf muscles aren't flexible, you may strain or even rupture your Achilles tendon, or one of the muscles themselves, during your workout.
Primary Function
The primary function of both your gastrocnemius and soleus is plantarflexion of the foot, or in other words, pointing your toes. You stretch a muscle by performing the opposite motion it normally performs; to stretch your gastrocnemius and soleus, you must dorsiflex your feet, or bring the tops of your feet closer to your shins.
An Exception
The gastrocnemius performs more than one joint motion. Unlike the soleus, which only crosses the ankle joint, the gastrocnemius also crosses the back of your knee and thus assists your hamstrings with knee flexion. If you dorsiflex your foot with the leg straight at the knee, you'll stretch your gastrocnemius and possibly your soleus as well, although the gastrocnemius flexibility typically limits this stretch before you feel it in the soleus. To specifically target the soleus, dorsiflex your feet with your knees bent.
Standing Calf Stretch
You can adapt most calf stretches to target both muscles in turn. For a basic standing calf stretch, stand close to a wall you can lean on for balance. Step one leg back into a lunge and bend your front knee, but keep the back leg straight. Press your back heel toward the floor until you feel a stretch in your calf; because your leg is straight, you're stretching your gastrocnemius. To target your soleus, scoot your back leg forward until you can rest your heel on the floor. Bend your back knee slightly and sink into the stretch until you feel mild tension in your calf again; this is your soleus.
Seated Calf Stretch
You can also stretch your calves while seated. If you're not very flexible in the hamstrings and lower back, you may need a towel or strap to assist with this stretch. Sit down on a bench and let one leg hang off the side of the bench; extend the other leg straight in front of you. Lean forward and gently pull the toes of that extended leg back toward you until you feel tension in your calf. If you can't reach your toes, wrap the towel or strap around the ball of your foot and pull back gently. Bend your knee to switch the stretch from your gastrocnemius to your soleus.
