Increasing the flexibility of the calf muscles increases the range of dorsi flexion of the ankle. This means the toes of the foot can be brought closer to the shin bone. At the end range of dorsi flexion there is a flattening of the arch of the foot which further increases the range of motion of the ankle. Increasing the range of dorsi flexion of the ankle has a number of functional benefits as it produces a delayed flattening of the arch of the foot. This has particular beneficial in preventing internal rotation of the knees and hips during walking, running and squatting. If you attempt to perform an overhead squat you'll become very aware of how a limited range of ankle dorsi flexion effects the foot and knees.
The Gastrocnemius is the outer most calf muscle which is visible to the eye. It is less likely that a tight gastrocnemius will limit ankle range of motion as much as a tight soleus. This is due to the gastroc crossing both the knee and the ankle joint. Excessive lengthening of the gastroc may increase the load on the soleus similarly a tight gastroc will increase its activity relative to the soleus. If you find you tear the outer most calf muscle then focus your stretching hear. If tearing the deaper soleus muscle is the concern then focus on stretching the soleus (see below)
In order to stretch the gastrocnemius the knee must be straight or extended. If the knee is bent the soleus muscle will be stretched as opposed to the gastroc.
Place your heel as close to a post or wall as possible. Whilst keeping your knee straight push your body weight forward. You may need to pull on the post in order to gain a sufficient stretch
Hold yourself in a push up position with your hips high. Take one foot off the ground and try and push the heel of the other foot onto the ground. If you can't reach the ground you can make the stretch easier by walking your foot closer to your hands. Similarly taking the foot back will increase the difficulty of the stretch
The soleus is the deeper of the two calf muscles. It is visible on the medial side of the lower leg before proceeding out of sight behind the gastroc
The gastroc is stretched when the toes are pulled towards the shin when the knee is straight, bending the knee releases the tension on the gastroc enabling the toes to be pulled closer to the shin. As a result the soleus has more of an effect on ankle dorsi flexion or ankle range of motion in functional movements. During a squat or the toe off stage in running the knee is bent enabling a greater range of motion as the ankle. As a result the soleus comes into tension. For this reason its thought that many of the calf strains that occur during running have there origin in the soleus as opposed to the gastrocnemius
Kneel in a lunge positions. Whilst keeping your front heel on the ground, push your weight forward over your toes. You should feel a stretch in the soleus on the front leg. Try to maintain the height of the arch in the stretching leg
Whilst keeping your back heel on the ground, bend the knee and push your weight forward over the toes. Keep your back knee in a neutral position over the toes and maintain the arch of the foot. You should feel the stretch in the soleus of the back leg