Understand the Anatomy of the Calf Muscle: A Guide to Building Stronger Muscles The calf muscle is made up of two main muscles: the gastrocnemius and the soleus. These muscles are responsible for ankle movement, which is essential for walking, running, and jumping. Therefore, keeping these muscles strong and flexible is important to prevent injuries and improve athletic performance. In order to properly strengthen and stretch your calf muscles, it’s important to understand the anatomy of the muscle.