The calves are a group of muscles that are located farther down the back of the leg running from the backside of the knee to the Achilles tendon. The two muscles that make up the calves are the gastrocnemius and the soleus. The primary function of these muscles is to extend your foot at the ankle and flex your toes, which helps you jump, walk, run and pedal.
Optimizing your calf muscles when training in the gym requires a careful understanding of the anatomy and characteristics of each muscle and their specific functions. Since the two main muscles of the calves consist of the gastrocnemius muscle and the soleus muscle, we will go into depth about these key muscles and explain why they play a major role in the functioning of the lower leg.
Exercise Guides For Your Calves!
Physiology of The Gastrocnemius Muscle
The gastrocnemius is also referred to as the “gastroc”. This muscle is the larger and more prominent of the two calf muscles. It is present in the superficial posterior of the leg, meaning it is present over the soleus muscle and to the back of the knee. It is made up of fast twitch muscle fibers, and therefore, responds to low reps and heavier weight when training with weights.
The gastrocnemius muscle possesses both a lateral and a medial head with the medial head being the longer one. Both heads originate from the distal posterior femur from the lateral and medial side, respectively. They are then connected by way of insertion on the Achilles tendon, which in turn, attaches itself to the heel bone.
The lateral and medial heads’ fibers mirror their movements while traveling oblique to the tendon separating them. They are bipennate, meaning their range of motion is relatively restricted even as they can transmit more power; as they are arranged obliquely to the tendon attaching to them.
Functions of The Gastrocnemius Muscle
The gastrocnemius muscle is the most active when the knee is straight. Then it is the prime mover in plantar flexion of the ankle (moving the ankle down so that it is somewhat perpendicular to the knee) along with help from the soleus muscle. Therefore, it is critical in helping produce the normal range of motion of the ankle and the foot. When the knee is bent, the gastrocnemius becomes progressively less engaged and hands over the load to the soleus.
Physiology of The Soleus Muscle
This muscle is the smaller of the two calf muscles and yet equally as important in training. The soleus is almost under or behind the gastrocnemius muscle, and is therefore, almost invisible in the exterior shape of the calf. However, when exercised enough, this muscle can show clear definition and add to the shape and symmetry of the calf.
The soleus is also present in the superficial posterior of the leg, meaning it is to the back of the knee. In contrast to the gastrocnemius, the soleus muscle has mostly slow twitch fibers, and therefore, responds best to higher reps and lower weight when training.
The soleus has only a single head and also shares a common insertion point with the gastrocnemius muscle. This is why both of them combined are called the three-headed muscle or “triceps surae” of the calves muscle group even though they are different muscles.
The soleus muscle has multiple originating points inside the tibia and in and around the back of the fibula. It also finally inserts to the Achilles tendon. Its fibers run between multiple septa, also forming an oblique but multipennate architecture.
Functions of The Soleus Muscle
The soleus is the prime mover in ankle plantar flexion when the knee is bent. It is also mainly responsible for stabilizing the ankle and helping us stand straight. Interestingly, it is also called the “second heart” because it is one of the most important muscles that helps pump blood back to the heart.