The Soleus: An Unsung Hero in Runners

There are over 600 muscles found in a human body. This number makes it quite difficult to give every muscle the attention that it deserves. Based on my clinical experience, there are certain muscles that I have found to be the most overlooked, underappreciated, and neglected, leading to muscle imbalances throughout the body with subsequent injury. This blog series will be dedicated to educating our readers about specific undervalued muscles that are extremely pertinent to optimal performance and injury prevention in endurance athletes. The first muscle that I want to feature in this series of unfortunately underrated muscles is the soleus muscle.

First, let’s start with the anatomy of the soleus muscle. The soleus muscle is one of the main muscles that make up the calf complex. Most people are familiar with their “calf muscle”, however, many people do not realize that it is actually composed of several different muscles. The two main muscles that make up our calf complex include the gastrocnemius and the soleus. These muscles are stacked on top of one another. The gastrocnemius is the most superficial and the large, broad, and flat soleus muscle is located just underneath. The gastrocnemius muscle crosses the back of the knee joint, and the soleus does not. They both come together to form the Achilles tendon which attaches at the heel, but is continuous with the fascia throughout the bottom of the foot, our plantar fascia.

What does the soleus do?

The gastrocnemius and soleus work together to perform plantar flexion (aka pushing the foot downward toward the ground in a heel lifting motion), however, these muscles also work heavily in isolation. The gastrocnemius is responsible for plantar flexion with the knee straight, as well as assisting with knee flexion or bending the knee. The soleus is responsible for plantar flexion of the foot with the knee bent, leading to propulsion and forward acceleration of our trunk during activities such as walking and running. The soleus also helps stabilize and decelerate the tibia, or lower leg, through the stance phase of gait [6]. The soleus muscle plays a major role in producing propulsive force during endurance running.

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