Soleus

A powerful muscle located in the lower leg, playing a crucial role in standing and walking.

The soleus is one of the major muscles in the calf, situated beneath the gastrocnemius muscle. It originates from the upper part of the fibula and the tibia and inserts into the Achilles tendon, which connects to the heel bone. This muscle is uniquely adapted for endurance activities due to its high concentration of slow-twitch muscle fibers.

Terminologia Anatomica

musculus soleus

System

Muscular system

Function

The soleus muscle is primarily responsible for plantar flexion, which involves pointing the toes downward. It plays an essential role in various activities, including walking, running, and maintaining balance while standing. Unlike the gastrocnemius, which is more involved in explosive movements and bending the knee, the soleus works continually during prolonged activities, thereby stabilizing the body when standing upright and providing propulsion during the gait cycle. As we push off from the ground with each step, the soleus contracts to help propel the body forward, making it pivotal for activities that involve continuous muscle contraction, such as walking or standing for extended periods.

Location

Located in the posterior compartment of the leg, the soleus muscle lies deep to the gastrocnemius muscle, which is the more prominent calf muscle visible from the surface. It extends from just below the knee to the heel, covering the lower portion of the tibia and fibula. The muscle's shape is often described as flat and broad, resembling a fish, which is where the name 'soleus' is derived from. It merges into the Achilles tendon at its distal end before attaching to the calcaneus (heel bone), ensuring effective force transfer to facilitate movement.

Did You Know?

The soleus is sometimes referred to as the 'second heart' because of its crucial role in helping to pump blood back to the heart from the lower extremities.
This muscle has a rich blood supply and is highly vascularized, which enables it to sustain long periods of activity without fatigue.
In individuals who are sedentary or have a deconditioned lifestyle, the soleus can become weak, leading to balance issues and increased risk of falls.