What is the primary action of the soleus muscle?

The primary action of the soleus muscle is indeed plantarflexion of the ankle. This muscle is located in the posterior compartment of the leg, beneath the gastrocnemius, and it plays a crucial role in various activities such as walking, running, and jumping. When the soleus contracts, it helps to point the toes downward and facilitates movements that require pushing off the ground, such as during the propulsion phase of walking or running.

Its primary function is especially significant when the knee is flexed because the soleus remains active during activities such as standing on tiptoes or performing calf raises. Unlike the gastrocnemius, which also assists with knee flexion, the soleus is primarily focused on maintaining posture and stabilizing the ankle joint during movement. This makes the understanding of its function essential for those studying anatomy, physical therapy, and various fitness disciplines.