Soleus: The "weaker" of the calf muscles?

You'd be forgiven for thinking that the calf muscles, at the back of your leg below the knee, are comprised of 2 bell shaped muscles sitting next to each other. Actually, this is one muscle, the gastrocnemius. But this one muscle isn't the only muscle that forms the calf complex.

Underneath the gastrocnemius, is the soleus muscle.

You'd be forgiven again for thinking the soleus, being the thinner muscle sitting behind the big gastrocnemius muscle is weaker, but again, you'd be wrong!

Unlike the gastrocnemius which crosses the back of the knee, the soleus sits underneath the knee. Because of this, the soleus generates more power than it's bigger counterpart. This is because the soleus works when the knee is flexed (bent) and the gastrocnemius cannot work when this is the case.

To give you some figures from recent studies, the gastrocnemius provides 3 times your body weight in force during running, the soleus has to produce forces equivalent to 8 times your body weight, almost three times the force of the gastrocnemius. Therefore it is fair to say, this is a very strong muscle!

Then, this muscle must not be ignored in stretch and strengthening programs, particularly those involved in running! The runners stretch or heel drops and raises may not cut it when rehabilitating that painful, tired, achy calf complex. As this muscle needs this amount of force generation, it therefore needs equally as much strengthening work! An over active soleus can contribute to other foot and ankle muscle pains. Due to the anatomy of the calf complex, lying beneath the soleus is deeper, foot flexors.

Due to the tightly packed nature of the back of the leg, and the muscles being effectively in 3 layers, an over active calf can cause muscle pain to the tibialis posterior, flexor digitorum longus (toe benders) and flexor hallucis longus (big toe benders). These are the muscles required to plantar flex ( point the ankle down to the ground) and flex (bend downwards) our toes. Therefore, your toe and ankle pain, could be a result of an over-active soleus muscle. Don't forget this strong, little understated muscle!