When most people think about calf training, they think about the gastrocnemius : the big calf muscle you see. But the soleus , the deeper calf muscle, is actually the workhorse for walking, running, hiking, stairs, and especially downhill movement . If the gastrocnemius helps push you forward , the soleus helps slow you down . And in real life (and in sport) deceleration is where most injuries occur. Why the Soleus Matters So Much The soleus plays a major role in: Walking and