There are several muscles in the front and back of the lower leg. The calf comprises two main muscles: the gastrocnemius and the soleus.
Calf injuries in runners! - The Physio Depot
Pain on inside of calves while running : r/trackandfield
Pain in Lower Leg Above Ankle When Running
Calf Muscle Tightness, Achilles Tendon Length and Lower Leg Injury — Mountain Peak Fitness
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Calf Muscles and Running: Injury and Care