Final answer:
The gastrocnemius and soleus muscles act in synergy as prime movers for planter flexion in the leg.
Step-by-step explanation:
Two muscles that act in synergy as prime movers for plantar flexion are the gastrocnemius and the soleus. These muscles are located in the posterior compartment of the leg and primarily function to raise the heel and push off the ground during activities like walking, running, and jumping.
The gastrocnemius is the larger muscle that forms the bulk of the calf, while the soleus lies deeper and is responsible for maintaining posture.