Final answer:
The gastrocnemius muscle causes plantar flexion of the foot, which is the movement lifting the heel off the ground. It is part of the posterior compartment of the leg and inserts onto the Achilles tendon, playing a vital role in walking and running.
Step-by-step explanation:
The muscle that causes plantar flexion of the foot is the gastrocnemius. Plantar flexion is the movement at the ankle that involves lifting the heel off the ground, akin to standing on tiptoes. The gastrocnemius is the most superficial and visible muscle in the calf, part of the posterior compartment of the leg, which all insert onto the strong calcaneal tendon (Achilles tendon). This action is crucial for activities like walking, running, and jumping.
Other muscles like the soleus, plantaris, and the two fibularis muscles namely, fibularis longus and fibularis brevis, also contribute to plantar flexion, but it is the gastrocnemius that is principally responsible for this movement. The gastrocnemius works in conjunction with these muscles, providing the strength and movement necessary for plantar flexion. While the iliopsoas is involved in hip flexion, the vastus intermedius in knee extension, and the fibularis tertius helps with foot eversion, it is the gastrocnemius that is the prime mover in plantar flexion of the foot.