Which muscle is primarily responsible for the action of extending the great toe?

The muscle that plays the primary role in extending the great toe is the Extensor hallucis longus. This muscle originates from the anterior surface of the fibula and the interosseous membrane, and it travels down the leg, eventually inserting onto the distal phalanx of the great toe. When contracted, the Extensor hallucis longus performs the action of extending the great toe at the metatarsophalangeal and interphalangeal joints, enabling functions such as toe-off during walking and running.

The Flexor hallucis longus, while important for flexing the great toe, is not responsible for extension and thus will not assist in this specific muscular action. The Tibialis posterior primarily functions to plantarflex and invert the foot, but it does not extend the great toe. Similarly, the Gastrocnemius is primarily a plantarflexor of the ankle and does not have any significant action on the great toe. Therefore, the Extensor hallucis longus is the correct muscle associated with the extension of the great toe.