extensor hallucis brevis muscle extensor hallucis brevis muscle the extensor hallucis brevis is a muscle on the top of the foot that helps to extend the big toe. extensor hallucis brevismuscles of the front of the leg. (ext. hallucis brevis colored in red.)animationdetailsorigincalcaneusinsertionproximal phalanx of digit 1 (hallux, or the great toe)arterydorsalis pedis arterynervedeep fibular nerveactionsextend halluxantagonistflexor hallucis brevis muscleidentifierslatinmusculus extensor hallucis brevista98a04.7.02.054ta22670fma51141anatomical terms of muscle structure the extensor hallucis brevis is essentially the medial part of the extensor digitorum brevis muscle. some anatomists have debated whether these two muscles are distinct entities. the extensor hallucis brevis arises from the calcaneus and inserts on the proximal phalanx of the digit 1 (the big toe). nerve supply nerve supplied by lateral terminal branch of deep peroneal nerve (deep fibular nerve) (proximal sciatic branches s1, s2). same innervation of extensor digitorum brevis function the extensor hallucis brevis helps to extend the big toe.