Please do a test before reading this article: squat to the bottom (back of thighs in contact with back of calves) with both bare feet together (not only heels together, but also the inside of the feet). Those who cannot finish or need to lift their heels are considered positive. Those who are positive may have functional Achilles tendon contracture. Of course, obesity can also affect the results and requires further examination by a foot and ankle doctor. There are many causes of functional Achilles tendon contracture, including acquired and congenital causes, including trauma, long-term braking, neuromuscular disease, and sports injuries. Congenital causes include trauma, long-term braking, neuromuscular diseases, sports injuries, etc. Congenital causes are called “revertive phenomenon” (mammals are all toes-on-the-ground, and can’t flatten their feet like human beings). Due to Achilles tendon contracture, dorsiflexion of the foot is limited, the compliance of the foot is reduced, the pressure of the forefoot increases when walking, and the foot pads appear on the bottom of the foot, which can be complicated by heel pain, Achilles tendonitis, plantar pain, metatarsal tendonitis, and metatarsal head necrosis in the long term. Regular Achilles tendon pulling exercises under the guidance of a foot and ankle doctor (see “Metatarsal Tendonitis”), choosing the right shoes and customizing the insoles can reduce the chances of complications.