Tendon the Achilles tendon stretches as the ankle joint dorsiflexes. During the last portion of the stride, as the foot plantar-flexes (pointing the toes down), the stored elastic energy is released. Furthermore, because the tendon stretches, the muscle is able to function with less or even no change in length, allowing the muscle to generate greater force. The mechanical properties of the tendon are dependent on the collagen fiber diameter and orientation. The collagen fibrils are parallel to each other and closely packed, but show a wave-like appearance due to planar undulations, or crimps, on a scale of several micrometers. In
Achilles tendon expression "Achilles' heel") and he was eventually killed by a poison dart to the heel. The name thus also refers to the particularly disabling and painful effect of an injury to this tendon. The first closed rupture was described by Ambroise Pare in the sixteenth century. The Achilles tendon is also known as the "tendo calcaneus" (). Because eponyms (names relating to people) have no relationship to the subject matter, most anatomical eponyms also have scientifically descriptive terms. The term calcaneal comes from the Latin "calcaneum", meaning heel. Achilles tendon The Achilles tendon or heel cord, also known as the