The Achilles tendon is the largest and strongest tendon in the body. When the calf muscles flex, the Achilles tendon pulls on the heel. This movement allows us to stand on our toes when walking, running, or jumping. Despite its strength, the Achilles tendon is also vulnerable to injury, due to its limited blood supply and the high tensions placed on it.
Frequent activity (running or walking) can gradually inflame the end of the Achilles tendon, causing pain and stiffness at the back of the heel. Rest, ice, and stretching may speed healing, which can take weeks.