The Achilles tendon connects the calf muscles (gastrocnemius, soleus) to the heel bone (calcaneus). It is the largest tendon in the body and allows a person to walk, run, jump, stand on toes, and go up and down stairs. During running, it is subjected to increased loads of up to 12 times body weight.
Achilles tendon injuries are some of the most common running injuries sustained and have been deemed an overuse injury. However, more up to date research indicates that not only can this type of injury be attributed to overuse but it can also be a consequence of degenerative changes (wear & tear) present in the tendon.