The Achilles (uh-KILL-eez) is the large tendon connecting the two major calf muscles to the back of your heel bone. If there's too much stress on the Achilles, the tendon can tighten and is forced to work too hard. When the tendon becomes inflamed, which is called tendonitis (tehn-dih-NYE-this), it can produce a covering of scar tissue. This scar tissue is less flexible than the tendon, and with continued stress it can tear (tehr) or rupture. There are several factors that contribute to Achilles tendinitis, including tight or fatigued calf muscles, excessive hill running, and inflexible running shoes. Runners who rotate their feet too far inward on impact are also susceptible to Achilles tendinitis. Initial symptoms of tendinitis can include dull or sharp pain anywhere along the back of the tendon, but usually close to your heel. Also, limited flexibility, redness or heat over the painful area, a cracking sound when you move your ankle, or a small lump located on your tendon can be symptoms of tendinitis. If you suffer from any of these problems, you should stop running or training, take aspirin or ibuprofen, and then ice the injured area for up to 20 minutes several times a day until the pain subsides. Once the lump is gone, stretch your calf muscles and don't start running until you can do toe raises without pain. Returning to physical activity should be a gradual process and not rushed. In case the injury doesn't respond to self-treatment within two weeks, you many want to see a physical therapist or doctor.