The Achilles connects the heel to the calf. The Achilles tendon is the thickest and strongest tendon in the body. Walking, running and jumping all subject the Achilles tendon to the persons entire body weight. If impact is involved (as in jumping/running) it can be 3-20 times the personas body weight!
Overuse, poor posture, accidents and improper footwear all can result in injuring the Achilles. The most common injuries are Achilles tendonitis and Achilles tendon rupture.
Achilles tendonitis is an inflammation of the Achilles tendon. This comes on slowly and does not go away until you do something about it. It is most painful when you start doing exercise and it goes away after you have been exercising for a while. It is extremely sore to squeeze.
Achilles tendon rupture is a tear of the tendon. This comes on very quickly and is unbearable pain. There may be a snap noise and you will be unable to walk. It is common in a sudden event such as pushing off on the toes.
To treat these couple of injuries, they need rest, ice and a physio. The rupture will need complete immobilization, and sometimes surgery.
Once you are pain free you should stretch and strengthen the calf muscles. Stretch the gastrocnemius and soleus out 3 times a day. When strengthening use calf raises and focus on the downward phase (eccentric contraction) - aim to count to 5 on the way down... nice and slow!!
Correct shoes can be the key to preventing and recovering from Achilles tendon injuries. Some people may benefit from orthotics which are inserts which you slot into your shoes, that alter your amount of cushioning and arch height.