The Achilles tendon connects the powerful muscles in the lower leg with the heel. Achilles strains are a common injury that can often become chronic and prevent any running. An Achilles strain is commonly an over-use injury that comes on gradually, although an increase in training load (e.g. hill or speed work) can suddenly make the problem worse. Also some running shoes, especially those with a high heel tab, can exacerbate the condition. Runners who over-pronate are particularly susceptible to Achilles problems. As well as being stiff and painful when stretched, the tendon may be sore to the touch and much thicker than the unaffected side. Initial treatment should be rest and application of ice to reduce pain and inflammation. It may be necessary to avoid weight bearing or impact exercise for a number of weeks to facilitate recovery and avoid re-occurrence of the injury. You should seek professional advice from a qualified physiotherapist who will provide treatment and massage to promote recovery. Rehabilitation exercises can be swimming and cycling where the Achilles is put under load, but there is little or no impact. Using a heel cup, wedge or Achilles support strap may prevent re-occurrence of the injury by reducing impact and protecting the tendon. You may wish to buy stability running shoes or orthotic insoles to reduce your tendency to over-pronate.