The Achilles tendon connects two big muscles of the calf, the gastrocnemius and the soles, and attaches them into the back of your heel bone. These muscles are designed to forcefully pull your foot downward while allowing enough flexibility to bend your foot upward when running.
Running tends to cause these muscles and the Achilles tendon to tighten up. Without proper flexibility, the Achilles is forced to do much more work that it can handle.
This causes the tendon to become inlayed and it can tear or rupture if thou continue to work it. The Achilles, like all tendons, heals its injuries with scar tissue. This makes it weaker and more susceptible to further injury.
You must treat Achilles injuries quickly, before too much tearing or scarring occurs. Physiotherapy & Chiropractic Treatments include light stretches for the support muscles, Therapeutic Ultrasound, and the use of TENS machine to relieve pain.