A tendon is a band of tissue that connects muscle to bone The Achilles tendon connects your calf muscles to your heel  allowing you to walk  run and jump Achilles tendinopathy  strain of the Achilles tendon  is a common injury that may affect runners  or people with overpronated (flat) feet or those with high arches or tight calf muscles as well as those who wear runners that are not an appropriate biomechanical fit for them