that they assist with the function of both, making an injury to either muscle group extremely disruptive to running. Both can be strained (or pulled) if they are overextended to the point that they rip slightly. A complete tear of the muscle is called a rupture
fascia, the tendon or its surrounding sheath can become inflamed when overworked, causing Achilles tendinitis. "This is often an overuse injury," says Weldon. "The Achilles tendon is overstretched because of the tilting of the heel during extended
