The Achilles Tendon is the largest tendon in the human body and it stretches from your calf to your heel. Injuring your Achilles Tendon is pretty common. It is usually caused by not enough stretching and then suddenly engaging in very strenuous physical activity. Achilles Tendons can be strained, partially torn or ruptured completely. running, volleyball, gymnastics, basketball or tennis are a few of the sports where an Achilles Tendon injury is prone to happen, but it can also occur if your tendons are too tight or from wearing high heels.