AOKK Isshin ryu: Back Kick [Ushiro-geri]

The best way to describe this kick is that it is the same motion that a mule uses when it kicks. It is sometimes referred to as a Mule kick. This kick is most effective against a surprise attack from behind or if your back has been turned in a fight. The karateka must look over the shoulder bring the knee forward and thrust the kick backwards. The foot is pointed downward, and striking part of the foot is the heel. 

This kick is also affective if the attacker has rushed you and you sidestep the attack. As the aggressor passes, the back kick can be delivered to the spine, coccyx, or kidneys.