A kick is a physical strike using the leg, in unison usually with an area of the knee or lower using the foot, heel, tibia (shin), ball of the foot, blade of the foot, toes or knee (the latter is also known as a knee strike). This type of attack is used frequently by hooved animals as well as humans in the context of stand-up fighting. Kicks play a significant role in many forms of martial arts, such as capoeira, kalaripayattu, karate, kickboxing, kung fu, MMA, Muay thai, pankration, pradal serey, savate, sikaran, silat, taekwondo, vovinam, and Yaw-Yan. Kicks are a universal act of aggression among humans.