A knockout (abbreviated to KO or K.O.) is a fight-ending, winning criterion in several full-contact combat sports, such as boxing, kickboxing, muay thai, mixed martial arts, karate, some forms of taekwondo, and other sports involving striking, as well as fighting-based video games. A full knockout is considered any legal strike or combination thereof that renders an opponent unable to continue fighting. The term is often associated with a sudden traumatic loss of consciousness caused by a physical blow. Single powerful blows to the head (particularly the jawline and temple) can produce a cerebral concussion or a carotid sinus reflex with syncope and cause a sudden, dramatic KO. Body blows, particularly the liver punch, can cause progressive, debilitating pain that can also result in a KO. In boxing and kickboxing, a knockout is usually awarded when one participant falls to the canvas and is unable to rise to their feet within a specified period of time, typically because of exhaustion, pain, disorientation, or unconsciousness. For example, if a boxer is knocked down and is unable to continue the fight within a ten-second count, they are counted as having been knocked out and their opponent is awarded the KO victory. In mixed martial arts (MMA) competitions, no time count is given after a knockdown, as the sport allows submission grappling as well as ground and pound. If a fighter loses consciousness ("goes limp") as a result of legal strikes it is declared a KO. Even if the fighter loses consciousness for a brief moment and wakes up again to continue to fight, the fight is stopped and declared a KO. As many MMA fights can take place on the mat rather than standing, it is possible to score a KO via ground and pound, a common victory for grapplers. In fighting-based video games, such as Street Fighter and Tekken, a player scores a knockout by fully depleting the opponent's health bar, which awards the round to the winning player. The player who wins the most rounds (by scoring the most knockouts or by having more vitality remaining when time expires during each round) wins the match. This is different from real-life combat sports, where a knockout would end the match immediately.