A pressure point (Japanese kyūsho 急所 "vital point, tender spot";;Chinese 穴位 ; Malayalam marmam) in the field of martial arts refers to an area on the human body that may produce significant pain or other effects when manipulated in a specific manner. Techniques of attacks on pressure points, or kyūsho-jitsu, feature in various styles of Japanese martial arts, such as Daitō-ryū, Kotō-ryū, Gōjū-ryū, Sekiguchi-ryū, Yōshin-ryū, Kuma-ryū, Kōga-ryū, jujutsu, aikijutsu, kempo, Krav Maga and Ninjutsu.
The concept of pressure points is present in old school (17th century) Japanese martial arts and is claimed to have an even earlier history; in a 1942 article in the Shin Budo magazine, Takuma Hisa Sensei asserted the existence of a tradition attributing the first development of pressure-point attacks to Shinra Saburō Minamoto no Yoshimitsu (1045–1127).
Handcock and Higashi (1905) published a book which pointed out a number of vital points in Japanese martial arts.
Exaggerated accounts of pressure-point fighting have appeared in Chinese Wuxia fiction, and became known by the name of Dim Mak or "Death Touch" in western popular culture from the 1960s. One of the best known uses of pressure-point fighting was known to Trekkies as the "Vulcan nerve pinch." While it is undisputed that there are sensitive points on the human body where even comparatively weak pressure may induce significant pain or serious injury, the association of kyūsho with esotericist notions of qi, acupuncture or reflexology is controversial.
There are several types of pressure points - each is applied differently and each creates a different effect. "Pain points", for example, use tendons, ligaments, and muscles - the goal to temporarily immobilize the target, or at the very least to distract them. Reflex points produce involuntary movements, for example causing the hand to release its grip, the knees to buckle, or the target to gag, or even for the person to be knocked unconscious.  Most pressure points are located on pathways on the nervous system.
Some pressure points produce pain when struck, pressed, or rubbed depending on the point itself. While the distraction of pain might offer sufficient advantage in a fight, additionally the body has a Pain withdrawal reflex whereby it reacts to pain by moving away from the source. Martial artists can make use of this through minimal effort. Applying pressure to the collar bone from above will cause the subject to move downwards, whereas poking them upwards in the gap between the ear and neck will make their body want to move upwards. Pressure to the shoulder causes that side of the body to move back. A jab to the abdomen in the middle of the stomach will cause some people to twist around, away from the pain. A rapid impact - say from an elbow or fist - to the solar plexus can easily knock all the air straight out of a victim, leaving them gasping for air and unable to move. A rub down the back will cause the body to move forwards. Some points react more violently to pain from changes in the pressure (rubbing) rather than constant pressure. Applying pressure to the nose, the temple or the testicles will also cause significant pain.
The baroreceptors in the carotid artery are pressure-sensitive, supplying the brain with information to control systemic blood pressure. Pressure against this region will send signals which indicate that blood pressure is too high and lead to a lowering of blood pressure. Therefore striking this area can cause unconsciousness using the same mechanism, also relying on the force being transmitted to the reticular activating system.
There are joints that when struck, can be hyper-extended and even tear. This is a technique which can cause permanent damage to one's opponent. There are two types:
The brain is a sensitive organ which floats in a fluid (cerebrospinal fluid) and balances on a very flexible spine. These safety mechanisms allow the head to take substantial impact without resulting in concussion, but which can still cause permanent brain damage. However, martial art techniques can be delivered in a way which effectively eliminates such protections, thus causing disorientation or instantaneous knockout. The most commonly taught technique involves a strike just below the occipital ridge, at the correct angle in the correct direction. Another well known point with this effect is the chin or lower jaw, giving rise to the boxing expression: a "glass jaw". The same effect of knocking somebody unconscious may be achieved by using the edge of the hand (palm-up) to apply a sharp strike to the carotid artery.
Some believe there are energy channels (acupuncture meridians) which allow Ki to flow through the body. Acupuncture is the best known use of the meridian system. Traditional Chinese medicine practices are largely based on the idea that meridians are specific pathway lines in the human body, along which are found many hundreds of acupressure points. There is no physically verifiable anatomical or histological basis for the existence of Ki, acupuncture points or meridians.
According to these legends, attacks will impact the flow of Ki, and thus the body. Therefore pressing, seizing or striking these points with specific intent and at certain angles is believed to cause either a heightening or diminishing of Ki circulation in the body. Arts such as Bak Mei and Bok Foo Pai utilize this strategy almost exclusively in combat.