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Relating to Are one-hit knockouts possible? : It was a common trope in the 60s for heroes to knock out evildoers with a open-handed chop to the base of the neck (preferably accompanied with a high-pitched cry of 'Kee-YAH!'). I believe the claim is that a brisk thump 'stuns' the vagus nerve and down goes the bad guy.

Obviously, boxing and MMA show that there are certain spots (the temple, the jaw) that are more likely than others to cause sudden loss of consciousness. But although chokeouts are common in MMA fights, I don't think I've ever seen a knockout based on a blow to the base of the neck.

Is there any truth to this form of knockout?

P.S. I'm not even going to ask, but if there's some justification for the Vulcan nerve pinch, I'd consider that on-topic...

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    Not an answer to the question, but the systems I've done (or at least hung around the dojo with) that teach an knifehand blow to the base of the next are generally targeting the collarbone, and the purpose is to break it. – dmckee May 23 '11 at 0:15
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    I think the 'Kee-YAH!' is sufficient and the blow only here to fool us. – Zenon May 23 '11 at 17:17
  • There have been a number of knockouts in MMA due to big looping punches that land at the back of the neck, or behind the ear. For instance, I believe this is how dos Santos took out Velasquez. I don't think this is what you're asking about, but it kind of matches the term "base of the neck". – Dave May 27 '12 at 16:25
  • I've never tried this out, but in Shorinji Kenpo classes I was taught to "rake" my forearm along the jugular, rather than hit. That is supposed to interrupt the blood flow to the brain for a second or so and disorient. Never heard anything about it being able to stun. I was warned that it could be very dangerous as well if done improperly... As I said I never tried this in anger. – yu_ominae Aug 25 '13 at 23:47
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enter image description here

Of all the ways to knock someone out, a karate chop to the neck is one of the least effective and least reliable ways to do it. Actually, significant impact to the neck and cervical spine is probably more likely to result in serious neurological consequences such as paralysis rather than a simple knockout as shown on tv.

How could a karate chop knock someone out?

There are actually some plausible, if improbable mechanisms:

Vagus Nerve

enter image description here

It's possible that a well-placed strike to the vagus nerve in the neck under the appropriate conditions could render someone temporarily unconscious, however this would not be likely to last more than few seconds. This would be the most likely explanation (if it isn't staged) for the video here.

enter image description here

Sodium/Potassium Exchange

The body contains dissolved sodium, potassium and calcium, collectively known as electrolytes, which are responsible many functions, including conducting nerve impulses. These electrolytes need to remain in a very delicate balance in the body, otherwise significant problems can occur. Every time someone receives a blow to a nerve such as the vagus nerve pictured above, potassium leaves the cell and calcium rushes in, destabilizing the electrolyte balance.

The body does all it can to keep these levels balanced. With each successive strike, this balance becomes harder for the body to maintain. When the body reaches the point where the damage outweighs the body's ability to repair itself, the brain shuts down to fix the injured neurons, and the person becomes unconscious. An abstract outlining the way electrolytes behave in nerve conduction can be found here.

However, this process usually requires repeated strikes, such as in a boxing match, and a single karate chop to the neck is probably not likely to have this effect.

The "Whiplash" Effect

First, the term "whiplash" is not a medical term, but I think most people can understand what it means in this context.

enter image description here

It is possible, if struck hard enough in the neck, to cause coup-countrecoup injury to the brain by essentially rattling it around inside the skull and causing a concussion or other injury. Of course, in this situation, you have all the same problems you would have with a direct blow to the head as discussed in the other question.

It’s important to know that coup-contrecoup injuries can happen as the result of trauma without direct impact to the head, since it is the movement of the brain inside of the skull that causes the injury.source

Although this is highly improbable from a single karate chop. If anything, that karate chop of significant force would more likely result in damage to the neck, soft tissue, and cervical spine.

The Vulcan Nerve Pinch

Sorry, it only works if you're a Vulcan, or LoneStar...

enter image description here

  • in the BBC Documentary from the 1980's The Way of The Warrior, Shorinji Kempo - A new Way episode, a Martial Arts instructor in Japan showed advanced students how to render a subject unconscious with a single blow to the side of the neck, then use another technique to wake the person up...see it on YouTube at around 32 minutes in – Our Man in Bananas Apr 9 '15 at 17:51
  • Without seeing that part of the video, I would be HIGHLY skeptical of such a claim. Are the subjects of the attack also the instructors (willing) students? The power of group cohesion in martial arts will result in students flying through the air at the lightest touch from their sensei. – Graham Aug 10 '15 at 19:10

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