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The Science of Knockouts & Chokes REVISITED

By: Dr. Scott A. Weiss

If you happen to be a fight fan and watch Mixed Martial Arts (MMA), it comes as no surprise when the fighters win a fight by submission from a choke, strangle, lock, or hold.  Today, the public seems to accept and appreciate how many real fights move to the ground after striking and if you don’t have solid ground game, it will be a rough “roll” for ya.

Although it was around internationally for many years, MMA wasn’t brought into our American homes until the Ultimate Fighting Championship in 1996 via Pay-Per-View television. Back in the day of minimal rules, when MMA was more of a true blood sport, most people observed two bloodied men rolling on the ground  until someone either miraculously tapped out or until someone passed out.  Why does that happen? How does that happen?  What does one competitor do to another that forces one to simply submit and give up? This article will explore what happens physiologically when these techniques are applied to the human body.  I will also address brain injuries and what can happen from acute and chronic blows to the head.

There is no doubt about it; the techniques seen in MMA are not new.  Striking and wrestling date back to the Neolithic age of 7000 BC.  Judo and Jiu-Jitsu techniques have been around since the Samurai, but over the years, they have been adapted and refined by many martial artists throughout the lineage. The Samurai realized that striking an armed, armored, or bigger opponent sometimes proved ineffective.  They learned that the most efficient methods for neutralizing this type of enemy were techniques that were developed around the principle of using an attacker's energy against them; accepting your enemy rather than directly opposing him.  Furthermore, the idea of a smaller adversary perfecting a technique in order to submit a bigger opponent was paramount.   A smaller opponent strategically attacking a smaller joint of the adversary was unexpected and debilitating. These were all the core commandments of Jiu-Jitsu.  I must add, I personally concur with the fact that the Gracie family in Brazil both modernized and modified traditional Jiu-Jitsu into a form that is more direct and efficient today.

What happens from Striking?

When one endures several strikes to the head from a foot, fist, or soccer ball, the brain inside the skull accepts the trauma from the impact. Although the skull does protect the brain to a point, these closed head injuries are harder to assess and diagnose.

Acute traumatic brain injury (ATBI) represents the neurologic consequence of concussive and sub concussive blows to the head. Evidence suggests that ATBI may be associated with boxing, MMA, and collision sports such as American football, Rugby, and Soccer.  Thus, millions of youth, collegiate, and professional athletes are exposed to ATBI annually. Boxing is associated with a large number of deaths relative to the number of participants directly related to ATBI.

The objective of a boxing match or MMA bout is to stop the oppnonent’s ability to fight, period. The correct punch or kick to specific targets can make a fighter dizzy, weak, breathless, paralyzed, unable to focus, and possibly lose consciousness, A.K.A. the “Knock-Out” (KO). The two Major points of contact that every pugilist is aware of in order to cause the brain to spin, rotate, and are the jaw and temple.

Whereas much of the rest of a pugilist’s body is protected by bone, fat, skin, and well-developed muscle, the brain is encased only by the skin-covered skull.  It is attached to its interior by fine filaments of blood and nerve networks. One of the more common analogies used to describe the brain is as a sack of jelly, the size of two fists suspended in a box by threads on all sides. When a boxer sustains a direct blow from a fighter (Ave. Heavyweight punch = 750 lbs. /sq. in.) to the head, which has been likened to the effect of being hit by a 12 lb. padded, wooden mallet traveling at 20mph, the head rotates so fast after being hit. This allows the brain to literally bang around in the skull. This is also known as a contra-coup injury.  The resulting damage is on the surface from brain hitting against inner surface of skull.   

Consequently, different structures of the brain have different densities and each part happens to move at different velocities.  The overall result is the creation of a “swirling” effect inside the brain.  Besides bruising the different lobes of the brain, there are tears to nerve networks, tension and tearing between brain tissue and blood vessels, which may cause lesions and bleeding, and pressure waves causing differences in blood pressure to various parts of the brain with the possibility of developing large intra-cerebral clots. Sometimes the power and force of the punch is such that the brainstem receives trauma from this sharp, angular torsion the brain. This shocks the central nervous system (CNS), which swiftly causes motor deficits, coordination disruption, confusion, and sometimes syncope or a KO. A major variable in the equation of a knockout comes from a saying by the Vince Lombardi of Boxing, Cus D’Amato. He states, “It’s the punch that you don’t see coming that always has does the most damage to you”. All of these situations are medical emergencies and every fighter presents in a different way. Most of what was reviewed above is from acute trauma, but what if one endures this type of activity over several years? 


CTE, or Chronic Traumatic Encephalopathy, happens from years of continuous trauma to the brain. This is both a progressive and neuro-degenerative disease.  In the Boxing world, it was termed “Punch Drunk”, now known as “Dementia Pugilistica” by the medical community.  These types of injuries unfortunately affect 15-20% of Professional Boxers. Long-term effects are cumulative (a.k.a. Cumulative Traumatic Brain Injury CTBI) and do not show immediately after a boxing match. Most signs of damage are more likely to appear toward the end of a boxer’s career, or even after retirement.  Recent research demonstrates that signs and symptoms may start to appear, on average, about 12 to 16 years after the start of a career in boxing. The amount of ATBI seems to also be directly related to the onset of CTBI. Stretched fibers may recover after many weeks, but severed nerve fibers do not repair and consistent bruising to different areas of the brain will cause permanent changes to the brain. Meta-Analysis research purported that ex-boxers are less able to sustain natural aging of brain. Boxer’s seem to be more susceptible to diseases of the brain and therefore may be more likely to suffer diseases such as Alzheimer’s (footballer Jimm Hill) and Parkinson’s (Muhammad Ali). Forensic research and autopsies on boxers’ brains continually report that old school boxers’ brains are smaller, their surface grey matter is thinner, and their fluid-containing ventricles are enlarged because of the decrease in white matter. Now let’s explore what happens when reducing both blood and air to the brain.

What happens from choking?

A couple of years ago, I heard of a published article in a peer reviewed journal that reported a group of physicians/researchers hooked up a few Judoka to and ECG and EEG while they were being choked out in order to study the physiological responses.  These machines measure electrical activity in both the heart and brain respectively and the result were quite predictable.

The monitors showed that blood flow to the brain is indeed momentarily interrupted (surprise, surprise) and that there are temporary EEG abnormalities while unconscious, but a full recovery occurred after each choke. One student was willing to be choked out five times on the same day.  Each time he went limp, he had the same level of function that he had before. I am curious to know what baseline testing was because they did not express that clearly in this study. Furthermore, there is a lack of research on the long-term effects of being choked out and I am looking forward to seeing some of this long-term research.

With regard to oxygen deprivation the facts are as follow:

1-3 Minutes = brain cells begin to die, but survival is possible

3-10 Minutes = serious brain dmaage likely, many brain cells have dies and patient is unlikely to recover

15 Minutes = Recovery is pretty much impossible unless in extremely frigid tempereatures.

Forensic and legal literature says that if you are going to kill a person by interrupting blood flow to their brain, you need to hold pressure for a minimum of two minutes. People have been convicted of murder based on this fact.  In the law, having to hold pressure on someone’s throat for two solid minutes is good evidence ofintent. When the technique is held for less time, the victim usually wakes up as demonstrated above with the judoka studies.  This suggests that if you get choked out and the person let’s go as you hit the ground, you should recover fully. Moreover, I hear of many so-called masters who test choking on their students but they retort with knowing how to revive them immediately as part of the science. There are certain positions for this recovery based in science, but some in folklore so be cautious. At this point, we do not know how to properly recover from these injuries, except by laying the patient on their back with legs elevated, known as the Trendelenburg position. However, interrupting blood flow to the brain is not the only way to cause unconsciousness or death. There are three other methods with which you should be concerned: Bradycardia, an arrhythmia based on carotid sinus stimulation, the second method in which one becomes unconscious is known as is Positional Asphyxia, and finally, Tracheal Compression.


Bradycardia is the medical term for the slowing down of one’s heart rate. When one is struggling to lock the strangle hold in place, the crook of your elbow can stimulate this special spot on the neck known as the carotid sinus.  It is located in the wall of the carotid arteries where it divides into both internal and external branches.  Stimulation of this spot can instant nausea and a strong reflex that slows down the heart rate enough to cause death. Carotid sinus stimulation allegedly causes strong glossopharyngeal nerve (Cranial Nerve IX) impulses leading to terminal cardiac arrest. This spot is very high and fairly lateral on the neck, behind the sternocleidomastoid muscle and only an inch lower than the jawbone.  That sensor is there to tell the heart to slow down if the blood pressure going into the brain is too high. If you squeeze the vessel hard enough and increase the pressure inside of it, that sensor tells the heart, “Whoa! We gotta surge of pressure up here! Let’s lower the pressure and reduce the heart rate” to balance everything out.  The heart obediently slows down to almost nothing, at which point it can start to fibrillate and one can pass out and die. Look at what happened recently in the news to Eric Garner.  In July of 2014, in Staten Island, New York, A police officer brought this large gentleman down with a rear naked choke, causing a heart attack in the process. The cause is rare but can happen especially in unfit individuals and individuals at risk of heart disease.

A few things to be concerned with: Number one, the sensor is small and hard to get to and the chance of this happening is small but possible.  Number two, younger people with resilient and flexible arteries are almost all resistant to this reaction to carotid compression. Older people with hardened arteries are much more susceptible, as are people with any type of cardio-vascular disease. However, this has also been thought to be the genesis of death in these common cases in which the perpetrator confessed, “I was mad at her, yeah, and I grabbed her throat with my hands, but honest to God, I didn’t do anything, I didn’t kill her! She just went limp the instant I touched her!” and the autopsy is negative. So this is always something to bear in the back of your mind when practicing chokes: if your partner is the one in a thousand people whose arteries aren’t resistant to this, and if you hit exactly on the right spot, they could go limp in your hands and die without your even achieving a solid choke.

Positional asphyxia is a more common form of syncope (passing out). Basically, when one is in a breathing-restricted position and you’re pressing on an opponent’s back or diaphragm and you choke them as well, you can cause death. Again, if your choke lasts only a few seconds, this is unlikely. It is much likelier if they are hog-tied or even merely face down. I would be extremely cautious when practicing a choke on the face-down opponent. The last method is quite straight forward, especially when you consider how air gets into the lungs.

Tracheal compression is also a major method of choking. One example is the guillotine technique.  The forensic literature states that a little over 30 lbs. of force can touch both sides of the trachea together, flattening the C-shaped trachea. And you would have to really flatten the trachea to prevent any air at all from going back and forth. I have been told from a police officer it can be done easily from behind with a nightstick.  If you get your hands, or the collar, into a good tracheal compression position on your opponent, you’re probably pressing on his jugulars and carotids too, and your opponent will pass out from those long before you significantly flatten his airway. Something to remember, vessels recover completely from being pressed flat; the airway doesn’t.  They get damaged, can swell up and reduce air flow minutes to hours after the initial incident. 

If any of you have access to Spitz and Fisher, 4th edition (the $190 book volume is the bible of the forensic pathologist), on p. 447 Spitz says: “It is said that five pounds of pressure per square inch suffice to occlude the carotid arteries and jugular veins. Thirty-two pounds are required to block the airway.” And later, on p. 448 he goes on to say: “Actual compression of the airway by the noose in hanging cases is not as common as is generally believed. Supportive evidence for this includes the finding of vomitus in the airway of numerous hanging victims. Suicidal hanging by persons with an artificial opening into their airway (tracheostomy) below the level of the noose also illustrates this point. Such individuals continue to breathe while dying” (presumably, of jugular/carotid compression). “Obstruction of the airway usually elicits a struggle, a dramatic condition known as air hunger. … Judging from the circumstances in which [jugular/carotid compressed] individuals are found, there is certainly no indication that this is an unpleasant mode of death.” So, if you’re gonna choke ‘em out, and you wanna be nice, or you don’t want to elicit struggle, it seems like you would go for the five-pound vessels rather than the thirty-two-pound airway. Unless you’re old-style LAPD.


He also quotes Reay and Eisele’s fascinating 1983 article in the American Journal of Forensic Pathology. It says, “Death from law enforcement neck holds,” to say that in the judo-derived police carotid sleeper hold, “blood flow to the head is reduced by an average of 85% in approximately six seconds… Despite the apparent harmlessness of the carotid sleeper hold, occasional deaths do occur… Movement during a struggle may turn a sleeper hold into a choke hold with serious, even fatal, consequences” or even bradycardia from carotid stimulation.

Hopefully this article revealed the true science behind knockouts and chokes.  The innate danger of these skills are apparent and obviously, in the hands of the wrong person, can be extremely dangerous and even cause accidental death. I stress every instructor of these techniques to explain the seriousness and dangers of striking,chokes and strangles.




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