Are Knockouts Safe?

Are Knockouts safe?

I do not offer knock-out chokes (sleepers) during a session, because I believe they come with a risk. Even if you take full responsibility for your own well-being, I will not repeatedly knock you out. I feel responsible for your physical well-being during a session.

I do not mind inflicting pain, but I will not seriously harm or injure you. And a sleeper could harm you. It could cause immediate and serious damage and there is no evidence that even when you wake up feeling okay you won’t suffer from damage occurring long after. In fact, there are reasons to assume that you are risking your brain’s health on the long term. Especially when repeatedly being put to sleep.

I’ve written this text, not to convince you of anything but to explain why I don’t offer knock-outs during sessions, and to offer you some information. 

I will start with explaining how a sleeper works, after which I will explain why it can be dangerous: risk of immediate injury (a stroke), an increased risk on suffering a major stroke in the future (a silent stroke) and brain damage on the long term.

How a Sleeper Works

A sleeper is a choke whereby the carotids are narrowed by applying pressure, limiting or cutting off the blood flow to the brain and causing loss of consciousness. The carotids are two arteries (major blood vessels) running from the aorta in the chest and up through either sides of the Adam’s apple. They supply blood (with fresh oxygen) to the brain, neck and face. If you squeeze them you deprive the brain from oxygen.

You can compress the carotids, by using your biceps, wrists, forearms, ankles or your opponent’s gi without cutting off the airways to the lungs, meaning the object can still breathe. (Think of a Rear Naked Choke.) It is a comfortable way to pass out, and in rule the object will wake up after seconds.

If you want to decrease the risk of damage you should let go of a chokehold immediately when someone passes out. Therefore you should always be able to notice a pass-out.

This is why I always pay very close attention to the face and other physical signs of consciousness. I once applied a choke to someone who turned out to pass out very easily. My 6-second rule (applying pressure no longer than 6-7 seconds) wasn’t sufficient. The person passed out after 4-5 seconds. Releasing them immediately, they woke up before the hand they were holding up even touched the mats.

Ten Seconds

When the blood flow to the brain is cut off for more than about thirty seconds, some brain damage is guaranteed. How long it takes to pass out depends on the individual who is being choked, as the example above proofs. Some pass out after one of the carotids is squeezed for five seconds and others pass out when both are squeezed for fifteen seconds. On average it is about nine seconds from the moment the blood flow is cut off properly.

The following goes for most human beings: after fifteen seconds someone is unconscious. After thirty seconds there is brain damage. After five minutes the brain is dead.

Immediate Injury

There are multiple ways in which a blood choke can injure someone. An example of an immediate injury is a stroke. Serious injury can occur when a carotid is damaged. A damaged carotid can produce blood clothes. If one travels to the brain it can trigger a stroke.

Complications can be caused by congestion of your carotid. Like anywhere in the arteries plaque builds up in the carotid during life. If your carotid is congested the plaque could break off and this could also lead to a stroke. The older you are, the higher the risk this happens. Arteriovenous malformations or defects in blood vessels can precede a worst-case scenario for choking-related injury.

Sean Entin

What does it mean to have a stroke? Without going into further details: a stroke-causing choke can fuck you up. An example is Sean Entin, who was put in a choke during training. He didn’t even go completely out but six weeks later he collapsed. It is strongly recommanded by medical experts to be overall extremely careful with chokes if you are above 40.

Silent Stroke

A stroke does not have to have any outward symptoms. During a silent stroke the person is typically unaware they have suffered a stroke. Despite its lack of identifiable symptoms, a silent stroke still cause brain damage and places you at increased risk for a major stroke in the future.

A Properly Applied Choke

Techniques as thought in judo, bjj and other sports mostly focus on applying pressure to the carotids, because it is the fastest way to have someone lose consciousness. If you are applying a blood choke carefully with the purpose of knocking someone out, you shouldn’t apply too much pressure to the carotids. The choke should also be technically correct and this means avoiding two things.


Firstly, you shouldn’t cut off the airflow to the lungs and thus make sure there is no pressure applied to the airways. Avoiding cutting of the airflow decreases to risk on (brain) damage. If someone can’t breathe they will naturally panic and tap, though. Which is different with oxygen deprivation to the brain. It is easier to endure until you pass out.


Secondly, you shouldn’t compress the internal jugular veins in the neck, because this prevents blood flow from the head to the heart. A worst-case scenario would be compressing the internal veins in the neck and not the carotid arteries, because then blood flows to your brain but it can’t flow out. It is somewhat more problematic than only cutting off the blood flow to the brain or compressing both. I do believe it is relatively hard to compress these internal veins. It’s more likely to happen when pressure is applied with the legs.

I concluded the second situation is more harmful based on forensic medicine books on causes of death. So don’t worry, a choke is unlikely to harm you if you tap on time and stay conscious.

Long-Term Damage

Even if applied technically correct and with care, you are in fact still depriving the brain from oxygen when choking someone till they pass out. And although it takes several minutes before brain cells will actually die off, there is evidence that unconsciousness can cause damage and scientists have reasons to assume that repeated unconsciousness will cause certain damage.

No Studies

The real life effects of repeated unconsciousness as a result of cutting off the blood flow to the brain have not been studied. However, it might be useful to have a look at research focussing on the health effects of repeated blows to the head as with boxing. The results of these studies are quite disturbing.

Brain Damage in Boxers

Research has proved that most boxers suffer from permanent brain damage of various degrees resulting in memory issues, mood swings, lowered IQ, poor judgment and impulse control and so on.

And then an estimated 20% of boxers have Chronic Traumatic Encephalopathy of which the symptoms can occur long after quitting boxing and even without previous symptoms. Including: memory loss, depression, anxiety, Parkinson, dementia and shortened life expectancy. CTE doesn’t show on CAT-scans and can only be determined with certainty by examination after death. The estimated 20% might thus be much higher. (Signs of CTE were found in 99% of NFL football players who were examined post-mortem.)

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease associated with repeated head injuries, such as concussions. Although the exact mechanisms leading to CTE are not fully understood, there are several theories on how concussions might contribute to its development: impaired cellular repair mechanisms, axonal injury, blood-brain barrier disruption, inflammation and tau protein accumulation.

Tau protein

What we know is that oxygen deprivation releases and can cause accumulation of tau protein. Under normal circumstances, tau helps to stabilize the structure of neurons. However, in CTE, the tau forms neurofibrillary tangles, which disrupt neuronal function and can eventually lead to cell death. The accumulation of tau is believed to be one of the primary pathological features of CTE.

Repeatedly Passing Out

With boxing the brain damage is not caused by a deprivation of oxygen but by concussions (whereby someone may or may not be knocked-out as well). But both deprivation of oxygen and concussion cause similar effects on the brain. Effects that have been proven to play a roll in the development of long-term brain damage.

I think it is safe to assume that repeated deprivation of oxygen (blood chokes) just like repeated concussions (head blows) potentially causes brain damage. Even minor damage resulting in mood swings, anxiety or depression some years afterwards i.e. isn’t worth risking, in my opinion. And I believe there is a risk.

Personally I am convinced that depriving the brain from oxygen is damaging but the fact alone that I can’t guarantee you won’t be harmed is enough to exclude sleepers from my offer of session activities. There is simply no evidence at all to back up the claim that blood chokes are factually harmless or harmless when applied properly.

Repeatedly passing out from a sleeper within a short period of time. I.e. multiple times during one session doesn’t seem like a good idea to me if you value brain health, both now and in the future.

Euphoric Experience

What I do understand is the reasons why someone might be seeking the experience of a sleeper. The idea is exciting and it can provide you with the ultimate feeling of physical powerlessness, surrender,  submission.


If you have experienced it before it might also actually have felt like a positive and magical experience. This makes sense.

Your brain is factually shut down for a moment. It is different from when you are sleeping. Compare it to pulling out the plug as opposed to putting your TV on stand-by. In a way it is as if you’re being reborn, taking a split second before being able to consciously process your first sensory perceptions after waking up.

Another explanation for the euphoria is the natural camaraderie that develops when you are in a position where your limbs are entwined with someone else’s for a moment longer than a few seconds. It causes a release of oxytocin (love hormone), creating feelings of warmth. This combined with the other person being an attractive woman and the state of arousal you most likely are already in during a session contributes to the euphoria when you wake up and the oxytocin hits you.

Avoiding All Risks

To summarize the risks involved with knock-out chokes:

  1. A sleeper can cause damage to your carotids and trigger a stroke. This can happen immediately or weeks later.
  2. A sleeper can cause a silent stroke without identifiable symptoms, placing you at increased risk for a major stroke in the future.
  3. Passing out repeatedly can potentially cause long-term brain damage and it most likely compromises your brain’s overall health.

Being knocked out from a choke once or twice will likely not do much long-term damage, but there is still the risk of a stroke and unfortunately I cannot estimate how healthy your veins are.
How much I would love to make you feel euphoric and how easy it might be for me, this isn’t a safe way to do it in my opinion. If you are fully aware of the risks and you still want to be knocked out, you can find girls who will be happy to choke you out. Like I said, I understand the desire and I don’t judge you for it. To me it simply doesn’t feel right to contribute to something of which I believe it can be harmful.

I would like to avoid risk of or contributing to permanent damage, even if it occurs afterwards and you won’t connect it to the session. I’d rather break your arm, from which you’ll recover and move on.

—So, can I break your arm? No?

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