in a lot of film & tv characters get punched so hard that they are knocked out. i was wondering how strong would the person have to be/how hard would the punch have to be to knock the person out? and how long could the person be knocked it for (realistically)? thanks so much!
We answered a question similar to this one in the article, The Force of a Knockout.
The short answer is that yes, you can knock someone out with a punch. However, it’s not the get out of jail free card that media often presents it as. When you knock someone out, you are inflicting enough damage to their brain that the brain shuts down to protect itself. A knockout is you essentially putting someone into a short term coma, and the injury is a very serious one. Normally, they’ll only be unconscious for a few seconds and anywhere longer than thirty to ninety can indicate serious injury.
You can watch about twenty minutes of The Best Boxing Knockouts of 2018, if you watch closely (it’s blink and you’ll miss it) you will see the eyes roll back in their heads as they pass out on the slow-mo. Even if they’re awake again when that knee hits the mat, the referee jumps in. If you think, “well, what about girls?” then here you go. (Warning for blood.)
That said, strength in not in the equation. The knockouts you’re thinking of are caused by precision punches to pressure points. Usually, this is a hook punch to the jaw. You can’t hit just anywhere on the jaw either. It has to be on the back, near the ear, at the point where the jaw connects to your skull. There’s a pressure point (your nerves) in the gap, which if you hit it with meticulous perfection, can cause someone to pass out. The other version is they hit them enough times in the face that the brain succumbs after being softened up by enough continuous hits.
Anyone of any size can do this, the restriction is either skill based or an incredibly lucky shot. There’s no strength restriction. The hook is not the only means of getting someone to pass out, but it is the one most people are familiar with. You can sit there and pound on the back of someone’s skull (where the bones are softest) until they pass out. There are nerve pressure points elsewhere on the body which if struck will cause the victim to pass out. You can cut off blood flow to the brain through the carotid artery with a blood choke, and they will pass out (and die if it goes on too long.) You can strike someone in the temple (where there is a gap in your skull) for direct access to their brain. You can asphyxiate someone with a standard choke, they will pass out and, if you deny their brain oxygen long enough, eventually die. You can drive someone’s face into a rising knee hard enough that they can, under some circumstances, pass out. You can bash their head into a hard surface like a concrete wall, a sink, a metal door, a wooden door, until they (again) pass out or just can’t get back up. You can also kick them in the head to deliver even more force, resulting in more damage. Upgrade this to a spin kick or a jump kick, or even a spinning jump kick if you’re feeling adventurous. In terms of force, kicks outperform punches.
Here, watch some kickboxing knockouts while we’re at it.
Again, a knockout is brain damage. You have convinced your victim’s brain that the injury inflicted to it is so serious that it must temporarily shut down in self-defense to preserve their life. If they’re down for longer than thirty seconds, their chances of long term to permanent brain injury increase substantially. And there’s always a chance something else will do them more harm in the intermediary, from the fall itself (which can kill them or cause another greater injury which kills them) to what happens after you walk away.
Fiction likes to present the knockout as the Saturday Morning Cartoon death. You can essentially kill a character without having to say you killed them while ignoring the subsequent guilt and/or consequences of murder. This is why I refer to knockouts as fiction’s “get out of jail free card”, and why you should consider the knockout carefully before you choose to apply it. A lot of fiction writers have a bad habit of thinking anything up to death is okay or preserves a character’s moral good. However, violence is everything you do to a person from short term damage to the long term injuries. There are lots of unintended consequences, which are seeds of interesting stories all on their own.
You should never trick yourself into thinking violence in any form is safe, there’s always a risk assessment and built in cost. Your brain is floating in fluid, every time you take a hit in the face you’ll be damaging it. That’s not counting the swelling, the broken noses, someone taking out your eyes with their fingers, lost teeth from the force of a hit, boxed ears disorienting you, stumbling from taking a hit to the back of your skull, losing hair or even skin when your scalp gets raked/your hair pulled, blood leaking into your eye when your eyebrow gets split or cut by your opponent’s knuckles.
Remember this adage: where the head goes, the body follows.
Protecting your head and face is your number one priority. If someone gets control of your head, they can take you anywhere they want. No matter how hard you struggle, you will go with them until you manage to break their grip. If you ever had a question about why hair pulling is a legitimate tactic, it’s because you take control of their head and you have direct access to all the nerves around your hair follicles. You can control where they go, and it hurts. Why punch someone in the nose? A) it hurts, B) it’s a soft target so you don’t risk hurting your hand on the skull’s bone plates, and C) the swelling will disrupt their ability to see which hinders their ability to continue the fight.
You’ll notice too with most professional fighters in sports that allow ground combat like the UFC, the fighters will follow their opponent to the ground and/or keep hitting them as they go down. They get pulled off by the referees. In the rush of adrenaline and focus, it can take time for someone to realize that they need to stop. You can guarantee your character will likely have gotten in consecutive hits after their opponent has fallen, doing more damage to them than is necessary because they don’t realize they’re unconscious.
The average street fight only lasts for twenty five seconds, but rarely ends in a knockout. You’re much more likely to end up putting your opponent in a position they can no longer fight than you are driving them into an unconscious state. The exception is if you intended to. You’re less likely to knock someone out with luck than you are with skill, but either way its never guaranteed because everyone’s body is different.