# Brain concussion requires 80 Gs of force? **URL:** \ **Category:** Factual Questions\ **Created:** [April 29, 2018, 5:38am UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299 "2018-04-29T05:38:31Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\ **Post date:** [April 29, 2018, 5:38am UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/1 "2018-04-29T05:38:31Z")
So I found this Quora question [answer](https://www.quora.com/Can-you-get-a-concussion-from-shaking-your-head-too-hard)that says that one cannot get a concussion from shaking their head too hard or rapidly because that can’t produce 80 Gs and 80 Gs is what is required for a concussion - but yet other sources said that it is perfectly possible to get a concussion from head-shaking too rapidly…which is right? ---
**Author:** ![don\_t\_ask](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@don\_t\_ask](https://boards.straightdope.com/u/don_t_ask)\ **Post date:** [April 29, 2018, 6:06am UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/2 "2018-04-29T06:06:23Z")
You may be interested in this research published in the British Medical Journal: [Head and neck injury risks in heavy metal: head bangers stuck between rock and a hard bass](https://www.bmj.com/content/337/bmj.a2825.full) It is characteristically thorough: > [@](#): > > We can also use the theoretical model to estimate the injury levels to two of the greatest head bangers, Beavis and Butt-head. When head banging at a tempo of 164 beats per minute to “I Wanna be Sedated”9 the range of motion of Beavis’ head and neck is about 45°, which is below any injury threshold of both the head and neck injury criteria. Butt-head, however, preferred to head bang with a range of motion of about 75°. This activity is below any Neck Injury Criteron threshold, but level one head injuries are predicted by the Head Injury Criterion, with the symptoms being headaches and dizziness. It is well understood, however, that cartoon characters are able to tolerate greater than normal impacts without injury. Another legendary pair of head bangers, Wayne and Garth, head bang to “Bohemian Rhapsody” at 138 beats per minute with a range of movement of about 45°.7 Because of the low range of movement, no injuries were predicted by either the head or neck injury criteria, though the characters in the back seat of the car demonstrated a noticeably larger range of motion and might be at risk of head or neck injury. ---
**Author:** ![Delicious](https://avatars.discourse-cdn.com/v4/letter/d/dbc845/32.png) [@Delicious](https://boards.straightdope.com/u/Delicious)\ **Post date:** [April 29, 2018, 10:44am UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/3 "2018-04-29T10:44:58Z")
Wouldn’t 80G require accelerating the head at about 800m/s? I don’t think boxers punch that fast. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 29, 2018, 11:47am UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/4 "2018-04-29T11:47:26Z")
Acceleration is not velocity. 80g is 800 m/s **per second**. That doesn’t mean that you need a velocity of 800 m/s: You could also do it with a velocity change from, say, 20 m/s to -20 m/s over the course of 1/20 of a second. ---
**Author:** ![Jonathan\_Chance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jonathan_chance/32/701_2.png) [@Jonathan\_Chance](https://boards.straightdope.com/u/Jonathan_Chance)\ **Post date:** [April 29, 2018, 12:35pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/5 "2018-04-29T12:35:01Z")
As, for example, my own concussion as a teen where I flipped my bike and smacked headfirst into asphalt. I can well believe that sudden stop exceeded those limits. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 29, 2018, 1:53pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/6 "2018-04-29T13:53:48Z")
There is two misapprehensions in the o.p.p. First, acceleration is not force; a static acceleration will produce a force in proportion to the mass but to describe a force as “80 g” is meaningless. Second, and more important, in terms of damage due to a sudden impulse such as a head hitting pavement is actually due to the derivative with respect to time of acceleration, called the “jerk” by physicists. This sudden change in acceleration causes the snapping feeling when you get into a car accident or the disorientation on a rollercoaster as the vestibular system isn’t able to keep up. However, there is no instrument to measure jerk directly, so it is typically described in an acceleration time history and colloquially referenced by the peak of the measured acceleration, e.g. “80 g”; it should really be stated in a way that describes the diration and character of the acceleration history, such as “an 80 g half-sine pulse over 10 milliseconds” from which a jerk or shock response spectrum (SRS) can be calculated. As for the question of the o.p., I don’t think it would be possible to give yourself a concussion just by shaking your head, not because the human muscular system cannot produce sufficient impulse, but because a concussion requires a high differential between the motion of the skull and the brain within it, and there is too much inertial in the head for the muscles of the neck to create sufficient jerk. This requires some kind of an external force to stop the head violently. It is not a transfer of impulse through the skull and directly into the brain matter but rather the brain moving and impacting the inside of the skull, hence why hard football helments do not adequately protect against chronic traumatic encephalopathy (CTE) and may even exacerbate encouraging players to strike with the head. Stranger ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [April 29, 2018, 2:39pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/7 "2018-04-29T14:39:06Z")
> [@Stranger\_On\_A\_Train](#): > > … rather the brain moving and impacting the inside of the skull … That is one mechanism of brain injury (often referred to as “coup-contrecoup” injury) but brain damage associated with concussion is not by way of brain hitting skull, contact injuries, or even[linear, translational forces](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4090913/), but a result of _rotational_ force leading to diffuse axonal shear damage. How [much](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3979340/) rotational acceleration/deceleration it takes is dependent on many variables. > [@](#): > > …If the head motion is constrained to exclude any rotational motion, it is difficult to produce traumatic unconsciousness. In comparison, introducing or allowing a rotational component after impact substantially increases the likelihood of an unconscious episode … > > … The ability to predict the strains that appear throughout the brain during rotational motions is challenging, because the large deformations that appear during typical injury-causing situations often require advanced computational and experimental methods … [Best guess](https://www.triaxtec.com/sports/wp-content/uploads/2013/08/A-Proposed-Injury-Threshold-for-Mild-Traumatic-Brain-Injury.pdf) based on the data that exists? > [@](#): > > Injury tolerance for MTBI based on head kinematics and > HIC15 can be estimated. If the head was exposed to a combined > translational and rotational acceleration, with an impact duration > of between 10 to 30 ms, the suggested tolerable reversible brain > injury level was less than 85 G, for translational acceleration. For > the rotational acceleration, it was less than 6.0 x 10^3 rad/s2. The > suggested HIC15 value was 240. These values may change as > more human data become available. Can someone shake their head rotating it at more than 6.0 x 10^3 rad/s2? I dunno. ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [April 29, 2018, 5:10pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/8 "2018-04-29T17:10:49Z")
Also, the brain isn’t uniform or uniformly protected. Dr. Muriel Lezak, who wrote one of the excellent neuropsychology textbooks, used to tell her lecture audience that if you must take a blow to the head, try to hit from the front since the sides of the brain are much more inadequately protected from impact. This may or may not matter in the head banger scenario. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [April 29, 2018, 5:52pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/9 "2018-04-29T17:52:30Z")
[FWIW](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.469.2680&rep=rep1&type=pdf). Measured angular acceleration males maximum doing activities of shaking head less than with jumping up and down as high as possible and that max was near an order of magnitude less than the one quoted above (931.25 rad/s² with head shaking max at 216.19 rad/s²). So it seems improbable that someone without an existing predisposition (be that past injury or other) could be able to generate enough angular acceleration by shaking their head. Now the headbanging article cited concludes that a theoretical headbanger keeping a beat of 146 bets per minute with a range of 75 degrees could cause mild injury. Of note Wayne and Garth hit 138 bpm at 45 degrees but the only example they document of hitting or exceeding that rate and range is in a cartoon … Seriously I am not sure how _possible_ it is for a real person to hit that rate at that range… ---
**Author:** ![susan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/susan/32/17537_2.png) [@susan](https://boards.straightdope.com/u/susan)\ **Post date:** [April 29, 2018, 7:52pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/10 "2018-04-29T19:52:20Z")
Party on, Wayne. ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [April 30, 2018, 2:02am UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/11 "2018-04-30T02:02:23Z")
I was always taught rotational forces were more significant. But when I studied mechanics we basically used a complicated equation for acceleration that incorporated various linear, angular and Coriolis accelerations. Angular jerk might be more relevant. And people probably differ significantly - elderly people and babies have much different risk levels. It’s not that easy to study concussion — the current understanding is that it is much more common and pernicious than previously supposed. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [April 30, 2018, 12:15pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/12 "2018-04-30T12:15:06Z")
> [@Dr\_Paprika](#): > > I was always taught rotational forces were more significant. Angular jerk might be more relevant. This. When (for example) you review video of NFL concussion incidents, they almost always involve sudden starting/stopping of rotation of the head. This is supposedly why side-impact car crashes have been historically difficult to deal with: your body (including neck) gets accelerated sideways, and your head gets dragged along sideways by your neck, making it rotate, and your head comes to a sudden stop when it hits the window frame or edge of the roof. Your brain continues rotating after your head comes to a stop; the only thing that can bring your brain rotation to a stop is its connection with the brain stem. There was [a study done in the '80s](https://en.wikipedia.org/wiki/Unnecessary_Fuss) in which baboons had their heads subjected to violent rotational accelerations in an attempt to understand what sorts of accelerations were required to reliably cause brain injury; the rotations weren’t far enough to cause neck injuries, but they were rapid enough so that the brain didn’t keep up with the skull, causing the sort of shearing damage that **DSeid** mentioned. They used a machine to cause the rotations, which allowed them to deliver measurable, repeatable motions. There were ethical problems in the conduct of the study; you read about them at the Wikipedia link, or search YouTube for “Unnecessary Fuss” to see the actual injurious rotations being inflicted. I don’t know whether they actually published any results, but the nature of the research - studying rotational accelerations rather than linear accelerations - tells you where the real problem is for brain injury. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [May 4, 2018, 4:09pm UTC](https://boards.straightdope.com/t/brain-concussion-requires-80-gs-of-force/813299/13 "2018-05-04T16:09:25Z")
When I was working for a defense contractor I spent some time in the environmental test area\* and we had a new secretary poke her head in once, intensely interested in seeing a 100G test that was about to be run. “Okay, but you’re going to be disappointed,” I said. She was; the plate with the box on it hummed at about 50Hz and you couldn’t even see how far it was traveling up and down. I made sure she was there for the booster separation test where a 500-lb weight is raised about 15-degrees off vertical then released to whack against the framework with a most satisfying clang. \*Not doing anything cool, mostly gluing on the accelerometers and screwing the item down to the test bed; I didn’t even get to push the button.