"Helmets don't eliminate concussions" American Football

[Benz3ne]

I've given my viewpoint on it and tried to present it in a way that is derived directly from the physics of a concussion-type injury. It makes sense to me that reduction in force, given a object of constant mass colliding with the head, would therefore reduce the acceleration.
Acceleration is directly proportional to velocity, given a set time for the movement of the head, so velocity would be increased if force is increased. That velocity coming to an abrupt halt when the neck can no longer flex gives the velocity of the brain inside the skull. That increase in momentum would therefore give a higher incidence of concussion-type injuries (if repeated, of course).
If the helmet is designed to reduce force of impact, then it can result in a reduction in number of concussions (although it might not have been designed to do so - given your comments on research into injuries helmets are designed to prevent).

The cases that you're comparing in that thought experiment aren't clear. Are you describing the effect of changing the relative velocity at impact, or the mass of the head + attachments, or both?

The velocity (of anything) doesn't come to "an abrupt halt when the neck can no longer flex". There's a complicated assembly of hard and soft bits, and a similarly complicated pattern of velocity and acceleration. And a wide range of the effects of those in different part of the body.

And why do you switch to momentum in the third sentence?

Jonathan

Momentum will be what the brain will be exhibiting when travelling within the skull for a short period. The momentum of the brain will be directly dependent on the velocity. The term simply accounts for the mass also.
The velocity of the brain will come to a pretty abrupt halt. Yes, correct, it'll "slow" but it'll be a quick deceleration in the grand scheme of things.
I'm describing the effect of an impact to the head with an object, mass m (constant), at a given force. I'm suggesting that a helmet can reduce/redistribute force, so reduce forces on the brain within the head (so potentially reducing velocity, potentially reducing the likelihood of concussion) versus an unprotected head (no mitigating measures re: force or velocity therein).

[Jdsk]

I've given my viewpoint on it and tried to present it in a way that is derived directly from the physics of a concussion-type injury. It makes sense to me that reduction in force, given a object of constant mass colliding with the head, would therefore reduce the acceleration.
Acceleration is directly proportional to velocity, given a set time for the movement of the head, so velocity would be increased if force is increased. That velocity coming to an abrupt halt when the neck can no longer flex gives the velocity of the brain inside the skull. That increase in momentum would therefore give a higher incidence of concussion-type injuries (if repeated, of course).
If the helmet is designed to reduce force of impact, then it can result in a reduction in number of concussions (although it might not have been designed to do so - given your comments on research into injuries helmets are designed to prevent).

The cases that you're comparing in that thought experiment aren't clear. Are you describing the effect of changing the relative velocity at impact, or the mass of the head + attachments, or both?

The velocity (of anything) doesn't come to "an abrupt halt when the neck can no longer flex". There's a complicated assembly of hard and soft bits, and a similarly complicated pattern of velocity and acceleration. And a wide range of the effects of those in different part of the body.

And why do you switch to momentum in the third sentence?

Momentum will be what the brain will be exhibiting when travelling within the skull for a short period. The momentum of the brain will be directly dependent on the velocity. The term simply accounts for the mass also.
The velocity of the brain will come to a pretty abrupt halt. Yes, correct, it'll "slow" but it'll be a quick deceleration in the grand scheme of things.
I'm describing the effect of an impact to the head with an object, mass m (constant), at a given force. I'm suggesting that a helmet can reduce/redistribute force, so reduce forces on the brain within the head (so potentially reducing velocity, potentially reducing the likelihood of concussion) versus an unprotected head (no mitigating measures re: force or velocity therein).

So the only thing that's changing in the thought experiment is adding a helmet? What effects of the helmet are you considering... the extra mass, the energy absorption after the impact, the changed distribution of the impact on the head, the enlarged diameter ... something else?

Thanks

Jonathan

[Benz3ne]

The cases that you're comparing in that thought experiment aren't clear. Are you describing the effect of changing the relative velocity at impact, or the mass of the head + attachments, or both?

The velocity (of anything) doesn't come to "an abrupt halt when the neck can no longer flex". There's a complicated assembly of hard and soft bits, and a similarly complicated pattern of velocity and acceleration. And a wide range of the effects of those in different part of the body.

And why do you switch to momentum in the third sentence?

Momentum will be what the brain will be exhibiting when travelling within the skull for a short period. The momentum of the brain will be directly dependent on the velocity. The term simply accounts for the mass also.
The velocity of the brain will come to a pretty abrupt halt. Yes, correct, it'll "slow" but it'll be a quick deceleration in the grand scheme of things.
I'm describing the effect of an impact to the head with an object, mass m (constant), at a given force. I'm suggesting that a helmet can reduce/redistribute force, so reduce forces on the brain within the head (so potentially reducing velocity, potentially reducing the likelihood of concussion) versus an unprotected head (no mitigating measures re: force or velocity therein).

So the only thing that's changing in the thought experiment is adding a helmet? What effects of the helmet are you considering... the extra mass, the energy absorption after the impact, the changed distribution of the impact on the head, the enlarged diameter ... something else?

Thanks

Jonathan

Only the absorbent properties of the helmet in this instance, and in part the changed distribution.
I did briefly mention that this is one approach, and that the other one is the additional heft/diameter of the helmet. This discussion will never be cut-and-dry, so it's largely down to the users unless they want to race professionally, at which point they have to abide by the rules.

[mattheus]

p.s. wouldn't it be more useful to look at the data for head injuries and helmet use during boxing? Not sure we care a lot about hand injuries, not on this forum at least..

I agree. The point I was really making is that it's generally acknowledged that something that allows an increase in force to the head can result in more injury. Such as not wearing helmets, giving no reduction in force to the head.

It's not acknowledged by anyone that understands the physics.

If I stand carefully (no sudden movements, imagine I'm trying to do the least possible harm, like standing on egg-shells) on your head twice - with and without a helmet - then gravity will result in exactly the same force on your head.

[Benz3ne]

p.s. wouldn't it be more useful to look at the data for head injuries and helmet use during boxing? Not sure we care a lot about hand injuries, not on this forum at least..

I agree. The point I was really making is that it's generally acknowledged that something that allows an increase in force to the head can result in more injury. Such as not wearing helmets, giving no reduction in force to the head.

It's not acknowledged by anyone that understands the physics.

If I stand carefully (no sudden movements, imagine I'm trying to do the least possible harm, like standing on egg-shells) on your head twice - with and without a helmet - then gravity will result in exactly the same force on your head.

This is quite a specific example. In this case, the force of you standing on my head (which is held static against an object, be it my neck vertically or a kerb) cannot generate very much velocity.
If you did, instead, drop kick me in the head twice. Equal movement, equal force in your kick, and I'm wearing a helmet for the second belting and the helmet distributed/reduced the force exerted on my head, I could sustain less brain damage.

If we used your example, coupled with my statement that greater force = greater risk of injury, and I stood on your head carefully, it'd do less damage than if I was stood on your head on Jupiter (more gravitational force) or if a car stood on your head (more mass, from f = m.a).

[mattheus]

I agree. The point I was really making is that it's generally acknowledged that something that allows an increase in force to the head can result in more injury. Such as not wearing helmets, giving no reduction in force to the head.

It's not acknowledged by anyone that understands the physics.

If I stand carefully (no sudden movements, imagine I'm trying to do the least possible harm, like standing on egg-shells) on your head twice - with and without a helmet - then gravity will result in exactly the same force on your head.

This is quite a specific example. In this case, the force of you standing on my head (which is held static against an object, be it my neck vertically or a kerb) cannot generate very much velocity.
If you did, instead, drop kick me in the head twice. Equal movement, equal force in your kick, and I'm wearing a helmet for the second belting and the helmet distributed/reduced the force exerted on my head, I could sustain less brain damage.

So is it the force or the velocity that you think produces brain injuries? Where is the force applied? The velocity of what?
(It's quite easy to answer in my simple example - if you know the relevant physics - but might get harder for your drop-kick scenario. We'll see ... )


There is quite a lot of research out there about this stuff already, by the way - but if you think asking me to be your head-injury science mentor is a better way of acquiring the knowledge, I'll see what I can do. No promises

[Benz3ne]

It's not acknowledged by anyone that understands the physics.

If I stand carefully (no sudden movements, imagine I'm trying to do the least possible harm, like standing on egg-shells) on your head twice - with and without a helmet - then gravity will result in exactly the same force on your head.

This is quite a specific example. In this case, the force of you standing on my head (which is held static against an object, be it my neck vertically or a kerb) cannot generate very much velocity.
If you did, instead, drop kick me in the head twice. Equal movement, equal force in your kick, and I'm wearing a helmet for the second belting and the helmet distributed/reduced the force exerted on my head, I could sustain less brain damage.

So is it the force or the velocity that you think produces brain injuries? Where is the force applied? The velocity of what?
(It's quite easy to answer in my simple example - if you know the relevant physics - but might get harder for your drop-kick scenario. We'll see ... )


There is quite a lot of research out there about this stuff already, by the way - but if you think asking me to be your head-injury science mentor is a better way of acquiring the knowledge, I'll see what I can do. No promises

A lateral force would result in velocity of the head + brain, then when the head comes to a stop, the brain can continue movement which causes it to clatter into the inner skull wall, causing the injury (typically concussion). F = ma (again) so they're directly proportional.
Your simple example is a very specific one, so I added a more realistic scenario to the mix.
Thanks for the reminder about research on this stuff, I'll have a nosy around. I'd love for you to be my mentor, so thanks for the offer.

[mattheus]

A lateral force would result in velocity of the head + brain, then when the head comes to a stop, the brain can continue movement which causes it to clatter into the inner skull wall, causing the injury (typically concussion). F = ma (again) so they're directly proportional.
Your simple example is a very specific one, so I added a more realistic scenario to the mix.

If I kick you in the head, I might just shatter a section of skull and your head only move quite slowly.
If you're wearing a helmet (that covers where I kick you), and it's rigid enough, your head will probably start moving much more quickly.

Which is worse for your brain? Or is it mainly damaged when - as you put it - "the head comes to a stop"? So if [thought experiment time, sorry!] I kicked you into a low earth orbit, your brain would be uninjured. At least until you came into land.

[Jdsk]

If I kick you in the head, I might just shatter a section of skull and your head only move quite slowly.
If you're wearing a helmet (that covers where I kick you), and it's rigid enough, your head will probably start moving much more quickly.

For impact from a blunt shoe-like object I very much doubt that. For the main part of the skull that surrounds the brain there will be no delay in it "starting to move" from a blow that can shatter it. The energy couldn't get to where the fracture starts unless something moves.

Jonathan

[Benz3ne]

A lateral force would result in velocity of the head + brain, then when the head comes to a stop, the brain can continue movement which causes it to clatter into the inner skull wall, causing the injury (typically concussion). F = ma (again) so they're directly proportional.
Your simple example is a very specific one, so I added a more realistic scenario to the mix.

If I kick you in the head, I might just shatter a section of skull and your head only move quite slowly.
If you're wearing a helmet (that covers where I kick you), and it's rigid enough, your head will probably start moving much more quickly.

Which is worse for your brain? Or is it mainly damaged when - as you put it - "the head comes to a stop"? So if [thought experiment time, sorry!] I kicked you into a low earth orbit, your brain would be uninjured. At least until you came into land.

Any nudges/contact with the brain would be detrimental. If you did kick me hard enough to break my skull, you'd burst capillaries which would increase pressure in the skull (not good) or a fragment of broken bone would 'bop' my brain (also not good). I don't think there's a one-statement-fits-all outcome.
As long as my skull remains intact during the initial impact, sure. Or, if I collided with an asteroid (but then I'd likely have bigger problems).

[mattheus]

OK, I'm bored already.

Research what actually causes serious brain injuries in cycling accidents. There is plenty on the internet if you look.