Helmets - again

maviczap wrote:

No matter how good the helmet, it does nothing to prevent the brain bashing against the inside of the skull, because of the massive deceleration forces involved in any crash. It will help prevent the skull breaking but not the bruising to the brain, and swelling of the brain which is what's going to cause problems.

 

That is exactly what the research was investigating, as does some existing tests.

maviczap wrote:

No matter how good the helmet, it does nothing to prevent the brain bashing against the inside of the skull, because of the massive deceleration forces involved in any crash. It will help prevent the skull breaking but not the bruising to the brain, and swelling of the brain which is what's going to cause problems.

 

That is precisely what it helps prevent, by providing a crumple zone, which provides a deceleration zone. Helmets aren't to stop the skull being broken (the skull is much much stronger than a helmet) it provides a crumple zone, much like on your car. When your head hits the ground there is no deforming material that will absorb any energy, so the skull undergoes a massive deceleration (deceleration is inversely proportional to the distance available for deceleration) so if your helmet provides 5 mm of deformation compared to 1mm of deflection of your skull, then you have reduced the brain's deceleration to one fifth. If the original deceleration was 50g, which is undoubtedly traumatic, you have reduced it to 10g, which is probably no more than banging your head hard against a table.

madcarew wrote:

maviczap wrote:

No matter how good the helmet, it does nothing to prevent the brain bashing against the inside of the skull, because of the massive deceleration forces involved in any crash. It will help prevent the skull breaking but not the bruising to the brain, and swelling of the brain which is what's going to cause problems.

 

That is precisely what it helps prevent, by providing a crumple zone, which provides a deceleration zone. Helmets aren't to stop the skull being broken (the skull is much much stronger than a helmet) it provides a crumple zone, much like on your car. When your head hits the ground there is no deforming material that will absorb any energy, so the skull undergoes a massive deceleration (deceleration is inversely proportional to the distance available for deceleration) so if your helmet provides 5 mm of deformation compared to 1mm of deflection of your skull, then you have reduced the brain's deceleration to one fifth. If the original deceleration was 50g, which is undoubtedly traumatic, you have reduced it to 10g, which is probably no more than banging your head hard against a table.

And yet so often we see broken/split/cracked helmets were that has not occured at all. That 'crumple zone' as you put it is sometimes effective at low speeds but only proven so in very strange and 'best case' scenarios, like falling onto the top part of your head onto a flat stationary surface from a walking speed and even then it will often not be enough to prevent a concussion or serious head injury. The vast majority of the forces will have been absorbed by the skull/brain.

The evidence proves precisely that helmets rarely ever prevent what you are trying to establish based on theoretical numbers in a lab/test environ which are rarely ever replicated in real life. this is in part why helmets fail so badly to have an effect on safety.

You cotinue to ignore the fact that many head strikes would never occur at all if a helmet were not worn, you continue to attribute any saved life/head injury as being the result of helmets just liuke Rich_cb does. 

Again the data revealed in the Virginia study clearly states that despite big increases in helmet wearing deaths/injuries are at a high since 1991 and that almost half of all dead cyclists were wearing helmets, that's hardly an indication of increased safety through helmet wearing is it?

Want to check the stats for Canada, I did, injuries/deaths have risen since helmet wearing became a thing, there's a massively high % of helmet wearing in Canada, it's not improved matters it's made it worse.

Keep believing your hypothetical numbers, it's total pony and the deaths and injuries to people on bikes keep mounting up, people like you and others are dangerous, not just to yourselves but the rest of us too and sadly that not just with regards to head injuries but all types of injuries as well as the other massive negative effects helmets have on people on bikes.

Jimmy Ray Will wrote:

Cracked a helmet once, dropping it from waist height on to a flat surface. Are there any physics experts that could calculate the sort of energy a 250gram object falling from 1m would generate before impact? I can't help but feel that it wouldn't be a lot. 

Well thinking back to GCSEs

F =MA  =0.25 x 9.81 = 2.45Newtons of force

Deeferdonk wrote:

Jimmy Ray Will wrote:

Cracked a helmet once, dropping it from waist height on to a flat surface. Are there any physics experts that could calculate the sort of energy a 250gram object falling from 1m would generate before impact? I can't help but feel that it wouldn't be a lot. 

Well thinking back to GCSEs

F =MA  =0.25 x 9.81 = 2.45Newtons of force

Er, no.

OP asked for *energy*

Gravitational potential energy converted to kinetic energy = mgh = 0.25 x 9.81 x 1 = 2.45 joules

Whether that cracks a helmet depends a bundle of other things: the time duration of the impac (affects the decceleration and hence the force applied to the helmet), how concentrated the resulting force is, the shape of the helmet in the impact area, whether there's prior damage you didn't see, etc, etc...

flobble wrote:

Deeferdonk wrote:

Jimmy Ray Will wrote:

Cracked a helmet once, dropping it from waist height on to a flat surface. Are there any physics experts that could calculate the sort of energy a 250gram object falling from 1m would generate before impact? I can't help but feel that it wouldn't be a lot. 

Well thinking back to GCSEs

F =MA  =0.25 x 9.81 = 2.45Newtons of force

Er, no.

OP asked for *energy*

Gravitational potential energy converted to kinetic energy = mgh = 0.25 x 9.81 x 1 = 2.45 joules

Whether that cracks a helmet depends a bundle of other things: the time duration of the impac (affects the decceleration and hence the force applied to the helmet), how concentrated the resulting force is, the shape of the helmet in the impact area, whether there's prior damage you didn't see, etc, etc...

Well, the energy it takes is a bit meaningless ( how many calories is your helmet rated at!?), so i interpreted what he really was asking for was force . As you go on to explain in your post, it's the force and how its applied that is actually meaningful to the capacity of a helmet..

Deeferdonk wrote:

flobble wrote:

Deeferdonk wrote:

Jimmy Ray Will wrote:

Cracked a helmet once, dropping it from waist height on to a flat surface. Are there any physics experts that could calculate the sort of energy a 250gram object falling from 1m would generate before impact? I can't help but feel that it wouldn't be a lot. 

Well thinking back to GCSEs

F =MA  =0.25 x 9.81 = 2.45Newtons of force

Er, no.

OP asked for *energy*

Gravitational potential energy converted to kinetic energy = mgh = 0.25 x 9.81 x 1 = 2.45 joules

Whether that cracks a helmet depends a bundle of other things: the time duration of the impac (affects the decceleration and hence the force applied to the helmet), how concentrated the resulting force is, the shape of the helmet in the impact area, whether there's prior damage you didn't see, etc, etc...

Well, the energy it takes is a bit meaningless ( how many calories is your helmet rated at!?), so i interpreted what he really was asking for was force . As you go on to explain in your post, it's the force and how its applied that is actually meaningful to the capacity of a helmet..

Actually it's the energy dissipation that is important. The helmet is designed to work whilst wrapped around a head, not whilst empty. Hence Jimmy's 'test' has no relevance to the efficacy of a helmet. It is highly likely that had the helmet been filled with a melon when he dropped it, it wouldn't have broken, despite being 10 times heavier and the force 10 times greater.

Also, it is difficult to concieve that a helmet in good condition would break under the conditions that Jimmy describes, so it is possible, likely even, that it was already compromised.

Deeferdonk wrote:

Jimmy Ray Will wrote:

Cracked a helmet once, dropping it from waist height on to a flat surface. Are there any physics experts that could calculate the sort of energy a 250gram object falling from 1m would generate before impact? I can't help but feel that it wouldn't be a lot. 

Well thinking back to GCSEs

F =MA  =0.25 x 9.81 = 2.45Newtons of force

Close, but not quite the right equation there.

I found this site - The Splat Calculator: https://www.angio.net/personal/climb/speed.html

It seems to have trouble with putting in 0.25 Kgs, but it gives this equation for calculating the energy of a free-falling object:

Energy at splat time: 1/2 * mass * velocity² = mass * g * height

which gives: 0.25Kg x 9.8m/s² x 1m = 2.45Kgm²/s² = 2.45Nm

Oh - that's your answer (excepting the units), but only because we're using 1m as a height.

Jimmy Ray Will wrote:

Being a cynic... if I was looking to trick people into the importance of a piece of safety equipment, I couldn't think of a better way than by making it more likely that a piece of equipment will be used when worn, and making sure there were obvious signs of its effectiveness when 'used'. 

The humble bicycle helmet is beautifully marketed. 

Increase the circumference of your head so you are more likely to hit it on things, then make the helmet super fragile so that its effectiveness appears obvious. I love the way the fragility of the helmet somehow perfectly encapsulates the perceived fragility of our heads. You genuinely couldn't make it up.

At least full face BMX helmets and their ilk can genuinely provide some level of protection. 

 

I keep seeing this idea that increasing the circumference of the head increases the likelihood that it will be hit. In the vast majority of crashes (and I've had a few) I really don't see that increasing the head cicumference materially adds to the likelihood it will impact the obstacle. Does anyone have any research that shows that head strikes are more common in the wearing of cycle helmets due to the enlarged circumference of the head? 

fukawitribe wrote:

No, I don't think there is no risk compensation in sport - quite the opposite .

It's an interesting topic. I'm not sure how much of this is strict 'risk compensation' and how much is just evolution of the game and other factors... but there are definitely unintended consequences of more padding, and I'd take a punt on some of it being attributable to risk compensation. It must be really difficult to measure in a competitive environment with risks being taken anwyay.

But, a couple of examples:

Old school American Football having skull-caps to protect the head. Toughen up the helmets to become the motorbike-like ones they have today... players start tackling, ram-style, with their heads. Big news at the mo due to concussion, depression, and potentially massive lawsuits against the NFL.

Boxing: old-time bare-knucklers lasting 100+ rounds with few headshots due to the risk of broken hands. Today: 10oz+ gloves, 12 rounders (tops); broken hands are a regular scourge.

Amateur headguards were removed for male competition after 30 years of being mandated. The rationale was that they didn't decrease head injuries - in fact, increased head injuries owing to less focus on defence and increased risk taking is one of the main reasons given: https://www.iseh.co.uk/news/latest-news/new-page-44

They now have the weird situation where women do wear headguards and men don't, but, as the reason given for that is they don't have the evidence for women yet as it's a relatively young sport, and don't just want to follow the men, it does at least hint at it being an evidence-based rule.

davel wrote:

fukawitribe wrote:

No, I don't think there is no risk compensation in sport - quite the opposite .

It's an interesting topic. I'm not sure how much of this is strict 'risk compensation' and how much is just evolution of the game and other factors... but there are definitely unintended consequences of more padding, and I'd take a punt on some of it being attributable to risk compensation. It must be really difficult to measure in a competitive environment with risks being taken anwyay.

[snip]

Indeed - agree completely. The boxing one is interesting, and has a link with this study and MIPS - there is still a deal of debate about whether or not headguards caused more and/or differing injuries. One thing that came out IIRC was again the realisation that impact concussion is not simply the brain getting knocked back and forward in the skull, but there is a surprising rate of it due to tangential shots (which headguards can make worse). This was known for a long time elsewhere, e.g. in the army with oblique shot deflection from helmets, and is / was not at all obvious. If studies such as the one in the article can help hightlight such cases and get more - and better targeted - improvements in helmets as PPE from manufacturers, then I think that's a good thing for those that choose to use them.

CygnusX1 wrote:

Oooh I feel a graph coming on...

iihs.org wrote:

A total of 835 bicyclists were killed in crashes with motor vehicles in 2016. That is the highest number of bicyclist deaths since 1991.

More than half of those killed in 2016 weren't wearing helmets. Helmet use has been estimated to reduce the odds of a head injury by 50 percent.

Nice conflation of figures there.

1) Over half - so are we talking 50.00001% ?  51% ? 99% ? L

2) reduces odds of head injury by 50% Oh , estimated. Guessed, more like. 

3) And how many of those 835 deaths with/without helmets were from head trauma and how many were crush/internal organ injuries?

iihs.org wrote:

The Virginia Tech Helmet Lab currently rates football and hockey helmets, as well as soccer headgear

Who on earth wears (protective) headgear to play soccer*  ?!?!?!

Apparently, the yanks do. Jeez. Quick google for Soccer headgear reveals its rebadged rugby scrum caps or  a padded headband 

Some fine (5 star) reviews for this on their website:

"I don't know if they actually work, but I look so hardcore in them that it makes people think that I'm better than I really am."

"My daughter has used your protective headgear since her 2nd concussion and I have to say I wish more goalies and field players would wear it. When she got her 3rd concussion she hit her head against the goal post and I swear that her headgear took most of the blow. Unfortunately she just received her 4th concussion and can no longer play contact sports, but it wasn't for a lack of headgear, she got kicked in the head." 

I think the author of the first review can find the answer to whether they work in the second testimonial.

(*or football as the rest of the world calls it) 

I just can't get over 'field players'.

Sniffer wrote:

I just can't get over 'field players'.

I'd love to say that during my (very short and indistinguished) football career, I played the field like George Best or Wayne Rooney, erm, or maybe not quite like Rooney. 

brooksby wrote:

The Bristol Post is running a story about a woman up north (how does that work?) who's telling everyone they must wear a helmet when riding a bike.  This is because her son was doing stunts on his bike and face planted and had to go to hospital for very serious cuts and scrapes and stuff all across his face.  She cannot see a difference between riding to the shops and teenagers stunting.  Plus, I hadn't realised that a bike helmet would protect me from cuts and scrapes on my face...

The number of people who don't know how to wear a helmet correctly is staggering

hawkinspeter wrote:

brooksby wrote:

The Bristol Post is running a story about a woman up north (how does that work?) who's telling everyone they must wear a helmet when riding a bike.  This is because her son was doing stunts on his bike and face planted and had to go to hospital for very serious cuts and scrapes and stuff all across his face.  She cannot see a difference between riding to the shops and teenagers stunting.  Plus, I hadn't realised that a bike helmet would protect me from cuts and scrapes on my face...

The number of people who don't know how to wear a helmet correctly is staggering

 

 

Wot, no squirrel? 

brooksby wrote:

hawkinspeter wrote:

brooksby wrote:

The Bristol Post is running a story about a woman up north (how does that work?) who's telling everyone they must wear a helmet when riding a bike.  This is because her son was doing stunts on his bike and face planted and had to go to hospital for very serious cuts and scrapes and stuff all across his face.  She cannot see a difference between riding to the shops and teenagers stunting.  Plus, I hadn't realised that a bike helmet would protect me from cuts and scrapes on my face...

The number of people who don't know how to wear a helmet correctly is staggering

 

Wot, no squirrel? 

I find your lack of faith disturbing

OldRidgeback wrote:

brooksby wrote:

The Bristol Post is running a story about a woman up north (how does that work?) who's telling everyone they must wear a helmet when riding a bike.  This is because her son was doing stunts on his bike and face planted and had to go to hospital for very serious cuts and scrapes and stuff all across his face.  She cannot see a difference between riding to the shops and teenagers stunting.  Plus, I hadn't realised that a bike helmet would protect me from cuts and scrapes on my face...

 

Me and my son were BMX racing this weekend. He crashed out in his final and I'm glad he was, as is a BC requirement, wearing his full-face lid. He also had on knee and elbow pads. Despite the padding, he did fracture an elbow and has had to have surgery. He was also mildly concussed.

But this was a BMX race. It is an inherently dangerous sport, pretty much like MTB racing.

We both have been BMX racing a while and know the risks and wear the kit. But it's a lot different from riding to the shops.

so the helmet didn't prevent a concussion and that wasn't even involving a motorvehicle, doesn't sound good does it! What if by not wearing the helmet your sons head would have not actually come into contact with whatever it was he struck, you know because you increased his head circumference significantly?

How many times have you or son crashed out (in all cycle riding wearing a helmet), how many times have you hit your head between you?

Do you not see that taking more risk means more crashing/injury and you take more risk because you feel more protected? Given we know that more children die in motorvehicles solely from head injuries in E&W only than all child cyclists by all injury types in the UK would you ensure your child wears one whenever in a motorvehicle, if not why not?

BehindTheBikesheds wrote:

OldRidgeback wrote:

brooksby wrote:

The Bristol Post is running a story about a woman up north (how does that work?) who's telling everyone they must wear a helmet when riding a bike.  This is because her son was doing stunts on his bike and face planted and had to go to hospital for very serious cuts and scrapes and stuff all across his face.  She cannot see a difference between riding to the shops and teenagers stunting.  Plus, I hadn't realised that a bike helmet would protect me from cuts and scrapes on my face...

 

Me and my son were BMX racing this weekend. He crashed out in his final and I'm glad he was, as is a BC requirement, wearing his full-face lid. He also had on knee and elbow pads. Despite the padding, he did fracture an elbow and has had to have surgery. He was also mildly concussed.

But this was a BMX race. It is an inherently dangerous sport, pretty much like MTB racing.

We both have been BMX racing a while and know the risks and wear the kit. But it's a lot different from riding to the shops.

so the helmet didn't prevent a concussion and that wasn't even involving a motorvehicle, doesn't sound good does it! What if by not wearing the helmet your sons head would have not actually come into contact with whatever it was he struck, you know because you increased his head circumference significantly?

How many times have you or son crashed out (in all cycle riding wearing a helmet), how many times have you hit your head between you?

Do you not see that taking more risk means more crashing/injury and you take more risk because you feel more protected? Given we know that more children die in motorvehicles solely from head injuries in E&W only than all child cyclists by all injury types in the UK would you ensure your child wears one whenever in a motorvehicle, if not why not?

Risk compensation ?  It happened during the final of a BMX race.. and as for head injuries in  kids in vehicles go and have a look at your statistics for the details such as retention system (e.g. seat belt on or off), safety features (e.g. air bags - active when they shouldn't or not present), physiolocal factors (e.g. age of child/head to body ratio) and child seats - you want prevention of deaths in infants ? How about you bitch about the historical lack of action on rear facing child seats. FFS