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From: Frank Krygowski <frkrygow@sbcglobal.net>
Newsgroups: rec.bicycles.tech
Subject: Re: Helmet efficacy test
Date: Thu, 27 Mar 2025 19:27:12 -0400
Organization: A noiseless patient Spider
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On 3/27/2025 4:14 PM, Zen Cycle wrote:
> On 3/27/2025 1:13 PM, Frank Krygowski wrote:
>> On 3/27/2025 8:11 AM, Zen Cycle wrote:
>>> On 3/26/2025 11:28 PM, Frank Krygowski wrote:
>>>> On 3/26/2025 3:57 PM, Zen Cycle wrote:
>>>>> On 3/26/2025 11:47 AM, Frank Krygowski wrote:
>>>>>>
>>>>>
>>>>>>>> Trouble is, the protection from a bike helmet is far, far less 
>>>>>>>> than people are led to believe. Look up the standardization test.
>>>>>>>
>>>>>>> "led to believe" by what metric? I've never seen any literature 
>>>>>>> claiming a helmet _prevents_ serious head trauma.
>>>>>>
>>>>>> WHAT???
>>>>>
>>>>> No helmet manufacturer or helmet advocacy group claims helmets 
>>>>> _prevent_ serious head trauma. They _can_ reduce severity, not 
>>>>> prevent it.
>>>>
>>>> Seems to me you're focusing on the difference between "_always_ 
>>>> prevents" (which was never stated by anyone) and "can reduce severity."
>>>
>>> Yes, I am.
>>>> The latter is more honest, but is NOT how helmets are promoted.
>>>
>>> So you're saying helmets are promoted as preventing serious head 
>>> trauma, yet your only "evidence" is:
>>>
>>>> Try googling "Do bike helmets prevent serious head trauma?" After 
>>>> reading AI's "Yes" try follow the resulting links.
>>>>
>>>> And logically, if a helmet did prevent serious head trauma in one 
>>>> out of ten cases, that would justify a "Yes" answer. In those cases 
>>>> a helmet would have done what was asked.
>>>
>>> Yet there is no published literature from any manufacturer or 
>>> advocacy group which supports your claim 'thats how helmets are 
>>> promoted'. an AI answer does not qualify as marketing literature.
>>
>> I don't have a stock of marketing literature, but I suppose we can 
>> both search online. There's this: https://sonomasaferoutes.org/sites/ 
>> default/ files/lesson_7.pdf  that states "Why Are Helmets Important? 
>> (10 minutes)
>> • Ask students to articulate why wearing helmets is important (because 
>> they protect against brain injury, disability, and death). Share that 
>> helmet use has been estimated to reduce brain injury risk by 85 percent."
> 
> OK, you came up with one source - I'll give you that.

It used to be very common. It's less common now, probably because of this:

"Government agencies drop 85% helmet benefit claim

"US federal agencies The National Highway Traffic Safety Administration 
(NHTSA) and the Centers for Disease Control (CDC) have decided that they 
can no longer justify citing the claim that bicycle helmets reduce the 
risk of head injury by 85%. No subsequent research has ever found a 
benefit anywhere near as great.

"The agencies had been challenged under the Data Quality Act to show why 
they still continued to cite the earlier estimate, which is often seized 
upon to exaggerate the potential benefits of helmets and to support 
helmet laws" That's from https://www.cyclehelmets.org/1207.html?NKey=103

> We can have a semantic discussion over "protect against" vs "prevents". 
> My view is "prevents" is absolute, "Protects against" is not and is more 
> in line with "_can_ reduce severity". Your interpretation will likely vary.

Humpty Dumpty: "A word means exactly what I want it to mean..."
> 
> WRT the 85%, again, this is the first I've heard of anyone promoting 
> that. They shouldn't be doing it.

Agreed, and they never should have done it. It was on a par with "A 
daily tablespoon of our special vinegar can help you lose up to 85 
pounds in a year!!"

>>>>>>>> Well, since the helmet certification standard was established 
>>>>>>>> (essentially less than 300gs linear deceleration in a 14 mph 
>>>>>>>> impact), it became known that linear deceleration was far less 
>>>>>>>> of a problem than rotational acceleration. Twisting the head and 
>>>>>>>> brain caused far more brain injury than smacking them. But a 
>>>>>>>> helmet protrudes at least an inch from the head, providing a 
>>>>>>>> longer lever arm for glancing blows, potentially worsening 
>>>>>>>> rotational acceleration. (Note that a bare head's slippery hair 
>>>>>>>> and very loose scalp are probably evolutionary tricks to reduce 
>>>>>>>> that hazard. The helmet makes those ineffective.)
>>>>>>>
>>>>>>> a specious argument with no scientific substantiation.
>>>>>>
>>>>>> What part did you not understand?
>>>>>
>>>>> I understood all of it. What I'm stating is that you have no data 
>>>>> to support the that helmets "provide a longer lever arm and thus 
>>>>> can cause more injury" claim. Every study I've link states the 
>>>>> exact opposite.
>>>>
>>>> Well, I suppose the "thus" is not totally proven. I don't see how 
>>>> you can claim they do not provide a longer lever arm for glancing 
>>>> blows.
>>>
>>> I didn't. I wrote that " you have no data to support the that helmets 
>>> "provide a longer lever arm and thus can cause more injury" claim. 
>>> Every study I've link states the exact opposite."
>>
>> I don't see you've linked any studies that specifically address the 
>> lever arm! 
> 
> And you wont. Who would volunteer as a test subject?
> 
>> And I'll note a parallel between your previous objection on a related 
>> issue, and my statement:
>>
>> You put high value on the word "can" by saying "... They _can_ reduce 
>> severity..." to excuse the countless times they do not. Yet you're 
>> ignoring my statement where I'll emphasize: "... a longer lever arm 
>> and thus CAN cause more injury."
> 
> Nope, that's a false equivalence. "can reduce severity" is supported by 
> data, 'longer lever arm" is not.

"Longer lever arm" is supported by things like a ruler! It's a 
measurement of distance. And while I'm speculating a bit on details of 
the mechanism (using rather straightforward physics), an increase in 
concussions as bike helmet use increased _is_ supported by data.

>>> More people wearing cycling helmets means less fatal head trauma. The 
>>> result is more _non_ fatal head trauma.
>>
>> Look at the numbers, please. They're comparing 1997 to 2011 (in the 
>> same old universe!).  Wiki says 1997 had 814 bike fatalities. 2011 had 
>> 682 (one of the lowest counts ever).  That difference of 132 can't 
>> possibly be enough to explain this: “Between 1997 and 2011 the number 
>> of bike- related concussions suffered annually by American riders 
>> increased by 67%, from 9,327 to 15,546” 
> 
> 
>> You've got at least 6000 concussions you haven't explained.
> 
> Sure I have. They were wearing helmets. If they weren't there be be a 
> lot more deaths from head trauma.

You can't pretend that 6000 potential deaths were converted to 
concussions unless you had more than 6000 deaths to begin with. During 
the time period cited (and since) there have never been close to 6000 
annual cyclist deaths. Annually, they have sometimes risen, sometimes 
fallen, despite the ever increasing popularity of bike helmets.

But concussions have consistently risen. Your excuse for that is not at 
all plausible.


-- 
- Frank Krygowski