Warning: H*lm*t content

EuanB wrote:
Bleve Wrote:

Sure, I don't believe that helmets (or seatbelts) should be compulsory,
but if you choose not to wear one, you're an idiot.

I disagree. It means they've come to a different conclusion than you
have. That doesn't make them an idiot.

In my *opinion* not wearing a helmet is an idiotic act in most
modern road riding situations. This thread cites some research
that is inconclusive. My experience is such that I believe my helmet
saved me from significant injury.

Who are you to say otherwise? Show me the data that head injuries have
decreased per kilometer cycled as a result of compulsion and you may
have a point. Current data points to the opposite trend.

I think it's quite easy to mislead with statistics. I'm not
convinced that helmet compulsion makes a *long-term* change in
the number of people riding, and I don't think it's possible to
prove it eiter way. There's too many other variables involved to say
for sure.

I'm not even convinced that less people are riding these days,
even with all the other factors for why they may choose to drive, that
I've already outlined. I'd be suprised if there's any good quality
research (read - not done by a crusader) that shows either way.

So, it's opinions all the way. You know mine, I know yours 'nuff
said.

flyingdutch wrote:
Euan Wrote:


Then please read http://www.cyclehelmets.org/papers/c2022.pdf


Pardon my sceptisism, but what a load of HAIRY BOLLOX!!!

heh, there's a paper with an axe to grind

Interestingly, it cites stats that somewhere around 30-45%
of teenagers and adults stopped riding in the two years
after helmets were made compulsory - but also states that there
was a 35-70% reduction in head injurys reported.

Now, I didn't do super well at Uni when doing maths (I got to
do a few subjects rather more than once ), but I'd find it
difficult to draw any conclusions from that (and the author admits,
not very good quality research) that didn't suggest that there
was a significant improvement.

I'm intrigued as to the use of pedestrians as a control
group, and the reduction of head injuries there that
seem to match. There's no attempt to suggest why peds
were showing up less at hospitals with serious head injuries. Did
something change in the water in 1985?

Now, Euan, read the second last paragraph. I'll save you
the effort of finding it : "helmets undoutably prevent wounds to the
head".
My take on that paper is that it's desperatly looking for
ways to show that helmets don't work, and even then,
it has to admit it in the end, where no-one will look, after
muddying up a lot of already very muddy statistics, and somehow
claiming that white, educated people have less prangs, not that
they're more likely to wear a lid. I didn't see anything in the paper
that matched if people presenting with HI's were actually
*wearing* their lids, but I may have missed that bit, if it's in
there somewhere?

It also harps on about decining numbers of riders as a safety concern.
I
say that in the long term numbers of people riding bikes has probably
not
changed significantly because of helmet law, but *may* have changed
becase now
joe average can afford two cars. Or maybe not. But you don't know
either way.

At the end of the day, that paper is all guesswork. There's way too
many variables to come up with any real evidence over the long term
either way, but
one thing's for sure, helmets do reduce impact forces on heads, and
light bicycle helmets add bugger-all weight (mine's 200-odd grams and
isn't
sticking out like a pendulum, my hair, when wet and long, probably
weighed more ...) compared to motorbike helmets which are very
heavy and may well increase the injury rate for rotational force
crashes. I reckon the tradeoff is so minor that the inconvenience
of a helmet (worrying about helmet-head? That wind will blow your
hair all over the shop anyway .... you'll still have to brush it
if it's an issue) is far outweighed by the (even if it's very slim)
reduction in the severity of some classes of head injury.

Euan wrote:
"Theo" == Theo Bekkers writes:

Theo Resound wrote:
And, importantly, it's only recently that we've been moving at
greater than running speed. Hit the ground at 20kph and you're
okelydokely. Hit the ground at 40kph and you're much more likely
to break something important. Not always of course, but doubling
impact speed is always going to skew your results more than a
touch.

Theo Err, if you fall off your bike you will hit the ground at
Theo approx 20km/h regardless of the speed at which you are
Theo travelling. This is the design spec of bike helmets. Should
Theo you have a horizontal velocity of 40 km/h you will still hit
Theo the ground at 20km/h.

I don't think that's correct.

It is, and you even say why below

When there are two or more velocities what we have a vectors. We have
the horizontal component (40km/h) and the vertical component. The
vector simplistically is the root of the sum of the horizontal squared
and the vertical squared.

For the cited figures that gives a velocity of 44km/h on point of
impact.

A combination of kinetic absorption and friction dissipates the
velocity.

Indeed it does. Friction (and tumbling losses) absorbs (read - grinds
....) the horizontal component, and the padding/shell
fracture/compaction absorbs the vertical.

Get a pumpkin, put it on the end of a 2m pole. Tip it onto the ground*
from ~2m, and then push it along the ground, and see what happens to
it.
Then, put a helmet on another pumpkin and try the same experiment.
Compare the two pumpkins. Imagine the surface of the pumpkin is
your skin and the contents, your brain.

Motorbike helmets are designed to deal with two issues -
immediate concussion, for which they will protect a skull
from damage at impacts of anything up to 20km/h or so (any more
than that, and you're rooted, helmet or not), and grinding, which is
why
they have a hard, slippery shell, so they'll slide more than grind, if
possible. My bike helmet also has a low-friction shell around
it, I presume for the same reason. My motorcycle pants are
lined with kevlar for abrasion resistance (check this stuff out :
http://www.dragginjeans.com.au/productTesting/index.htm ) to
deal with the horizontal component of a meeting with the ground.
I tested them once, 60km/h. Minor bruise (vertical component was maybe
1.5m or less falling onto fat & muscle padded bone), the kevlar
did its job of taking care of the sliding. Do the vector sums
your way, and I should have smashed my hip.

One day you want to have a look at my old motorbike helmet, the one I
crashed in.
It's nicely ground away along the side. No helmet, and I reckon I'd be
having some pretty decent scarring! Does a
bicycle helmet do the same? Not as well, but it does provide some
seperation from the ground if done up properly, which I think would
help a bit.

Now, what were you saying again? Helmets don't work, that's it, I
remember now Judo training would help eh? I did jujitsu for
more than your cited month, and the pushbike crash I had was not in the
least
affected by it. There was absolutly *no* time to fall correctly. I was
clipped in to my bike and flung backwards by the impact with the other
rider I ran into, and landed on the back of my head.

The helmet worked. It broke, my head didn't. I didn't even bleed my own
blood.
Get it?

* - dry concrete or bitumen, the local park with long, wet grass is
cheating

dave wrote:
Gemma_k wrote:
"Bleve" wrote in message
ups.com...

Euan wrote:

"Bob" == Bob writes:

Bob The only link is that mandatory wearing of helmets, at one
Bob point in time, discouraged cyclists, reducing cyclist
Bob numbers. I think everyone is over that by now - does it really
Bob discourage anyone anymore?

Absolutely. It's a hot and smelly inconvenience which is off-putting to
the fashion conscious.

Stackhats went out in, oh, 1980? Modern helmets are light, well
ventilated and comfortable.


You miss the point. It doesn't matter how good a helmet is to wear, or how
safe you feel in one, or how many vents there are or what kind of hairstyle
you have. It's all about the choice of whther you WANT to wear a helmet,
rather than mandating that you do....
Gemma



Yup

And if you wanted sensible effective legislation mandating stuff for
safety (and I dont) Then legislate for gloves, your hands always hit
the road.

Except in extreme cases (degloving etc) hand injuries in
bike accidents are minor scrapes or abrasions (painful, but not
long-term
incapacitating), and occasional broken bones.
Broken fingers heal reasonably well (my hands still work, I've
busted a few!). That said, I very rarely ride without gloves on on
bitumen or concrete.

As always, where you draw the line is arbitary

Bob wrote:
"Euan" wrote in message
...
... Dr Dorothy Robinson's concern, instead, is bicycle safety. She has
just published a study in the Health Promotion Journal of Australia that
is likely to send shock waves through Australian cycling communities
with its claim that mandatory bicycle helmet laws increase rather than
decrease the likelihood of injuries to cyclists.

http://melbourne.citysearch.com.au/profile?id=53571

Personally I'd still use a helmet in winter 'cause it's a handy place to
put lights :-) Summer I'd leave the lid behind and wear a sun hat.
--
Cheers | ~~ __@
Euan | ~~ _-\,
Melbourne, Australia | ~ (*)/ (*)

That article is a load of ****.

Which article are you refering to? The article in he Health Promotion
Journal of Australia is well reserched. It draws on traffic research
going back to the first formulation of Smeed's law, published in 1949
and replicates a recent study by Jacobsen (1) in 2003.

It is not publically available on the web but you can find most of
points that Dr. Robinson makes in that paper at
http://agbu.une.edu.au/~drobinso/SNrv.pdf.

(1)Jacobsen, P. L. (2003). Safety in numbers: more walkers and
bicyclists, safer walking and bicycling . Injury Prevention, 9,
205-209.

Peter Keller wrote:
On Mon, 22 Aug 2005 20:26:55 +1000, Claes wrote:

Much clipped

I think my head probably would crack. However i am not volunteering for
the experiment!
Helmets are certified up to a direct blow of 20kph (very simply put) Such
a blow will not reliably crack my skull. French research seems to show
that at direct blows of more than 23kph, the polystyrofoam shatters rather
than squashes, thereby offering no energy absorption whatsoever! No, to
keep myself as safe as possible in traffic, I am not going to rely on a
h*lm*t, even if the stupid law forces me to wear one.

peter

Peter, would you have a reference to that French research? It sounds
interesting.

John Kane
Kingston ON Canada

ritcho wrote:
Euan Wrote:
.... Dr Dorothy Robinson's concern, instead, is bicycle safety. She has
just published a study in the Health Promotion Journal of Australia
that
is likely to send shock waves through Australian cycling communities
with its claim that mandatory bicycle helmet laws increase rather than
decrease the likelihood of injuries to cyclists.

http://melbourne.citysearch.com.au/profile?id=53571

Personally I'd still use a helmet in winter 'cause it's a handy place
to
put lights :-) Summer I'd leave the lid behind and wear a sun hat.
--
Cheers | ~~ __@
Euan | ~~ _-\,
Melbourne, Australia | ~ (*)/ (*)

Dr Robinson is a well known anti-helmet law campaigner and does some
pretty good research. However, I'm concerned that her pre-determined
conclusions undermines her work.

This is always a problem in research. However it is not easy to poke
holes in her work. Or to rephrase that I have not seen anyone do it.

On the other hand some of the 'classic' papers supporting helmet use
are so full of holes that you can drive a truck through them. The real
classic Thompson, Rivara & Thompson NEJM (1989)is terrible. It calls
itself a case control study but it is not since there is no matching on
anything like revlevant variables and it goes rapidly downhill from
there. And then there was the study that didn't manage to show any
higher injury rate by non-helmet wearers abut which, seeming were
unaware that there data showed that helmet wearers were more likely to
get into crashes (Wasserman et al. Am. J. Sports Med. 1988), and then
there was the paper by Cook & Sheikh,BMJ (2003) where their figures
once corrected for a simple mathmatical error show that a helmet
prevents something like 186% of all head injuries.

It is pretty hard to take much of the pro-helmet reseach seriously. It
is riddled with errors omissions and in some cases, outright blatant
bias. The Attewell et al.(AA&P 2001) meta-analysis comes to mind.

And after that we have a number of pro-helmet organizations making
claims that helmets are effective with little or no understanding of
what they are talking about. For an interesting example of this see
http://www.casm-acms.org/PositionSta...ikeHelmets.pdf. Among
other things the authors here managed confuse 15km/h and 15 miles/hour,
apparently misread an article about motorcycle and cycling injuries and
so on. Heck, as I mentioned above the Thompson, Rivara and
Thompson(1989) paper is a 'classic'. They referenced as Thompson,
Rivers et al.

John Kane
Kingston ON

alex wrote:
Euan wrote:
... Dr Dorothy Robinson's concern, instead, is bicycle safety. She has
just published a study in the Health Promotion Journal of Australia that
is likely to send shock waves through Australian cycling communities
with its claim that mandatory bicycle helmet laws increase rather than
decrease the likelihood of injuries to cyclists.

http://melbourne.citysearch.com.au/profile?id=53571

Personally I'd still use a helmet in winter 'cause it's a handy place to
put lights :-) Summer I'd leave the lid behind and wear a sun hat.
--
Cheers | ~~ __@
Euan | ~~ _-\,
Melbourne, Australia | ~ (*)/ (*)

Maybe the annual research report was due and someone was low on
publications

Actually a good point. But that does not subtract from the fact that
she's been publishing in internationally recognized journals on this
topic for years.

John Kane
Kingston ON Canada

"Bleve" == Bleve writes:

Bleve Euan wrote:
"Resound" == Resound
writes:

Bicycle helmets absorb kinetic energy (KE). The formula for
KE is:

KE = 1/2 * M * V^2


Resound That does make a bit of difference, dunnit? I do wonder how
Resound constant the energy dispersion of a helmet relative to
Resound speed is though. Probably not a squared function though.
No idea, I'm not an engineer. I've just got basic physics under
my belt and I can remember some equations and Google what I can't
:-)

Bleve You also forget that forces work in directions. 35km/h
Bleve horizontally is mostly irrelevant* when you fall down from 2m
Bleve under the influence of gravity. A bike helmet won't do squat
Bleve at 35km/h to dead stop, but that's not the point.

See post on vectors. The horizontal component can be far from irrelevant
--
Cheers | ~~ __@
Euan | ~~ _-\,
Melbourne, Australia | ~ (*)/ (*)

"Claes" == Claes writes:

Claes Euan Wrote:
"Theo" == Theo Bekkers writes:

Theo Resound wrote:
And, importantly, it's only recently that we've been moving at
greater than running speed. Hit the ground at 20kph and you're
okelydokely. Hit the ground at 40kph and you're much more
likely to break something important. Not always of course, but
doubling impact speed is always going to skew your results
more than a touch.

Theo Err, if you fall off your bike you will hit the ground at
Theo approx 20km/h regardless of the speed at which you are
Theo travelling. This is the design spec of bike helmets. Should
Theo you have a horizontal velocity of 40 km/h you will still hit
Theo the ground at 20km/h.
I don't think that's correct.

When there are two or more velocities what we have a vectors. We
have the horizontal component (40km/h) and the vertical
component. The vector simplistically is the root of the sum of
the horizontal squared and the vertical squared.

For the cited figures that gives a velocity of 44km/h on point of
impact.

A combination of kinetic absorption and friction dissipates the
velocity.

Claes Why do you get in to vectors when you do not know what they
Claes mean? The vertical component of it, is what give you impact
Claes against the ground, that is what the helmet should
Claes absorb. The horizontal component gives rotation, you could
Claes argue that the helmet makes that worse, since the radius of
Claes the helmet is bigger than the head. You could also argue that
Claes the friction of the helmet against the road is lower, and
Claes that helps to minimise the rotation. It also gives road rash,
Claes where the helmet does help. Again, if your horizontal
Claes component is 50 km/h and you hit a boulder straight on, well,
Claes helmet or not, you die.

I do know what vectors mean. I've demonstrated that perfectly well.
If I've erred with vectors you've not demonstrated where I've erred.

You're under the mistaken impression that only the vertical contributes
to the impact speed. You are wrong.
--
Cheers | ~~ __@
Euan | ~~ _-\,
Melbourne, Australia | ~ (*)/ (*)