That's really interesting and it makes a lot of sense to me. My son's ski helmet looked pretty much ok after his crash but he still sustained a serious TBI because his helmet didn't do anything to mitigate the accelerations that his brain experienced. It did, however, protect him from a skull fracture or penetrating injury. The mechanism of injury in his case was deceleration in a 6-10' fall and the subsequent tumbling at high speed caused shearing of the neurons as the brain basically compressed and then stretched with each acceleration/deceleration. He also had significant injury on and around his brain stem where the brain was anchored by the spinal cord.

I can't find the link now, but I saw a chart that depicted the relationship between acceleration experienced by the brain and the potential for damage. It was a nonlinear relationship - as one would expect - where there was little to no damage at low accelerations until a certain point was reached and then damaged increased fast and dramatically. I'd guess it has a lot to do with the space between the brain and the skull which I'd guess varies from person to person (we all probably know someone with lots of space....). So if you can find a mechanism to back down that curve, you get a rapid reduction in injury. That's what has me interested in the MIPS technology stuff because it apparently does just that when it's a hit to the head that sets up a rotation of the brain in the skull.

J.

There are two kinds of acceleration, linear and rotational. In the studies that I saw a few years ago concussion researchers were seeing people who had quite high accelerations of both kinds who did not receive concussions and other people who did receive concussions at fairly low levels of acceleration. At the time no one knew quite what to make of the data although they all believed that reducing both kinds of acceleration had to have some benefit. I think all of the studies I saw were from football where it is somewhat easy to put sensors in every helmet and get data on every impact since football gear weighs so much that the players won't notice a few extra grams and they all stay within range of the radios that gather the data.

Contrary to what some of you seem to think the traditional helmet does an excellent job at reducing linear head accelerations during impacts. In fact the helmet testing standard measures acceleration and to pass the testing the helmet has to reduce the acceleration. If you reduce the acceleration of the head you also reduce the acceleration of the brain and in both cases the lower acceleration produces lower forces on both the brain and the skull. The standards we have were based on skull fracture testing on human cadaver skulls. The researcher determined that below 500 g's the probability of skull fracture dropped to zero and the standard was eventually lowered to 300 g's, just to be safe, I presume. Unfortunately when linear accelerations alone are considered you sometimes can get a concussion from sub 100 g impacts but you might not get one from much harder impacts. The situation was the same when they started measuring rotational acceleration data. But even if we don't know exactly what a safe acceleration threshold might be or whether some other factors also have to be considered to produce a "concussion proof" helmet we are reasonably certain that reducing the total acceleration, linear plus rotational, is a Good Thing. It would be wrong to conclude that the traditional helmet has no benefit for concussion reduction however. We know that they do not eliminate concussions completely but we do not know how many they do eliminate. The best studies that I have seen say that helmets do reduce fatality rates so it would be very surprising indeed if they had no effect on concussions.

A typical adult human is tall enough that a simple fall and head strike under the right conditions can be fatal. The probability of injury or death diminishes with the height from which you fall however and the typical recumbent is low enough to the ground that I am surprised you would get a concussion from a fall on a recumbent while wearing a helmet. But some recumbents are taller than others, some of us are more susceptible than others, and I believe that with each concussion you receive your threshold for future concussions drops. I don't know what to make of some of the stories that were related above. They appear to come from reliable sources but a whole lot of people receive head impacts in ordinary life that sound far worse than the aviation results described above completely without injury. Aviation is not a normal environment however so there could be a perfect storm of risk factors involved in the aviation results.

Thanks for the input, Khutch, very thoughtful post on your part. I used the aviation examples only because of the apparent lack of other injuries to the head and what the public has come to expect when a fatality occurs from a head injury. Someone mentioned that neuron shearing had happened to their son when a TBI occurred, I have begun to hear and read a good bit about this being found, maybe this is an area that has some answers for us. I have so little physiological knowledge that most of what I read and hear is probably not absorbed, or recognized. I want to avoid having the "internet expert" syndrome, I don't know the answers.

Gary is probably wondering what the hell happened to his thread, my apologies, again. I think I will continue to wear a helmet, be careful as I can be, and enjoy riding my bicycle as much as possible. Probably what most of us will be doing anyhow. Peace.

Bill

Well, yes, the thread did migrate some from what the OP was asking, but it's been a constructive and educational discussion of what helmets do and don't do well, the progress in understanding what they need to do, and some recent improvements e.g., MIPS. Unlike most every helmet thread in the history of BF, it hasn't gone to a flame war. Thanks, all.

Some interesting stuff, Bill and khutch. I think it's good we can have a helmet discussion which doesn't get emotional or devolve into name calling, etc.

edit: MinnMan beat me to it.

Red wing blackbirds attack red helmets

Helmets: Bicycle Helmets

I consider magnesium, EFA, ALA, and curcumin to be more more protective than an ANSI or Snell certified helmet when I worry about concussions. The secondary effects are what get you....the neurometabolic cascade.

Diminished brain resilience syndrome: A modern day neurological pathology of increased susceptibility to mild brain trauma, concussion, and downstream neurodegeneration

Dietary Concerns and Concussions | The Concussion Blog

Concussions: What a neurosurgeon should know about current scientific evidence and management strategies

https://www.upmcphysicianresources.co..._SpecEd_11.pdf

BHERI | Advances in TBI Management

I went down to WalMart and couldn't find any helmets made out of magnesium, EFA, ALA, and curcumin.

Pretty much whichever one I am wearing, but I am guessing it has nothing to do with me, right?

They are helmet certifications. That's why. Look for Magnesium next to the ANDO and Snell stickers.

It will be interesting to see if the current MIPS are substantially better, or if perhaps they're the first step on a longer path. For obvious reasons, the NFL is funding a lot of concussion prevention research and I'd hope some of the resultant technologies will improve bike helmets.

But I wish I still had the leather strap helmet I had as a kid. It would be fun to try just for old time's sake.

And I wish I still had the hair I had as a kid. It would be fun to try just for old time's sake.

Hopefully, they are the first step on a longer path. The Bicycling magazine was right that enshrining the CPSC standards in law essentially froze innovation for a long time. There is a strong and largely unfullfilled need to prevent brain injuries.

The NFL needs to do something or eventually this whole thing puts them out of business either because the pool of players shrinks or the long term effects of care for 40 year olds who are exhibiting early onset dementia from repetitive hits taken in football.

That said, helmets for contact sports are a completely different animal from those for sports like cycling or skiing where the helmet is used as accident protection and a one use sort of thing. So the design criteria and construction are drastically different. Probably not a lot of carryover in the designs.

J.

I took a look and found mipshelmet.com which shows all the current offerings. There are a lot of them! Don't see a reason to buy anything else.

Shopping for the new bike or trolling for classy chicks?

White ones as well!

Here is my new helmet. But, this one is not for general usage.

Airframe Statistic - Black | Products | Ride Icon

Granted, these numbers are for m/c riders, but I wonder what they are for bicyclists.