OT: Stanford researches measure concussion forces in greatest detail yet
http://news.stanford.edu/news/2015/january/measure-concussion-forces-010615.html
From the article:
Previous research has measured the translational forces – up/down, left/right, front/back – of concussion events, but scientists have long believed that rotational accelerations play a prominent role in the injury.
...
The mouthguards recorded more than 500 impact events sustained during regular sporting events. Two of these impacts resulted in diagnosed concussions, and are believed to be the first-ever concussion events to be recorded with six degrees of freedom.
Statistical analysis of the impacts revealed that measurements made with six degrees of freedom were more predictive of injury than those made with the standard three degrees of freedom. They also found that rotational accelerations were a stronger predictor of injury than translational forces.
...
The industry standard for evaluating helmet effectiveness involves measuring only the three translational degrees of freedom. By continuing to suggest the strong connection between the rotational forces and incidence of injury, the Stanford group hopes it can influence industry to apply rotational tests to evaluate existing gear, or to even design helmets that minimize rotational effects.
January 6th, 2015 at 2:52 PM ^
Now that is advanced athletic training research at it's finest!
January 6th, 2015 at 2:53 PM ^
Awesome share!
January 6th, 2015 at 2:54 PM ^
January 6th, 2015 at 3:59 PM ^
Measuring shear forces has been possible for a long time, but it's my guess based on my experience using load cells that the types of transducers available were inappropriate for kinesiology research or that it was not possible to correlate the shear force measurements to the theoretical values based on the physics.
I haven't tried to instrument a human skull (though I know someone who did for the purpose of studying TMJ) but I have to imagine that trying to figure out which cross sections of bone, brain and fluid were important and how to measure them was the crux of the issue. Finite element models of the human head have been available for several years, but the model would also have to take into account nonlinear forces that were time-dependent, as well as nonlinearities with the head, its materials, and how they both respond under load.
January 6th, 2015 at 4:12 PM ^
Since you seem to be knowledgble in this area, I can see how linear forces can be cushioned. Any ideas how you deal with cushioning rotational forces as they would seem much more difficult to attenuate than linear force.
January 6th, 2015 at 5:02 PM ^
I'd have to think about it a while, but the right answer may be more than just trying to cushion the blow. One of the safety innovations in race car design over the past couple of decades (and now used to some degree in normal passenger cars) are components that are designed to take impact loads and yield under the stress, directing the energy away from the human occupants. If you've seen crashes at the track, you'll see all kinds of bits of the cars flying everywhere. In most cases, those parts are designed to do that.
Similarly, automotive engine mounts in modern passenger cars are designed to yield so that the energy is directed away from the passenger compartment (usually down). In the process, the vehicle is essentially destroyed but the passengers escape with comparatively minor injuries if any.
Football helmets and other protective gear could be similarly designed. Ironically, one of the events that causes a player to automatically sit out at least one play is when the helmet comes off. While that leaves the head exposed for the time it takes to complete the play, the energy required to lose the helmet may have done a lot to protect the player by reducing the loads on his head.
January 6th, 2015 at 5:24 PM ^
I follow racing, particularly F1, fanatically and I understand how car design has been used to dissipate energy away from the occupant, but you have an external object, the vehicle itself, that a football player doesn't have to dissipate force. A HANS device does a great job of limiting acceleration with a driver strapped tightly into a car, but it is in one direction only that the drivers brain is protected and that is forward (developed at MSU I am sorry to say).
Helmets have to be strong and lightweight enough to be able to sustain a blow without breaking apart. If football were a sport played with a single "hit", even a broken helment might be acceptable, but multiple impacts can occur, so helmet breakage as a means of energy disspation is not viable, or so it would seem, with most typical polymers used in helmet construction.
I read something not too long ago where woodpecker skulls were considered for helmet design due to the manner in which woodpeckers have high forces while pecking on trees, but that would be linear, not rotational forces.
January 6th, 2015 at 5:40 PM ^
Having the helmet literally break as a result of a hit probably wouldn't be a good idea, obviously. That would make them similar to the bumpers on cars, which are designed to withstand, basically, a single hit (and at low speed) without sustaining noticable exterior damage. However, even a collision at 5 MPH typically deforms the foam behind the bumper's outer shell, reducing its effectiveness in future collisions. It's one of the reasons that most manufacturers recommend an inspection following a collision regardless of speed.
January 6th, 2015 at 4:12 PM ^
January 6th, 2015 at 4:12 PM ^
January 6th, 2015 at 4:50 PM ^
But living tissue responds differently under load than dead tissue. I haven't read the research or textbooks to know why that happens, but I suspect it's due to the electrochemical responses and controls of the brain that affect the rigidity of tissue.
Also, it's been pretty widely understood for a while that awareness of pending impact causes the body to both consciously and unconsciously prepare. All of those factors together would make it difficult to use cadavers alone.
January 6th, 2015 at 8:49 PM ^
Sorry for the bad grammar, i am not a native english speaker.
I have done some research (pretty much reading papers) in this area, so know a little about this, I am by no mean an expert on this field though. Based on the papers i read, the biggest challenge of detecting concussion is its complexity. While researches show that shear forces may play an important role, sometimes more important than linear force. The brain itself isn't a solid body, so during the impact, the kinetics of the brain moving relative to the skull is very complex, and groups in different universities such as Wayne state, Wisconsin, and many others have tried to develop brain/skull finite element model, I think in the future, as the biomechanic models are better, we can probably simulate how the brain move due to the impact. Keep in mind that in some rare cases, as I read through stanford group's previous articles, hitting the chest or upper body can cause the spine and neck to bend, while the head was accelerated from a still position, that can cause concussion too. I think the unknown cause of concussion make it a challenge to come up with a guideline or an engineering way to detect it.
As far as impact measurements, there are a few points i want to make.
1) mouth guard may not be the best instrument, because the assumption is the mouth guard is mechanically couple with the skull, through your teeth. But sometimes, the mouth guard can fly away in abmormal cases. Similarly, sensors installed on a helmet is also not reliable, either. My guess is that the a mouth guard could couple with the skull better than a helmet though, and more reliable, but not perfect.
2) To my knowledge, a more precise explation for the cause of concussion in terms of "shear" is the shear strain of the brain tissues. The shear forces calculated from tortional or linear impacts detected from the skull via helmet or mouth guard, or any other insturment attached to the skull, may not be easily converted to the shear strain of the tissues. biomechanic modeling the skuls as well as brain tissues probably can solve this problem, but the research si still on going. There are a lot to be done in this area.
Overall, the cause of the concussion is not well known, and there were limited instruments and technologies to detect the impacts in the past. Research of linear impact has been going on for tens of years in automobile indusstry. But the kinetics of the human body and skull/brain is more complicated in sports compared to a car crash. The complexity of how the head and brain move make this reasearch more chanlleging.
January 6th, 2015 at 3:03 PM ^
Good, the more research we have on this the better
January 6th, 2015 at 3:33 PM ^
Gotta love Stanford
January 6th, 2015 at 3:35 PM ^
This is good- I wonder if helmet hits and slaps can be banned altogether. It wouldn't change the game and these hits have to add up. I also think players need more neck cushions to stop a hemet whiplash during a fall. You don't see neck cushions much in college.
One of the big problems is that high schools don't spend much on helmets and many of these offer little protection. Most serious injuries are in high school.
January 6th, 2015 at 3:39 PM ^
I've always wondered why people still slap and butt helmets together. It has been shown that helmets colliding in the trenches with O/Dlinemen cause graded concussions that can have bigger problems in the long run than that of "classical" concussions. You would think this behavior would be discouraged in celebratory events.
January 6th, 2015 at 3:59 PM ^
When you butt helmets in celebration, you have the illusion of control. You are ready for the impact and don't feel any ill effects. Sadly, a lot of concussion and sub-concussion research seems to indicate that athletes can't perceive the damage from many of the impacts they sustain.
I think the game is going to undergo some major changes in the next ten years. The people who complain the most will be those who never sustain any impacts more serious than a bag of potato chips falling out of the cupboard and hitting their head.
January 6th, 2015 at 4:17 PM ^
you think the changes will be? Just curious. I mean, they can only make so many "changes" before it really becomes an entirely different sport. Targeting is a penalty, typically an ejection. I believe defenseless receiver penalties have also come to college, or at least will very soon. Technology and equipment has made drastic strides in terms of providing the most protection possible. Aside from paying college players and guaranteeing medical coverage and/or compensation for head injuries sustained, what "on the field" changes can really be made? I mean, you can't have boxing without punching, you can't have football without hitting. You can train players to use better technique but can you really implement the equivalent of "seatbelt laws" that penalize players for not properly protecting themselves? Aside from declaring the sport illegal, I don't know what major changes can really be made.
At some point the sport just becomes an open and obvious hazard and players play at their own risk. How many times can you say "yeah this can and probably will happen to you if you play" before it is just on the player to make the decision?
January 6th, 2015 at 4:20 PM ^
Get rid of helmets altogether. You won't see many head-to-head collisions, and the violence of the game will reduce drastically. You have to go one direction or the other--either padding that dramatically reduces these risks (doubtful that will be found soon), or else remove the padding and allow the players' natural self-preservation kick in.
January 6th, 2015 at 4:42 PM ^
Carroll teaches a whole new to NFL rugby style tackling for the Seahawks.
https://www.youtube.com/watch?v=7HihjPApzCg
January 6th, 2015 at 4:18 PM ^
You can only change the game so much before you make it unwatchable. Look at what the NCAA and NFL have done with kickoffs....and largely eliminated a very fun part of the game.
January 6th, 2015 at 3:50 PM ^
just released a statement saying that Michigan will soon research this matter in even more detail.
The guy is just intense.
January 6th, 2015 at 4:24 PM ^
...who can explain and/or mock-up a potential helmet design?
Also, I've always wondered why helmets had a hard outer shell instead of a thick memory-foam type material. Players use the helmet as a weapon b/c it's the hardest piece of equipment. Back in the 40s and before, when the helmets were leather, no one lead with the head. They might have ducked while going forward to keep their face from getting smashed, but they weren't trying to head-butt people.
January 6th, 2015 at 6:32 PM ^
January 6th, 2015 at 4:20 PM ^
People were coached to put their head on the ball to knock it loose.
January 6th, 2015 at 4:26 PM ^
Coaching point: bite the ball.
January 6th, 2015 at 6:59 PM ^
I was taught to tackle by putting my facemask/helmet-crown in the ball carrier's chest, driving through, and wrapping up behind the carrier's legs with my arms.
In 1975, leading with the head became a penalty, and we had to lead with a shoulder instead. It was called meticulously at first, but as I got older, the emphasis faded away. Maybe that was just a function of aging out of little league.
January 6th, 2015 at 10:12 PM ^
I was not alive during the time so I have no clue. Even when I began playing football in 5th grade I was told to tackle with my head up, throwing essentially double uppercuts, driving the legs and wrapping up. As I got older and moved on to more competitive football the technique varied slightly but the principle remained the same.
Did it used to be common for one to be taught to tackle with their head facing down but on the ball?
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January 6th, 2015 at 5:03 PM ^
Putting deformable shock absorbers on the outside of hard shell helmets is a no-brainer. The harder problem is people have to be willing to wear them in games as well as in practices in order to prove they're effective. And to be ethical, that kind of human trial can only be done with uncoerced volunteers.
January 6th, 2015 at 10:06 PM ^
The one thing we cannot change is the movement of the brain inside the cranium. As long as it is pin balling back and forth no preventative measure will ever be able to completely eliminate the potential for cranial injury.
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January 6th, 2015 at 5:04 PM ^
Good stuff. Rotational impact damage prevention technology is starting to come out for mtn bike helmets, hopefully it'll hit football helmets soon -- http://www.bikemag.com/gear/news-giro-releases-new-helmets-equipped-mip…
January 6th, 2015 at 7:41 PM ^
People were coached to put their head on the ball to knock it loose. - this is true!
January 12th, 2015 at 6:56 AM ^
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