October 17, 2011 | 2
It’s football season, which means marching bands, cheerleaders, doing the wave, and crowds going wild when their favorite team scores — and also more than a few bone-crunching collisions between players, a substantial fraction of which will result in injury. One of the most common foot-ball related injuries? Concussion. And this, in turn, can lead to longer-term damage to the brain. (The New York Times has run several excellent articles on the topic.)
A concussion is not the same thing as a bruise on the brain. There’s usually no swelling or bleeding. A concussion occurs when the head accelerates too rapidly, and/or decelerates too suddenly, or is twisted or spun in some way. Symptoms include confusion, blurred vision, memory, loss and nausea — sometimes unconsciousness, but not always.
Sure, professional players are required to don safety gear, including protective helmets, but according to this article in Technology Review, a helmet can’t completely prevent concussions. Fortunately, this an issue that the NFL, among other organizations, is taking very seriously, with a new sideline concussion test for its players.
If we better understood how and why concussions occurred, perhaps we could design better helmets and protect the players. So over the last few years, researchers at Virginia Tech have been working with sensor-equipped helmets developed by a company called Simbex to better understand all the forces acting on the head during a real-time football game that could lead to concussion, or worse.
It’s called a Head Impact Telemetry System (HITS), and is basically a professional football helmet outfitted with accelerometers and a radio transmitter capable of ranging the length of a football field. If the helmet takes a hard hit, the sensors detect it, measure it, and transmit that data wirelessly to laptop computer on the sidelines.
That data can alert coaches, for instance, when their players take a particularly hard hit, so they know to watch for signs of concussion (it is not always immediately apparent). And the stored data can later be synchronized with a central database to learn more about these kinds of injuries.
For instance, depending on what position you play, you’ll experience different kinds of hits. If you’re a lineman, you get a lot of lower-impact frontal blows, while wide receivers might get hit less frequently, but those blows are far more intense. And apparently linebackers take hits with higher accelerations than linemen. It might be that one day, we’ll see position-specific helmet designs, based on the kinds of hits different players are most likely to endure.
Researchers at the University of North Carolina — headed by Kevin Guskiewisc, also a member of the NFL’s head, neck and spine committee — are also employing sensor-embedded helmets in the lab to test the various physical forces and effects of impact at work during a typical football tackle, for instance. And the high-tech equipment under consideration by the NFL now includes sensor-equipped mouth guards and earpieces as well.
See, helmets tend to shift upon impact, affecting the accuracy of any data gathered. That’s why both the UNC and Stanford University researchers are using mouthguards outfitted with impact sensors — courtesy of Seattle-based company X2Impact — to collect similar data among college football players, to determine (hopefully) what kinds of hits tend to cause concussions, and “whether there is a threshold of hits past which serious damage may occur.” Per Technology Review:
The devices have six sensors measuring linear and rotational forces. They transmit information wirelessly to a monitoring device on the sidelines. A proprietary algorithm estimates the forces felt by the brain based on what the mouthpiece records. Mack says the mouthpieces don’t shift around excessively during play because they are molded to a player’s mouth. When they do shift, the system recognizes this and corrects for the movements. The mouthpieces also contain sensors that indicate whether they are in contact with mouth tissue.
The Stanford data will be compared to the data gleaned from the various sensor-laden helmet studies and hopefully give scientists a better idea of the forces at work in this kind of football injury. Of course, there are those who are skeptical that either device can accurately predict a concussion during a football game, based on the force and duration of a given hit (or series of hits). The same Technology Review article quotes Robert Cantu of Boston University’s Center for the Study of Traumatic Encephalopathy to that effect, but Cantu also adds, “It’s hugely important to record the number of hits,” even if it isn’t possible to pinpoint the exact location and force of a given hit.
The Pecking Order
So technology is helping shed light on the problem. What about Mother Nature? Perhaps we can also learn something from the lowly woodpecker, as I explained in a blog post earlier this year. One of my more distinct childhood memories is of visiting my grandmother’s house in Lewiston, Maine, a small-ish (back then) town in the southern part of the state. It was a big clapboard house on a quiet street, on the edge of a large wooded area.
I wandered aimlessly in those woods one afternoon, pretending to be an explorer of some sort (as children do), until I stumbled onto a clearing and snapped out of my fantasy world, suddenly aware that (1) I had no idea where I was, and (2) it was eerily quiet. Quiet, except for an occasional rapid-fire tap-tap-tap echoing through the clearing from a nearby tree. I found myself wondering: Doesn’t all that pounding away at tree trunks give the woodpecker a headache? Because it looked like it should hurt. A lot.
Kids always ask the best, most basic questions; they haven’t learned yet to pretend to be smart, to be ashamed of their ignorance; they’re just curious about how the world works. And the best scientists ask those kinds of questions too, which is why we might roll our eyes and chuckle a bit when we read about two California scientists who decided to delve into the underlying science of why it is that woodpeckers don’t get headaches.
There’s more to it than an easy punchline. Ivan R. Schwab of UC-Davis and his late colleague, Philip May of UCLA, won the 2006 Ig Nobel Prize in Ornithology for their work, published in the Journal of Ornithology — and the Ig Nobels, as founder Marc Abraham would be the first to tell you, are designed to honor research that first makes you laugh, and then makes you think.
See, it’s not such a stupid question, especially since, during courtship, the male woodpecker can drum a good 12,000 times a day (normal rate is still an impressive 500-600 times a day, usually to forage for food). And those aren’t just light taps, either.
A woodpecker typically drums away at a rate of 18-22 times per second, with a “deceleration” force of 1200 g. (Recall from high school physics class that the more slowly you decelerate, the less the impact, because the energy is dissipated over a longer period of time. Sudden stops or sharp blows, therefore, can pack quite a wallop.) Humans, on the other hand, will lose consciousness under 4 to 6 g’s. and a sudden deceleration of 100 g will cause a concussion.
In February 2011 a new paper appeared in Bioinspiration and Biomimetics entitled, “A Mechanical Analysis of Woodpecker Drumming and Its Application to Shock-Absorbing Systems,” building on Schwab and May’s earlier research. Schwab and May’s study found that the key to protecting the pileated woodpecker from chronic headaches or more serious concussion had to do with the structure of their heads — “thick muscles, sponge-like bones, and a third inner eyelid,” all of which work together to absorb impact — and the fact that woodpeckers make straight, clean linear strikes. Per Live Science:
One millisecond before a strike comes across the bill, dense muscles in the neck contract and the bird closes its thick inner eyelid. Some of the force radiates down the neck muscles and protects the skull from a full blow. A compressible bone in the skull offers cushion, too. Meanwhile the bird’s closed eyelid shields the eye from any pieces of wood bouncing off the tree and holds the eyeball in place. “The eyelid acts like a seat belt and keeps the eye from literally popping out of the head,” Schwab [said]. “Otherwise acceleration would tear the retina.”
Okay, that’s interesting, you might be thinking, but what good is that insight? That’s where UC-Berkeley’s Sang-Hee Yoon and Sungmin Park come in. They’re the authors of the most recent paper, and they studied videos of woodpeckers in action, and also took CT scans of the bird’s head and neck (see image, above) to more clearly determine how it absorbs mechanical shock so well.
Specifically, the beak is both hard and elastic, there is an area of spongy shock-absorbing bone in the skull, and woodpeckers have another springy structure in back of the skull called a hyloid. The skull structure works in concert with cerebrospinal fluid to further suppress vibrations.
Yoon and Park then set about finding ways to artificially mimic these attributes in a manmade mechanical shock absorbing system, specifically to protect microelectronics components. Per New Scientist:
To mimic the beak’s deformation resistance, they use a cylindrical metal enclosure. The hyoid’s ability to distribute the mechanical loads is mimicked by a layer of rubber within that cylinder, and the skull/cerebrospinal fluid by an aluminum layer. The spongy bone’s vibration resistance is mimicked by closely packed 10-millimeter-diameter glass spheres, in which the fragile circuit sits. To test their system, Yoon and Park placed it inside a bullet and used an airgun to fire it at an aluminum wall.
It will also help protect, say, the electronics in airplane flight recorders, making it less likely that critical information will be damaged in the event of a crash. The scientists found that their mechanical shock-absorbing system reduced the failure rate of the microelectronics from 26.4% (using the conventional hard resin method) to 0.7%, despite the fact that the microelectronics suffered shock levels as high as 60,000 g.
Other applications being bandied about include using the shock absorber system in “bunker-busting bombs”, and to protect spacecraft from space debris (a growing problem, especially given our current reliance on orbiting satellites for communications).
It might even be useful in Formula One racing, protecting drivers from serious brain injury and internal damage suffered during the inevitable accidents.
Here’s another suggestion for a possible application: protecting football players from concussion. While several manufacturers of sports equipment tout the superior safety of their helmets, Mike Oliver, the executive director of the National Operating Committee on Sports Atheletic Equipment, told Technology Review that “we know from the test data that all the helmets [on the market] are nearly identical [in performance].”
How can this be? Think back to the lowly woodpecker and how it strikes the tree trunk with its beak in a straight, linear fashion. That’s key, because head injuries — in football and beyond — aren’t just the result of linear acceleration, but also too much torque, in which the head rotates or twists. According to Oliver, “The brain is very sensitive to torque, some scientists think this also causes tension between the brain and brain stem.”
The Human Factor
Here’s some alarming statistics: a 2000 study of NFL players found more than 60% suffered at least one concussion in their careers; 26% suffered three or more concussions. Those players also reported issues with memory, concentration, speech, and headaches.
And the damage extends beyond their active careers: a 2007 study examined nearly 600 retired NFL players who’d had three or more concussions in their careers, and found that 20% of them suffered from depression — three times the rate of players who had never suffered concussions.
Depression often leads to suicide, like in 2006, when former football player Andre Waters shot himself in the head. Postmortem analysis of his brain tissue showed signs of a degenerative disease called chronic traumatic encephalopathy, more commonly found in boxers (who are also highly prone to concussion).
And this year, the NFL community was stunned when former Chicago Bears star Dave Duerson shot himself in the chest, right after texting his ex-wife asking that his brain be donated to the NFL’s brain bank for further study. There may have been other contributing factors to Duerson’s tragic suicide — he was having personal and financial problems — but he also was experiencing worsening short-term memory loss, blurred vision, and chronic pain.
See? I told you it wasn’t a stupid question to ask why hummingbirds don’t get headaches. It’s easy to snicker at seemingly superfluous scientific research, but in this case, something as trivial as looking a bit more closely at a woodpecker could one day help stave off brain damage in NFL players. Maybe it’s too late for Dave Duerson, but it’s not too late for tomorrow’s gridiron stars.