Bicycle helmets do an outstanding job of keeping our skulls intact in a major crash, but they do almost nothing to prevent concussions and other significant brain injuries. The time has come to demand something safer
By Bruce Barcott
About a year ago my 14-year-old daughter needed a new bicycle helmet. Her skull and level of sophistication had both outgrown her old pink flowery one. We paid a visit to the local bike shop. On a far wall our options were stacked five high and 10 wide: multi-vented Specialized models, slick red and black designs by Giro, brightly coloured versions manufactured by Bell. There seemed to be little rhyme or reason to the prices, which ranged from a little to a lot.
“Do any of these provide better protection than the others?” I asked the guy working the floor. “Does price reflect safety?”
I trust the guy working the floor. Over the years he’s sold me tubes, tyres, lube, shoes, gloves. He knows his merchandise.
“Not really,” he said. “They all pass the same certification test.” The difference, he told us, is in style, fit, comfort, and ventilation.
That struck me as odd. We live in an age of near-comical product differentiation. You can buy cough mixture in 14 formulas, coffee in dozens of permutations. Yet when it comes to bike helmets, I later learned, we’re all wearing decorative versions of the same Model T: a thick foam liner (actually expanded polystyrene, or EPS) attached to a thin plastic outer shell. The basic setup hasn’t changed much since the first one was sold in 1975.
That classic design deserves serious plaudits. The affordable bike helmet is one of the great success stories of the past half-century. Like seat belts, air bags and smoke detectors, bike helmets save countless lives every year. They do a stellar job of preventing catastrophic skull fractures, plus dings and scrapes from low-hanging tree branches and other common nuisances.
But what about concussions? A friend of mine, Sheilagh Griffin, commutes on her bike and races on weekends. In a recent race she had lost control and flown over the bar. Though wearing a helmet, headaches plagued her for the next few days. Her doctor diagnosed a concussion. Twenty years ago that wasn’t such a big deal. It was a shake-it-off -injury. You popped two aspirin and saddled up again the next day.
That has changed. Sheilagh’s doctor told her to stop racing until the headaches subsided. And then sit out for one or two more weeks, to decrease the odds of a vastly more problematic second concussion.
This is because recent studies of professional sportsmen in contact sports have raised alarming questions about the disabling short- and long-term effects of concussions. Cycling isn’t immune from that conversation, at any level. Riders fall. Sometimes they hit their heads. In 2011, Belgian star Tom Boonen abandoned the Tour de France after suffering a crash-related concussion in the fifth stage. A few days later a concussion ended the race of Chris Horner, then the reigning Tour of California champion. More than a year on, Horner says he remembers nothing of the incident.
Standing in the shop, my thoughts turned to my daughter’s precious brain. Most of us reflexively strap on helmets assuming they’ll protect us. But how well do they actually do the job? I wanted to know if the technology and design of the headwear had kept up with our growing understanding of what goes on inside our skulls. I started asking questions.
Over the past year I toured helmet labs, interviewed brain researchers and US government regulators, and pored over dusty volumes in medical archives.
What I found was troubling.
To understand the present-day science of head protection, I visited the global epicentre of helmet design. It’s tucked away in an office building in Scotts Valley, California. The engineers and designers there call it the Dome because that’s what they’re paid to protect: the head, the skull, the cranium. The dome.
The facility was the brainchild of executives at Easton-Bell Sports. A few years ago the athletic-equipment company brought engineers, designers, lab technicians and product managers from its helmet brands – Giro (bicycle and snow sports), Bell (bike, snow sports and motorcycle), Riddell (gridiron), and Easton (baseball, hockey, lacrosse) – together under one roof. Result: a Wonka factory of head protection.
Eric Horton, creative director with Giro, guided me through the Dome. We walked past a dozen industrial designers working out new prototypes in low-walled cubicles. Over here, a cycling time-trial shell. There, an engineer digitally sketched an idea for a new BMX lid.
Horton soon led me into a mechanical symphony: the whump-whump pump of pistons stress-testing handlebars, the snap and crack of helmets shattering. I watched a technician strap a snowboard helmet onto a metal headform, raise it six feet, and drop it onto a steel plate. The impact had a surprising effect on me. Even with no human attached, it was a sickening thud.
It’s a sound Thom Parks has heard thousands of times. Parks is vice president for corporate affairs; he’s considered one of the wise old heads around the Dome. He’s been in the bike industry since 1973. He began working on lids at Specialized in the late ’80s and ran the company’s helmet division prior to joining Easton-Bell. He walked me through Helmets 101 – how they’re designed, constructed, tested and sold. I asked him why the industry still worked with EPS and plastic liners, which have been around for decades.
“We’re always looking (for something new)”, he replied. “That’s the holy grail, to find that miracle material. We have projects going right now. Different materials, different blends.”
Helmet companies have found it tough to top the reliability of EPS, which molds easily and provides the same impact response, helmet after helmet. Other substances can vary from batch to batch. “A lot of people come to us with great ideas,” said Parks. “Sometimes we’ll spend crazy amounts of money pursuing new materials. We had a project that came out of Europe a few years ago. We spent hundreds of thousands of dollars trying to make it work. It was close. But it didn’t work. In the end it’s got to have a real-world advantage. And it has to work in the testing lab.”
Standards set by the US Consumer Product Safety Commission (CPSC) demand that helmets perform – that is, hold up through the six-foot drop test – at room temperature and in a variety of extreme conditions. Lids are tested at temperatures as high as 52°C and as low as -17°C, and after being immersed in water for at least four hours. As years passed, liner materials came along that might have protected the brain better than EPS, especially in common, everyday-type weather. But none could survive the CPSC’s extreme environments.
We turned to the subject of concussions. Parks said his design team follows current brain research. “And we’re always asking, ‘Is there some aspect of their learning that can be reflected in the headgear?’
“The issue’s huge,” he added. “We know helmets have done a pretty good job of dealing with significant test-lab impacts. But we’re also asking the question: while still meeting high-impact standards, can we design a structure that also works well with low-energy impacts?” In other words, helmets are great at softening rare catastrophic blows. But what about more common crashes, the ones that happen at slower speeds but can still result in concussion? Testing those lesser blows, Parks and Horton said, might be as simple as dropping the headform from three feet instead of six. Engineers in the Dome already do a fair amount of that, though it’s not required, and Parks is among those pushing to make a low-drop-height test mandatory for bike helmets. Designing a helmet to offer both kinds of protection, however, isn’t as easy as you might think.
A bike helmet is designed to spread the energy of an impact over space and time. The outer shell works like a shield for the skull and distributes the blow across a larger surface area. By crushing and cracking, the inner EPS liner attenuates impact energy – that is, it extends the hit over a longer period of time. Six milliseconds, say, instead of two. Helmet experts call it “slowing the blow,” and it can turn a lethal fall into a survivable one.
The problem? EPS doesn’t absorb much energy unless the impact is forceful enough to make it start to disintegrate. “Think of it like a glass,” Parks said. “If you hit it lightly it won’t deform at all. But hit it hard enough and it will shatter. It’s not really attenuating any impact energy until it starts deforming and cracking.”
A helmet that deforms more easily might better protect the brain against smaller falls. But it could also lessen the helmet’s catastrophic-impact protection.
The state of my friend Sheilagh’s helmet illustrated the problem. “The helmet doesn’t appear damaged at all,” she said. “There’s a little dent in the front of the shell, and another one on the back right side.”
Those marks indicate that the helmet protected her skull. But the liner remained intact. That means a significant portion of the impact energy was absorbed not by the helmet, but by her brain.
During our talk the Giro designers rolled out their pride and joy, a radical new helmet called the Air Attack. Unlike today’s vent-crazy designs, it features a closed-cap construction, with only four small vents.
Mark Cavendish helped to cement the design idea. At the UCI Road World Championships in September 2011, he clapped a rain shield over his vented helmet and beat the field. Whether he actually gained an aero advantage over his competitors – the day was dry – is arguable. But Cavendish’s brash move affirmed Giro’s plans for a ventless aerodynamic helmet already underway. Months of sketches, wind-tunnel work and safety testing went into the design.
Rabobank and Garmin-Sharp riders adopted the Air Attack during last year’s Tour de France. Subsequently, road-bike websites had lit up with gearheads lusting after the helmet. The Air Attack perfectly illustrates what drives most helmet innovation: performance. For decades, major helmet manufacturers have competed on styling, comfort and aerodynamics. Not safety.
After my visit to the Dome I spoke with numerous current and former helmet designers. Many said the same thing. “A lot of the innovation in helmets has been focused on making them lighter, more ventilated and fit better,” said John Thompson, bike helmet product manager for Scott Sports. “The customers leave it to the certifying authority to assure safety.”
When helmet certification first began over 60 years ago (see below), the medical world thought the brain was a solid organ encased in a hard shell. Severe injuries, it was believed, were caused primarily by the brain rattling against its casing like dice in a box.
Research has since disproved that notion. The brain’s grey matter of closely packed neurons (cells that transmit information through electrical and chemical signals) in fact more closely resembles tofu. Those cells communicate via nerve fibres called axons.
If you crash and hit your head, there are two types of impacts. One is known as linear acceleration. That’s the impact of skull meeting pavement. Today’s helmets do an excellent job of preventing catastrophic injury and death by attenuating that blow.
The second type is known as rotational acceleration. This is where things get tricky. Even if the skull isn’t damaged, it still stops short. That causes the brain to rotate – the technical term is inertial spin – which creates shear strain. Imagine a plate of fruit jelly being jarred so hard that little cuts open throughout the jiggly mass. That strain can damage the axons that carry information between neurons.
There are other factors involved, but research has consistently pointed to rotational acceleration as the biggest single factor in a concussion’s severity. The CPSC helmet benchmark is based solely on linear acceleration. There’s never been a standards test, required or voluntary, for rotational acceleration.
That disconnect made me wonder. Surely the link between rotational acceleration and concussions must be a recent discovery. To find out, I dug into the University of Washington’s health-sciences library. Following a trail of footnotes, I traced the connection back as far as it would go.
It went a long way. In 1962, a team of Michigan State University researchers presented a study at the American College of Sports Medicine’s annual convention. “It is fairly well established that the extent of skull fracture and severity of concussion are not closely related,” they said. Further research, they added, should focus on “developing headgear which would provide greater protection from brain concussion.” A decade later, National Institutes of Health (NIH) scientists warned that “existing helmets are not protecting the brain adequately” because their design was based on a paradigm that ignored data on rotational forces. Revising the existing standards was deemed an “urgent task.”
The most interesting studies involved, of all things, woodpeckers. In the 1970s, researchers at the University of California at Los Angeles wondered how the birds could rat-a-tat all day long without hurting their brains. Their beaks hit with a force of more than 150G. Why wasn’t the forest littered with dazed birds?
Using high-speed film, the UCLA team discovered the woodpecker struck the tree on a perfectly linear trajectory. Between strikes, its glide path forward and back was dead level, which resulted in almost zero head rotation. Woodpeckers, the researchers theorised, sacrificed the greater power they’d get from swinging their beaks in an arc – like hitting a nail with a hammer – for the brain-protecting value of a straight-line strike.
In light of previous studies, this led the UCLA researchers to ask the medical community to “discard the magical notion that wearing a helmet on the head is sufficient to protect against impact brain damage.”
During that same era, NIH researchers working with monkeys found it impossible to concuss the primates using straight linear acceleration. Meanwhile, every instance of rotational acceleration resulted in concussion. (No question, head-trauma research in those days was gruesome and ethically questionable.)
Further studies in the ’80s, ’90s and 2000s linked rotational acceleration to concussions and other brain injuries. But without a standard addressing this phenomenon, helmet manufacturers haven’t been forced to adapt their products. A report last year by the International Olympic Committee World Conference on Prevention of Injury and Illness in Sport summed up the state of the art in a sentence: “Little has changed in helmet-safety design during the past 30 years.”
In their defence, manufacturers and researchers say they don’t have enough information. “We don’t know where to set the injury threshold,” David Thom told me. That is, there’s no set number above which concussion occurs. “That’s an area of intense scientific interest right now,” he said. “So far nobody’s got a standard. We haven’t even got agreed-upon test equipment.”
That’s true, up to a point. Researchers have measured rotational acceleration in headforms for decades. The equipment exists.
It’s partially a chicken-and-egg problem: there’s no agreed-upon test because the major manufacturers haven’t yet developed a helmet that dampens rotational acceleration. If nobody invents a concussion-reducing helmet, there’s no reason to agree upon the standard
for testing it.
Some in the industry contend that helmets should not, or cannot, prevent concussions. Snell Foundation executive director Ed Becker, a respected member of the ASTM (American Society for Testing and Materials) helmet subcommittee, told me that Snell helmet standards have always focused on catastrophic impacts. “We haven’t really worried about concussion,” he said. “We’re mostly worried about the single impact that doesn’t just concuss but leaves a rider with long-term disability or kills him outright.”
Dave Halstead, ASTM helmet chairman, remains staunchly unconvinced that a new helmet design might significantly reduce concussion risk. “A lot of people think that because people sometimes suffer concussions while wearing helmets, that the helmet didn’t do its job,” he said.
He believes that, in fact, the problem lies in the way the head is attached to the body. When a rider falls, he said, “the head rotates like the end of a flyswatter, and the shear strain is high enough to break axons in the brain.” The only solution, Halstead contended, would be to outfit cyclists with something like the HANS device in racing cars, which uses straps to prevent whiplash. “The likelihood of preventing concussions with a better helmet,” Halstead said, “is almost zero.”
Others disagree. Over the past decade researchers and engineers have ardently worked on the the problem, ranging from a biomedical engineer in Florida to a well-financed group of inventors associated with Sweden’s Karolinska Institute, one of Europe’s most prestigious medical universities. There’s a striking commonality, though. With one exception, they all come at the problem from a medical perspective.
They believe a better helmet can help prevent concussions. Not all concussions. Some of them. And they believe they have the data to prove it.
In the late 1990s a Swedish neurosurgeon named Hans Von Holst grew weary of seeing helmet-wearing patients who’d suffered brain injuries in bicycle and equestrian accidents. In most cases, the damage had been caused by rotational acceleration. Working with Peter Halldin, a mechanical engineer at Stockholm’s Royal Institute of Technology, Von Holst noted that the head has a built-in protection system of sorts – a low-friction layer of cerebrospinal fluid between the brain and the skull. The fluid allows the brain to move a bit; it acts as an energy-absorbing system. Von Holst and Halldin hatched an idea: what if they mimicked that action within a helmet?
That wasn’t their only insight. Since the 1950s the drop test has been based on a straight 90-degree impact. But pile-driver drops occur only in professional wrestling and Warner Bros. cartoons. Studies show that most bike falls result in an impact angle between 30 and 45 degrees. The Swedish team invented a test rig that examined drops at those more realistic angles.
By 2008, they had a working model. Their MIPS (Multi-directional Impact Protection System) helmet contained a low-friction slip plate between the head and EPS liner. On impact, the helmet rotates independent of the MIPS liner, absorbing some rotational acceleration.
Their tests indicated this made a difference. Rotational acceleration is measured in radians per second squared, or rad/s². According to tests done by the independent lab Biokinetics and Associates, riders wearing conventional bike helmets suffered a 7,000 to 11,000 rad/s² brain spin during crashes. (The discrepancy was due to different head positions at impact.) The MIPS helmet brought those numbers down to 6,000 to 8,000 rad/s² – which doesn’t eliminate concussion risk, but rather reduces it. The technology also reduced linear impact by 10 to 20 percent.
Those are significant numbers. The science isn’t perfect on concussions, but in 2004, Wayne State University researchers for the first time pegged risk of concussion to rad/s² data. By replicating the speed and angle of NFL collisions on video, and correlating each hit to the known medical outcome, the researchers found that players had an 80 percent probability of getting a concussion when the collision produced a 7,900 rad/s² spin. At 5,900 rad/s² the odds dropped to 50 percent and 4,600 rad/s² resulted in a concussion only 25 percent of the time. So bringing rotational acceleration down by a couple thousand rad/s² – to where spin is below the threshold for an almost certain concussion – is a big deal.
As the MIPS engineers finetuned their system, a group of inventors in Portland, Oregon, also attacked the problem. Steven Madey is an orthopedic surgeon. Michael Bottlang is a biomedical engineer. The two men have collaborated for more than 15 years. Their Legacy Biomechanics Laboratory is the kind of place where saws, clamps and chisels hang next to complete human skeletons. They have a proven track record in the field of medical innovation. First responders in 46 countries use their SAM Pelvic Sling to stabilise hip-fracture victims at accident scenes.
They brainstormed the problem. “The question became, what does a conventional helmet do to prevent acceleration of the brain?” Bottlang said.
To get a rough idea of the rotational forces that impact an unprotected head, Legacy Biomechanics biomedical engineer Nate Dau looked to a study done by Wayne State researchers. (This university, in the Detroit area, is a leader in body- and head-impact research because of the field’s importance to car-safety design.) In 2007, scientists there dropped eight human cadaver heads at a speed of 11km/h and measured each brain’s rotational acceleration. They averaged about 10,600 rad/s². The standard helmet-drop test happens at twice that velocity. Those forces don’t lend themselves to linear extrapolation, but it’s safe to say the spin on the brain in a naked head would be well north of 11,000 rad/s².
Using a slightly different testing method than his Swedish counterparts, Dau found that conventional helmets lowered the spin to 9,400 rad/s². (The difference between the Portland and Stockholm data lends credence to David Thom’s point about the lack of a uniform standard.) Bottlang and Madey figured they needed a helmet that was capable of absorbing both linear and rotational energy – something that might approximate a crumple zone in a car.
After years of experimenting with different materials, Bottlang and Madey hit upon a potential solution: they built an aluminium honeycomb liner with ultra-thin cell walls that replaces the EPS liner. The liner isn’t static; it floats slightly between the head and the helmet’s hard outer shell. A thin polymer sheath rides between the aluminium liner and the head. During impact, the liner shifts to absorb some rotational energy; the honeycomb cells buckle individually to absorb impact energy.
When Dau strapped the prototype AIM (Angular Impact Mitigation) helmet onto a headform, the data came back strong. Spin ranged from 3,400 to 6,200 rad/s². Compared with a conventional helmet, the AIM design lowered the likelihood of concussion from greater than 80 percent to about 50 percent in the worst case, and lower in other crashes. Dau’s data didn’t predict a concussion-proof helmet – but the numbers indicated the AIM design might be a solid step forward.
How did these innovations go over within the helmet industry? They made scarcely a ripple.
The MIPS team, thinking they’d revolutionised helmet safety, shopped their prototypes with a view to licensing the technology. Few brands were interested.
“Helmet companies had been programmed only to pass US or EU certification,” Niklas Steenberg, CEO of MIPS, told me. (The European Union has a helmet standard that is slightly different than the US version.) “We’d created a situation where good protection was available but no-one gave a damn about it because you didn’t need it to pass certification.”
That helmets weren’t protecting the brain against concussion, Steenberg said, “wasn’t even on the agenda.”
Back in 2008, most people were only beginning to grasp the seriousness of concussions. And there’s more nuance here than a frustrated Steenberg conveyed. Big helmet makers devoting enormous time and expense to their products can’t easily adapt a radical new technology. Easton-Bell and other big companies were starting to make early R&D forays into the issue – but behind closed doors, away from the eyes of competitors.
Most helmet designers and marketers are avid cyclists. They value their brains and those of their customers. But their customers – from top pros to weekenders – haven’t been clamouring for safer helmets, and the unchanging standards helped to ensure they were never offered one. And the industry’s independent safety experts have for years insisted that no helmet can reduce concussion risk.
When the MIPS system appeared, those experts dismissed it. “That’s not doing anything except taking up space,” Dave Halstead told me. “It’s a wonderful solution for a problem that does not exist.”
Randy Swart, the ASTM helmet subcommittee’s co-vice chairman, said he found the MIPS data “just not compelling.” He called MIPS “an unproven technology. I think it just adds complexity – and could add to the thickness of the helmets.”
In some cases, these assumptions were not true. The MIPS system doesn’t make helmets larger or heavier. The idea that the only safer helmet is a bigger helmet has been accepted for so long that it’s become an ingrained assumption.
As he hopscotched across Europe and the States, MIPS chief executive Niklas Steenberg found himself giving product pitches that sounded more like neurological seminars. Eventually his message began reaching receptive ears. An equestrian gear company introduced a MIPS-equipped helmet in 2009. The Swedish gear maker POC introduced the first MIPS mountain bike helmet in 2011. That year, snow-sports equipment manufacturer Burton signed on as well.
It took Steenberg more than four years to convince Scott Sports to take a chance on the system. John Thompson, the company’s bike-helmet product manager, first talked with the MIPS team about three years ago. “We noticed when it crept into the equestrian market,” Thompson says. The more he looked into it, the more he believed all helmets need concussion-dampening systems. But it wasn’t an easy call.
Thompson sees his challenge as story and price. He has to convince customers that a MIPS-equipped helmet is safer, despite the fact that all helmets pass the same safety test.
Back in the Dome, the quest for new designs has been a hot topic. Thom Parks and five Easton-Bell colleagues last year attended a symposium on concussions organised by the ASTM’s helmet subcommittee. The company has intensified its research efforts in that area, assigning a team to focus specifically on innovative head protection.
As the market leader in the US, Easton-Bell isn’t as nimble as a smaller company, but it can marshal great resources. Cyclists can expect something big from the Dome within two to three years, Parks said, but he declined to offer specifics: “Our projects are proprietary, so we can’t speak to what’s in our innovation pipeline.” But he reiterated that any new technology must confer a real-world advantage that’s proven in a laboratory. Similar initiatives have already bubbled to the surface from the folks in the Dome. Giro recently unveiled the Combyn, a snow-sports helmet that contains three different densities of vinyl nitrile (VN), an impact-absorbing liner material more commonly found in football and hockey helmets. Giro engineer Rob Wesson indicated that the poly-density VN design “could someday prove useful for bicycling helmet liners,” but company officials were leery of saying more. The helmet landscape is so riddled with legal landmines, in fact, that Giro can’t even advertise that the Combyn’s VN liner is designed and tested to withstand multiple impacts. It’s a tough spot: even when the Dome engineers advance the technology, legal constraints prevent the company from heralding their work as a safety innovation – reinforcing the idea that safety doesn’t sell.
There may never be an improved US government standard for bicycle helmets. Experts may never reach consensus on a standard for testing the forces associated with concussions. But one test does exist now: the market test. After all, new technology costs more. “Adding that upcharge to a $50 helmet,” Scott designer John Thompson told me, “is a harder sell.”
This is the bike-helmet industry’s air-bag moment. The new rotation-dampening systems may not be perfect, but they are the biggest step forward in decades. The choices cyclists make with their money matter. You can pretend to protect your brain, or you can spend more money and get closer to actually doing it.
Back in my local bike shop, my daughter eventually found a pretty and perfectly fitting sky-blue helmet. She went home happy – and for that day, at least, I was content with her choice. Now? Not so much.
A year later, I’ve replaced all four of my family’s snowboard helmets with MIPS-equipped models. The wait for something new we can wear during bike rides is frustrating. Every time I catch a glimpse of my daughter pedalling by, I think about her amazing, priceless brain, and I swear that her lovely blue lid will be the last one of its kind I’ll ever buy.
The History of Helmet Tests
1972
Snell Foundation in US issues first standard for ‘bicyclist’ helmets.
1984
American National Standards Institute (ANSI) issues benchmark for bike helmets. Revised Snell and American Society for Testing and Materials (ASTM) standards follow.
1990
Australian standard introduced, called 2063, one part for cycling, one for equestrian.
1996
Australian bike helmet standard, 2063 made official.
1999
The US Consumer Product Safety Commission (CPSC) standard mandated, combining Snell, ASTM and ANSI standards.
2008/9
Australian standard updated with dynamic retention testing and changes to drop height test requirements.
Hard Knocks
Anatomy of a concussion
If you fall off your bike and your head hits the ground, your skull absorbs energy from the impact. Wearing a helmet helps and the brain’s built-in shock absorbers soften the blow. But a hard enough hit will overcome those mechanisms, causing an injury such as a concussion. Because much of the damage occurs at a cellular level, concussions can be tricky to diagnose; even with advanced scanning technology, this kind of trauma is hard for doctors to see. But if they could peer inside a recently injured cranium, this is what they might observe. – Brooke Borel
Taking a spin
The head doesn’t sustain injury from just the direct collision with the road. The brain also has to contend with rotational acceleration (indicated by the long orange arrow at left), the shifting action that occurs as the head whips back on the neck. It can result in what’s known as shear strain, in which the brain tissue bends or twists. Imagine jerking a plate of jelly quickly so it separates, says Liying Zhang, research professor in the biomedical engineering department at Wayne State University.
What’s the matter?
The brain is made up of tens of billions of neurons – the cells that process information and send the messages that allow us to think and react to the world. The organ has long been described as being composed of “grey matter” but in fact, there is a second kind of tissue: white matter, comprised mostly of axons, the stringy messengers that connect the neurons, allowing the cells to “talk”. Because they have different characteristics and consistencies, the two types of tissue react differently to the forces that come into play when a head hits the ground.
Communication breakdown
Zhang and other scientists are still trying to unravel which of the brain deformations that occur in a crash cause which injuries. It’s possible that during a concussion some of the long axons may get sheared like a yanked strand of cooked spaghetti breaking in two, disrupting their signals (below). Or cell membranes may rupture as the axons are stretched apart, causing chemicals that are important to neural communication to leak. This cellular damage may cascade across the brain, continuing for days after the injury occurs, and may cause the common and often gradually morphing symptoms of concussion.
Lose the Lid?
A loosely connected band of outside-the-box thinkers have coalesced around the contrarian viewpoint that we’d be better served skipping the headgear entirely. Some think helmets are too limited as a safety device, while others just believe it’s a bad idea to require people to wear them. Here’s a look at some of their arguments. – Julia Merz
They make drivers complacent
In 2006, Ian Walker, a psychologist at England’s University of Bath, used an ultrasonic sensor to measure the distance between his bike and 2,500 passing cars over the course of two months. Vehicles passed him on average 3.35 inches closer when he wore his helmet. Walker argued that drivers assume cyclists wearing helmets are more experienced and need less space.
They increase risky riding
Psychologists Aslak Fyhri and Ross Phillips from the Institute of Transport Economics in Oslo, Norway, published a study in January in which they tested the risk-compensation theory: if you trust your helmet to protect you, you’ll engage in riskier behaviour, like riding faster. The researchers found that cyclists accustomed to wearing helmets rode slower without them. (People unaccustomed to helmets didn’t ride any differently after buckling one on.)
They scare away riders
This one gets tricky: the Australian-based organisation Helmet Freedom contends that helmets are good, but helmet laws are not. Requiring riders to wear helmets discourages riding by making the sport seem dangerous, the argument goes. The organisation cites a survey conducted by University of Sydney professor Chris Rissel in which 23 percent of Sydney adults said they would ride more if helmets were optional.
They diminish bike-share usage
Similarly in the United States, public officials worry that tying a helmet requirement to a share program will tamp down participation – at a time when cities are expanding cycling initiatives. Mayor Michael Bloomberg recently rejected the idea of requiring lids for New York City’s soon-to-launch Citi Bike program (though he still encourages individuals to wear a helmet).