Hits to the head: Scientists explain Sidney Crosby’s concussion

What crash-test analyses reveal about hits, helmets, and the game of hockey

The aftershocks

Neurotrauma impact lab: University of Ottawa scientists reconstruct hits to the head, including ones from pro hockey, to better understand concussions. Photographs By Blair Gable.

Inside a white cement-block science lab at the University of Ottawa, two young researchers cover a beige crash-test dummy head with a black nylon stocking. It’s supposed to mimic the tousled hair of Pittsburgh Penguins superstar Sidney Crosby, who’s been knocked out of the game since early January because of two massive, back-to-back blows to the head. Here, at the elite Neurotrauma Impact Science Laboratory, researchers led by Blaine Hoshizaki are reconstructing a hit similar to Crosby’s first one to establish the relationship between helmet performance and how concussions occur. That nylon stocking, however out of place it seems, makes sliding a helmet on and off the sticky urethane and aluminum head form easier.

Guided by a laser, they position the dummy inside a Plexiglas cage so that a thick metal rod with a hard, white plastic nib is aimed at its left side—precisely the spot where the cold shoulder of David Steckel of the Washington Capitals hit Crosby during a game on New Year’s Day. Everyone nearby in the hangar-like space puts on heavy-duty earphones and steps behind yellow and black danger tape on the floor. With one press of a red button, a calculated reconstruction of the hit similar to the now infamous Crosby-Steckel one is under way.

Beep! Beep! Beep! A shrill, pulsating tone precedes a bursting whoosh as an air compressor drives the rod into the head form at the exact same speed (27 km/h) and angle as when Steckel’s 217-lb. body collided with Crosby’s head. The crash hurls the head form along a monorail track while it flops back and forth on a dummy neck. However hard the hit looked on the ice, seeing it in the isolation of the lab is disturbing—much like the unsettling feeling one gets from watching footage of crash-test dummies flailing in car accident re-enactments. It’s the distinct surprise that anyone survives these events.

The aftershocks

David Denoma/Reuters

During the five-millisecond flash of impact, nine sensors inside the head form each pick up data at 20,000 times per second. That generates a 3-D computerized brain model depicting where brain tissue stress has occurred. Tissue stress reflects injury. Whereas a computerized image of an unaffected brain would be coloured all blue, the image representing a head side-swiped like Crosby’s shows a rainbow of stress emanating from the left hemisphere—green, yellow, orange, red, grey. There is hardly any blue on that side of the brain.

To Hoshizaki, director of the lab, the dramatic results are frustratingly similar to what he’s discovered in doing thousands of reconstructions of brain injuries, including many NHL and NFL concussions, over the last few years: that no matter what make or model of helmet Crosby was wearing, and no matter how much it met or exceeded safety standards, the current equipment isn’t built to protect players specifically from concussions. And, just as troubling, the rules of the game and the way players are managed don’t adequately help either. Hoshizaki wants to change that.

He and his team of young scientists who run this lab are in a good position to make that happen. No one else in the world is doing exactly this type and extent of research. To be sure, nowhere else in the world does it matter more than in a country whose undisputed sports hero has gone from bionic golden boy to one more broken pro athlete. Ever since Crosby’s last game on Jan. 5, when a crushing check into the boards by Victor Hedman of the Tampa Bay Lightning gave him a concussion that he’s still battling, hockey league officials and fans alike have been hand-wringing about how this could have happened to one of the greatest players since Wayne Gretzky—one who’d been on a 25-game scoring streak, a feat so amazing that it last happened nearly 20 years ago.

RELATED ARTICLE: The damage done by concussions—Sidney Crosby as a case study

Hoshizaki will have plenty of answers when, on Feb. 23, he speaks at the first-ever hockey safety summit devoted solely to concussions. The event has been in the works for almost a year and will be attended by representatives from the NHL, the American Hockey League, Hockey Canada, USA Hockey, as well as the standards organizations and minor and amateur leagues. As part of his presentation, Hoshizaki will be using the brain model from the reconstruction to demonstrate the disconnect that currently exists between what his lab indicates about hits to the head and what actually happens on the ice.

The summit will be hosted by Reebok-CCM, which has a $10-million deal with Crosby, the richest endorsement in NHL history. That this hockey icon is currently out of the game, says Olivier Camet, the company’s senior product manager, “makes it even more clear that we need to take this seriously and do everything we can to prevent concussions in the future.” The summit is all the more pressing given the recent admission by Crosby that he might not be back for the rest of the season because of the brain injury. “That could happen,” he conceded uncomfortably. “Am I sitting here packing it in? No, I hope I’m back, and geez, I hope I play this year. But that is the thing, you don’t know. There’s no time frame.”

The aftershocks

Neurotrauma Impact Science Laboratory/University of Ottawa

And there’s no certainty about what kind of player Crosby will be if the much-anticipated day comes when he takes to the ice for another game. The longer he’s out, the more troubling the situation, says Dr. Michael Cusimano, a neurosurgeon and researcher at St. Michael’s Hospital and a professor at the University of Toronto. Cusimano believes that Crosby’s biggest athletic asset is his brain and he worries about what this injury has done to it. “A player like Crosby can think of probably 10 different things at the same time as he’s holding the puck, and he’s analyzing the situation so precisely, that is what’s giving him the competitive edge,” says Cusimano, who is conducting a national study on concussion in the general population with Hoshizaki for the Canadian Institutes of Health Research. “It’s not that he has bigger muscles, or that he skates faster, or that his slapshot is faster, or that he can hit players better. The difference between him and [others] is his cognitive abilities.”

VIDEO: Hit to the head: a similar one to Sidney Crosby’s (reconstruction)

Assuming Crosby does play again, and fans, competitors and sports analysts never notice a difference in his game, Cusimano insists the concussion will haunt him forever. It’s happened to other players including David Tanabe, a former defenceman with the Carolina Hurricanes, whose nine-year NHL career was cut short in late 2007 by post-concussion syndrome: “You don’t want to think about having a career-ending head injury. The next thing you know, you’re going in the corner and you’re not playing the game the way it should be played because you’re scared,” he says. “You can’t play hockey unless you’re willing to get into confrontation and you’re willing to take risks. No one can play on eggshells.”

It remains to be seen what kind of player Crosby will be in the future, but one thing seems sure: “Whether Crosby’s doctors say he’s changed or not, he’s going to be changed,” Cusimano says. “No one is left unchanged after they suffer a brain injury.”

There was a time not so long ago when brain injuries sustained in sports were deadly or nearly so because players didn’t wear any protective headgear. The NHL only made helmets mandatory as recently as 1979, and that was 11 years after Winnipeg native Bill Masterton of the Minnesota North Stars collided with two other players and smashed his head on the ice: blood spewed from his nose and ears, and he died two days later at age 29. Considering this, the number one priority of standards organizations and manufacturers who developed those first helmets was to prevent “catastrophic brain injuries,” which include fractured skulls and subdural hematomas. To do this, they relied on measuring and then attenuating “linear acceleration,” the kind of high-energy, up-and-down impact—like when someone falls to the ground—that killed Masterton.

Over the years, helmets have made catastrophic brain injuries among hockey players extraordinarily rare. “As a brain surgeon, I’m very happy that I don’t see those cases anymore,” says Dr. Charles Tator, a senior scientist at Toronto Western Hospital and an acclaimed pioneer of concussion research who will also speak at the upcoming safety summit. The problem, however, is that concussions, which are categorized as “mild traumatic brain injuries,” can be caused by lower-energy impacts rather than catastrophic ones. They are best mitigated by measuring and attenuating “angular acceleration”—the force that causes, say, a boxer’s head to rotate when punched in the jaw.

This fact has been established since the 1950s and ’60s, says Hoshizaki, but no hockey helmet ever developed has taken this measurement into account. The reason angular acceleration hasn’t been factored into helmets is partly because until recently it was largely believed that linear acceleration was an adequate “surrogate” for angular acceleration, so accounting for one would attenuate the other. Hoshizaki and others have only recently shown that in the majority of cases this isn’t true. What’s more, developing a new helmet that accounts for both linear and angular acceleration would literally require rewriting an entire industry—new safety and certification standards would need to be established, and before that, new scientific protocols would have to be developed to inform how exactly this new headgear should look and work.

These challenges have meant that no matter how exceptional helmets have gotten at attenuating linear acceleration, “they’ve had almost no effect on concussion at all,” says Hoshizaki. Recent studies done by the NFL show that even when helmets were improved to better manage linear acceleration, concussions didn’t recede. Helmets have, in effect, gotten really good at preventing one type of brain injury that almost never happens anymore, while ignoring another type that is occurring at epidemic proportions. Adds Hoshizaki, who worked in research and development at Nike Bauer and CCM before becoming director of the U of O’s School of Human Kinetics: “Having more protection for those injuries that don’t occur is not much of a strategy.”

Hoshizaki, who is also the chair of the International Organization for Standardization (ISO) ice hockey product certification committee, has been working on one protocol with his team called the University of Ottawa Test Protocol. UOTP was first developed in 2009, after Hoshizaki helped design the Xenith helmet for football. Already gaining popularity in the NFL, the helmet works by better managing both high and low linear impact. The UOTP will help make future hockey and football helmets even better by measuring both linear and angular accelerations, or 3-D impacts.

The aftershocks

Photograph By Blair Gable

The reconstruction of the hit similar to Crosby’s is a perfect example of that. Hoshizaki and his team use their custom-made mechanical machine called a linear impactor. It measures linear and angular accelerations that occur at six different directions during impact. The nine sensors inside the head form stream data into a computerized brain model containing 7,000 3-D zones that represent all parts of the brain, and indicate tissue stress. This is very different from the current machine used to test hockey helmets, which drops the head form from above to recreate an impact, and features only one sensor inside the dummy, one without a neck.

The next steps for the lab are to determine which parts of the brain are most vulnerable to impact; Hoshizaki and his team hypothesize that some areas have a much lower “threshold” so even though they absorb less energy from the impact, they are more stressed. They also hypothesize that there is a correlation between the location of tissue stress and the types of symptoms that occur.

VIDEO: Hit to the head: a similar one to Sidney Crosby’s (reconstruction)

All of this research promises a dramatic leap forward in the understanding of concussions—and how to manage them. For starters, hockey helmets might get rounder and harder as a way of better attenuating the angular accelerations associated with concussions. The padding inside might be altered to absorb both linear and angular accelerations. Leagues like the NHL would finally know exactly what kinds of hits are most dangerous, and why one blow might sideline a player for months but barely faze another.

And it will help doctors such as those treating Crosby explain to their patients why they are feeling so bad, and how long the agony will last. “Patients ask me all the time: show me where in my brain it’s damaged to produce the dizziness or memory loss or nausea,” says Tator, who is also a professor at the University of Toronto. “We simply don’t know the answer yet to that very fundamental question. But I do think that eventually these important questions will be answered.”

Testimony as to the effect of concussions isn’t hard to come by. From the dazzling centreman Pat LaFontaine, who was knocked cold by a check in 1990, to Stu “the Grim Reaper” Grimson, who once blacked out during a fight, the list of hockey players who lost count of their concussions could make a formidable NHL roster. More disconcerting from Crosby’s perspective, though, may be the experience of players like David Tanabe, whose NHL career can be told as the tale of just two concussions—the one that started it, and the one that ended it.

Tanabe was drafted in the first round by the Carolina Hurricanes in 1999. Blessed with speed and playmaking vision, he was on a fast track to stardom when he stepped from the penalty box into a game against Pittsburgh and took a hit from a passing player that spun him around, sending him to the ice. “I experienced nausea right away,” he recalls. “I went into the locker room disoriented. Within 10 or 15 minutes, I started to experience extreme fatigue.”

He spent 16 hours a day for the next five days sleeping. The blow sidelined him for nearly three weeks. Tanabe returned to play symptom-free, but today wonders whether that was a good idea. “Just because you’ve got your cognitive abilities back doesn’t mean there aren’t other things that haven’t resolved yet,” he says. Even players who have symptoms can pass the baseline tests used to assess their cognitive health, he notes, “and once you’ve had one concussion, you’ve kind of opened the door.”

The next few seasons brought no obvious head injury, but through a nine-year career on three different teams, Tanabe never matched the 29 points he put up in his first full season in Carolina. The influence of his first concussion on his game remains an open question (unsympathetic Carolina fans still gripe that he never lived up to expectations). But there’s no doubt it set him up for the coup de grâce—a seemingly harmless check during a game against Toronto in late 2007 that rapped his head on the glass. This time the symptoms set in slowly. “I couldn’t focus my vision, my eyes felt strained,” Tanabe says. “I’d try to exercise and the symptoms just got worse and worse.”

He went on Carolina’s injured reserve list, and as the weeks sailed by, he sensed his career was in jeopardy. He yearned to play, but his impatience and anxiety only seemed to deepen his symptoms. Something as simple as a trip to a restaurant could overwhelm him, he recalls, sending him home to sleep for days. “Imagine waking up from general anaesthetic, then going for a walk through a crowded shopping mall,” Tanabe says. “That’s what it was like for me to go out in public. People have compared [post-concussion effects] to being drunk. But when you’re drunk, chances are you’re feeling good, and this was not a good feeling.”

Tanabe never got well enough to play. He retired in October 2008. Today he is loath to hear pity. But he says fans, media and players need to understand that the invisible effects of concussion can be every bit as crippling as a broken limb or a torn ligament. Teammates who saw him during his recovery would ask what he’d been doing for the past four months, he recalls, deepening his sense of despair. “Everyone has to step back and recognize that players want to play,” he says. “It should never be a question of a player’s integrity.”

That desire to compete is part of a formula that make professional athletes extra vulnerable to the effects of repeat trauma, say others who have endured it. It’s possible to bar a player from competition, but training is another story. And once an athlete is back, good luck trying to make him play safe.

This was particularly true of Keith Primeau, a six-foot-five, 235-lb. centre with the Philadelphia Flyers whose approach to hockey was defined by sheer will. Primeau suffered four documented concussions before he retired in 2006, and as many as a dozen more that were never recorded. Playing through two concussions during the 2004 playoffs, he turned in one of the most dominant single-player performances of recent memory, literally tilting the game in his team’s favour whenever he climbed over the boards.

VIDEO: Hit to the head: a similar one to Sidney Crosby’s (reconstruction)

“I didn’t let it affect the way I played,” Primeau now says, “and that was part of my downfall. I just couldn’t transform my game from being physical to being a skill guy who was going to handle the puck and go through everybody.” In Primeau’s case, the costs were enormous: long hours spent in his home office, with the blinds shut and the computer turned off to limit sensory input. With each day he couldn’t play, his temper thinned. “My kids were little, but old enough to know that I needed space,” he says. “It was a very dark time. I’m very lucky to have such an understanding wife and family.”

Primeau’s symptoms were maddeningly random, changing from concussion to concussion, before he suffered what proved his last in a game against Montreal in October 2005. He’d feel ready to skate, he recalls, only to find the halogen lights at the Flyers’ practice rink triggered vision problems. Once, in 2000, the computer baseline test intended to determine whether he was fit to play actually caused him a calamitous headache. He had passed the test, and played anyway. But he acknowledges now that “it was the wrong choice.”

Primeau is currently director of player development for a minor-pro team in Las Vegas, and has followed Crosby’s recovery with queasy fascination. The media drumbeat demanding when the young star will return appalls him; in Crosby, Primeau sees the part of him that would happily assume the risk to get back into competition. “I heard somebody the other day questioning whether Pittsburgh should shut down his season, because, you know, it would hurt their chances of winning a Stanley Cup,” Primeau says. “I thought, what a terrible state we’re in when we’re willing to risk someone’s health for the sake of winning a championship. I had that same attitude, and I’m sad to see that mentality hasn’t changed.”

To see what has changed in hockey, one need only watch footage of old games. Or not so old. “The game was played entirely different, even into the ’90s. It’s dramatic, almost shocking,” says Hoshizaki. Nowadays, shifts last 40 seconds, where years ago they would have been two or three times as long. And while bigger, faster players and better equipment have made the game more intense, modern strategies have increased the level of danger, too. Whereas before teams created their own plays by controlling the puck for longer periods of time, today it barely hits a player’s stick before being catapulted elsewhere. Now, Hoshizaki explains, “the strategy is to disrupt the opponent’s game.”

This antagonistic approach plays into the “winning at all cost” culture that Cusimano says is so pervasive in hockey. It’s also what causes people to dismiss arguments for cracking down more seriously and consistently on hits to the head, saying that such measures will take the spirit and integrity out of the sport. And so, herein lies the irony: that the very “love” of the game that keeps leagues from making hockey safer might be the very thing that will damage the sport irreparably.

Already it has lost the honour of being the most popular game among youth, which many speculate is partly due to a growing fear among children and parents about the dangers of hockey. (Tator, who founded the brain injury awareness association ThinkFirst, is advocating a “pre-season team meeting” for concussion education aimed at parents, players and officials.) Cusimano wonders if in 20 years’ time, hockey will be as closely tied to the Canadian national identity as it is today, or whether the leagues will see a slow but steady attrition as more people realize that what happened to Crosby could happen to them or their children.

“One of the things that defines our lives is how our brain works,” says Cusimano. “Why do we want to have sports that damage this precious thing? If you had a $50-million winning lottery ticket, would you skate around the ice with it in between your teeth knowing that maybe you would lose it? Nobody would do that. But we say it’s okay to basically inflict brain injury on people. Even with $50 million, we wouldn’t ever get that back.”

Concussions come at a high price. Just ask Crosby.




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Hits to the head: Scientists explain Sidney Crosby’s concussion

  1. there are many games in the world ,where players must protect their head,like in the hockey,cricket and other games,

    • Your right, many sports require that we respect the potential of head injury. However since hockey is at the forefront in Canada, it's natural it would be our case study.
      The difference is that in hockey and football, player contact is the norm. Without respecting your opponent, you likely will hit them aggressively. Sometimes with the intent of putting them on the bench.
      In the States, the NFL and it's players are faced with similar concerns. Can players be spared life changing trauma without sacrificing the game?

      • I think it has alot to do with the type of hits and the approach of the tackling player. Blindside hits and hits from behind are commonplace in hockey and NFL/CFL. Sports like Rugby and to some extent cricket/baseball the impact is largely from the front so there is an element of preparedness that you don't get in hockey.
        Association football (soccer) has worked hard to try and outlaw tackles from behind because of the vulnerability of the player to serious career ending injury.
        Another aspect of hockey that does not occur in other sports is the acceptance of fighting. It is bad enough with guys feeding each other blow after blow to the head face on. But when you consider the Bertuzzi affair and the terribly cowardly sucker punch that happened in the Penguins/Islanders game the other night it surprises me that there aren't more serious cases of brain injury on a regular basis. A good way to reduce a lot of the head impacts would be to deal more harshly with fighting. Otherwise accept your are going to damage some very good players.

        • Don't forget the speeds of the impacts make a huge difference. Hockey players are moving much faster than someone running on a rugby pitch or football field.

    • 9/11

  2. Is the only way they can get people interested to read it to include Crosby's name on it? Players have been having concussions and having their careers ended by concussions long before he came along.
    If they decide to make some drastic change to the rules because this happened to a single player, what is that telling all the players previous? "Sorry about your luck, but we just didn't think you were important enough to change the rules for you."
    They should have been looking into concussions as soon as the first player had to quit because of them, not because Crosby got one. Either way though, the game will continue on without him.

    • tys give your head a shake, but not a drastic shake because I think you are already concussed, making a stupid comment like that.

    • Tys, the truth of the matter is that the medical community – neurologists in particular – have been busy gathering more and more information about the seriousness of concussions and that is what has brought about the use of helmets in sports like skiing. When the best player in a sport experiences what could be a career-ending injury, it is only normal that there is a wider public interest and journalists respond by writing about it. The NHL has already been looking at these blindside hits and head hits. More pressure has been put upon them now because it is their number one player who is out with the injury but there is no doubt that a change in policy will be beneficial for everyone in the game. Had Wayne Gretzky had a career-ending concussion or Gordie Howe – yes, we probably would have discussed this alot sooner.

    • You Crosby haters are such dinosaurs.

  3. Incomplete scientific knowledge about the brain had led to cruel tragedies for these poor young people–and who knows how many others have suffered equally over the years.

    At least ,we now realize the importance of brain research, and should make it one of the priorities in scientific research funding. There are many other brain solutions waiting to be discovered.

  4. Hits to the head should not only be their main concern. Whiplash itself causes more damage from head to toe and it is more a widespread occurrence.

  5. Great article, compelling video. I recommend that interested parties review a recent comparison of helmet pad technology performed by the Lawrence Livermore National Laboratory. They compared the padding systems of the NFL and the U.S. army in a model of linear acceleration. They determined that the current NFL helmet pads do not provide the same level of protection as the authorized U.S. Army pads. Suffice it to say, rotational accelerations are at issue, however, lets make sure we are using the best protection in our helmets as possible while we continue to work through the research and standard setting on rotational injury prevention. The U.S. army has done great work in this area and can offer significant insight into this issue. I posted a link to the helmet pad comparison on my website at http://www.medsecintl.com. Dr. Matt Evenhouse.

  6. As a concussion victim (2 treated hockey concussions and 1 work related concussion), this article was refreshing. It's time that we gave this injury the respect it deserves. As a farmer and lobbyist, I was effectively confined to the couch in my home for 5 weeks dealing with a relatively minor concussion because too much (read hardly any) activity or concentration wore me out or left me with head pain that would put me down for the rest of the day. The biggest problem is these are invisible injuries and those not suffering from them, can't see what's being felt by the victim. Thank you again Macleans, let's hope the research will continue to move along so that we see an end to these horrible injuries.

  7. The hope, and the anticipated outcome, is that this discussion will also lead to changes in youth sports. Basketball in Alberta and across Canada, for instance, is a "smash-mouth" sport. Extensive contact has become the norm. High impact collisions, hard fouls, submarinings, are becoming common-place, with referees opting to judge calls based on whether or not an advantage was gained, rather than whether or not a rule-infraction occurred. Even in hockey, rules are in place to maintain safety, to foster respect between athletes, to ensure that the drive is to, as Vince Lombardi promoted, "Win. Fairly, squarely, by the rules, but to win!" In many sports, we have drifted away from the rules in favor of the higher intensity, survival of the toughest approach and the apparent excitement it brings.

    In some leagues, basketball is a sport of speed, coordination, power, amazing skill, and finesse. Not so much in Alberta. We could do better, and our kids deserve a safer playing environment. Highly competitive? I hope so. Fast? Winner take all? I hope so. But not at the expense of safety and respect.

    • I totally agree, I put my kids in basketball because it used to be speed finesse skill team play and “no contact”  - not any more .My daughter has suffered 2 concussions now and has to quit a game she loved.  Many of her team mates have had concussions too and should not be playing because they continue to have symptoms still a year after the injury.  

      they need to clean up the sports so that they return to skill speed finesse and not this ridiculously dangerous thing they have become.  We also play bball in Alberta and I am not happy with the way the sport has gone.  Especially at the post secondary level it gets even worse.  Why shouldn’t we be able to play in a safe environment.  YOu can still play very competitive and fast and exciting sports without allowing the contact.   Clean it up, keep it safe.

  8. Look at this simply. When you take a ‘hit’ say in the hand. You get a ‘bruise’ / spilled blood / broken red blood cells. This blood is NORMALLY ‘mined up’. This blood contains the metal iron. When the body doesn’t remove this iron it is deposited in a long term storage form known as hemosiderin to be used when needed. Normally it would be removed. This iron is what is causing the problem as in Parkinson’s , Alzheimer’s and tardive dykinesia and other neurodegenerative diseases like Multiple Sclerosis. Very low iron diet and targeting of the iron in the brain is what is being tested in neurodegenerative disease.
    “Increasing evidence indicates that iron deposition in the brain might play a role in cognitive dysfunction associated with neurodegenerative disorders and aging.”
    “Cognitive declines therapy by iron burden reduction” 
    “Cognitive impairment is associated with subcortical magnetic resonanceimaging grey matter T2 hypointensity in multiple sclerosis”
    “Iron chelators that can cross the blood-brain barrier may have thepotential to treat cases where abnormal iron accumulation in the brainis associated with the degenerative processes”

  9. i took a hit from a car going 55mph on my motorcycle head on head. no ones fussing about my head injury. i cant even get ssi

  10. It just figures the medical profession is skeptical. They always are it seems if a cure doesn’t involve expensive drugs/longterm treatments. Kudos to the Canadian-born Carrick & his motto …”seek wisdom” … “because it is something (he) has always ascribed to.”

  11. maybe it`s time to start looking into Brain pad dual arch mouth guards. Clench and breath is the way of the future for contact sport…

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