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Stanford Investigates the Hits that Cause Concussions

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It's no secret that concussions are endemic in American football at every level, from pewees to the pros, but little is known about the hits that cause them. Stanford University is searching for answers by meticulously gathering data on every impact their football players sustain. The study is only in it's second year, but they've already made some interesting discoveries.

David Camarillo is a bio-engineer at Stanford and a lead researcher on the project. He says “injury research is a tough thing to do because you usually see it only after it happens.” To see brain trauma in real time, Camarillo and his team have outfitted the football team with mouth guards that measure the physics of every hit. At practices, they use ultra-high-definition, slow-motion cameras to observe those collisions more closely and look for ways to prevent them.

Mouth Guards with sensors
Mouth Guards with sensors

The first startling discovery of the research is how little is known about the “injury mechanism” for concussions, that is, exactly how they are caused. People have long associated “getting your bell rung” with a hard hit, or a series of repeated impacts, but little data has been gathered on the nature of those hits. How hard does a hit need to be to cause a concussion outright? How many small, low-impact hits before a player begins to exhibit concussion symptoms?

The definition of a concussion is a fairly simple one: the damage caused when the brain smashes against the inside of the skull. They can come from one hard impact, or repeated low-speed hits. In the short term they cause things like dizziness and loss of memory; in the long-term they can cause severe neurodegeneration. But the diagnosis process for concussions is complex. Symptoms vary widely from player to player and can be easily lied about.

Scott Anderson is the head athletic trainer at Stanford and he's helping to develop the mouth guard prototypes. He says right now there's no good way to analyze and diagnose concussions. With an injury like a sprained ankle or broken rib, a physician can use an MRI or an X-ray to look at the problem. With a concussion there's no way to peer inside the brain and see what's going on. “We can send you for a CT scan to look at your brain,” he says, “but your brain doesn't show us anything.” Instead, physicians have to rely on players to describe symptoms, and players can be highly unreliable.


In a recent survey by Sporting News, more than half the players polled said they would hide symptoms to keep playing, and for good reason. A concussion can cost you your starting spot or, in the case of Greg McElroy of the Jets, your moment to shine .

Alex Smith of the 49ers learned the job-threatening implications of a concussion the hard way. When a concussion sidelined him earlier this season, the replacement quarterback Colin Kaepernick played well and took over his starting role. Now Kaepernick is flourishing while Smith watches from the bench.

With the mouth guards there's no hiding or lying about hits. The team wears the mouth guards at all games and practices so that researchers can generate a comprehensive database of every impact they sustain. The sensors measure linear and angular acceleration—how fast the head is moving in one direction and rotating. The sensors may sound high tech, but actually, you might have some in your pocket right now. They are the same ones used in the iPhone 5.

Camarillo says the mouth guards have already captured some startlingly hard hits, like the one that ended the season for a wide receiver. That collision registered an acceleration of 150 Gs, that's 150 times the acceleration gravity. “Pretty serious business,” he says, “a standard boxing punch is probably between 10-20 Gs.

That's just acceleration in one direction. The player's head was also spinning at 2000 degrees per second—which means his head would have rotated five and a half times in one second if it weren't anchored to the neck. While it has long been suspected that this kind of angular acceleration plays a role in concussions, Camarillo says no one has gathered data on it. What's more disturbing is that angular acceleration has been completely ignored when it comes to football safety measures.

The standard industry lab test for helmets is basically a plunger that smashes a helmet down onto a hard surface. The test hasn't changed much since it was first developed back in 1973 by NOCSAE, The National Operating Committee on Standards for Athletic Equipment. The test doesn't account for angular acceleration at all. “The device,” Camarillo says, “doesn't have any kind of neck.”

A number of research groups are conducting similar studies by putting sensors in the helmets but athletic trainer Anderson argues that the mouth guards give more accurate results. He says the initial data has already revealed something new. Some hits they used to consider as just one are actually two successive collisions. The player has an initial impact during a tackle but the brain receives trauma again when the head collides with the ground. Anderson says the double hit is generating more concussion impacts than a single hit.

Senior fullback Ryan Hewitt
Senior fullback Ryan Hewitt

For the freshmen players, Camarillo and his fellow researchers will be able to gather five years of data. He doesn't expect players at Stanford to have long-term damages if they just play at the collegiate level. But if brain problems begin to show up years down the road, the research team will have accurate records of the impacts they received playing college football.

The success of this study relies on a collaborative effort with a number of different departments at Stanford. Anderson says it's an unprecedented time of cooperation between the sports department, various research groups, and the players. Senior Fullback Ryan Hewitt says he's happy to be part of the study, even though he and his fellow players are “sort of the guinea pigs.” “I figure we might as well use someone,” he says, “and why not use us.” Hewitt hopes the data will help researchers figure out a little more about why concussions happen and eventually develop ways to prevent them.

Camarillo says it's going to take a long time to get any answers to those questions. Even with a big pool of data, he thinks it will be five to ten years before they can even begin to crack what causes concussions.


* The US Senate has organized a committee to conduct an in-depth study on sports-related concussions. They will be having their first meeting on Monday, January 7th.

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