Accelerometers could finally fix the NFL's concussion crisis

Tears streamed down Luke Kuechly’s face as he sat on the turf. Nothing about the the Carolina Panthers linebacker’s fourth-quarter collision with New Orleans Saints running back Tim Hightower seemed especially gruesome—that Thursday night game in November had seen much harder hits, and more would follow in the six weeks of season left. But the longer the former defensive player of the year stayed down, TV cameras lingering on his slumped form, the clearer it became that something was seriously wrong. Kuechly left the field on a cart, and once again, the NFL’s concussion crisis became impossible to ignore.

The link between repeated concussions and degenerative brain diseases like chronic traumatic encephalopathy is strong enough for the NFL to have settled a $760 million class-action suit with retired players in 2014. Current policy calls for any player showing concussion symptoms to be benched until they pass tests for cognition, balance, coordination, and neck mobility. But even the most thorough sideline test would fail to identify what Robert C. Cantu, co-founder of Boston University’s CTE Center, calls “the elephant in the room”: sub-concussive events. Though less dramatic than high-grade concussions, these impacts still destroy neurons, and can occur many times per game—piling on additional long-term damage with each hit.

As the world tuned in to Super Bowl LI on Sunday, the NFL is again on a global stage. Yet, in an era of billion-dollar broadcast deals and 4K cameras, it’s still impossible to see just what kind of hits lead to brain injuries. Concussion remains largely a “hidden injury,” as the New York Times called it in 1998. But according to Timothy Gay, a physicist from University of Nebraska–Lincoln, it doesn’t have to be. “If we could get the players to allow accelerometers in helmets, we could measure the forces on a broad epidemiological basis,” he says.

The Makings of a Movement
Once the province of missiles and aircrafts, accelerometers are now in everything from cars (to deploy airbags) to smartphones (to signal when to rotate the screen). Gay believes that if every NFL helmet had an accelerometer, researchers could find correlations between force, angle of hits, and incidence of concussion.

The idea isn’t new. Riddell, the NFL’s official helmet manufacturer, began working with built-in accelerometer technology in 2004. According to Thad Ide, Riddell’s senior vice president of research and product development, the technology has been used in research over the last decade at the youth, high school, and collegiate level. Riddell currently sells a helmet carrying a pad loaded with a collection of accelerometers and motion sensors paired with a processor and transmitter. The helmet measures the magnitude of impact, as well as the location, direction, and duration of the hit, sending the information back to a computer on the sideline. The entire tracking system, sold as the Riddell Sideline Response System, is currently being used at over 20 research institutions, including Virginia Tech and UCLA.

This season, University of Texas’s football team used an upgraded version of Riddell’s technology in all its games and practices: The system, called InSite, automatically processes all collision data, and alerts the coaches when a single hit, or a collection of hits, exceeds a head-impact threshold. “InSite actually alerts the sidelines based on certain levels of impact and probabilities of a player potentially suffering a head injury,” Ide says. “It’s an extra piece of information and an extra set of eyes on the field that they wouldn’t otherwise have.”

In 2013, two unnamed NFL franchises participated in a voluntary pilot program of in-helmet accelerometer technology—neuroscientist Kevin Guskiewicz of the University of North Carolina told the New York Times that the program collected data on more than 11,000 impacts. However, the league eventually suspended the program, claiming that the sensors couldn’t deliver reliable data. Brian McCarthy, the NFL’s vice president of communications, says that the NFL remains hopeful that it can one day reinstate the accelerometer program. “We want to get to a point where everyone is comfortable with the technology, where everyone is comfortable with the science, with the shared goal of improving player safety,” he says.

But the disputed data has already led to on-field rule changes. Guskiewicz’s pilot-program research identified kickoff returns as the plays with the highest risk of impact. His presentation to the league in 2011, supported by information collected from in-helmet accelerometers, proved compelling enough for the competition committee to move the kickoff line five yards forward, to the 35-yard-line. The goal was in part to shorten the running start afforded to the defensive players, and in part to result in more touchbacks, in which the kicked ball sails into or past the end zone and the play is called dead. The impact was immediate: Between 2010 and 2015, the percentage of kickoffs returned was cut in half. McCarthy highlights the kickoff rule change as one of the 42 changes related to player health and safety “in the last dozen years or so.”

More Transparency, More Problems?
While you might think athletes themselves would be in favor of in-helmet accelerometers, the NFL Players’ Association is also balking at the technology. One representative of the union, who hadn’t been granted permission to speak on the record, said that at the time of the pilot program, NFLPA engineers believed the data was too unreliable to be scientifically valuable. According to the source, when reliable accelerometer technology does become available, the union will reconsider the program.

Gay, though, speculates that players’ concerns might instead be rooted in data privacy—and the financial consequences of newfound transparency. “No player wants that kind of data out there when they go to renegotiate their contract,” he says. “Because the team is going to say, ‘Look, you’ve had three big hits in the last year and we’re just worried you’re coming to the end of your rope.’” Indeed, in October 2015 the union halted the collection of off-field sleep data. The NFLPA would continue to fight, the source says, to make sure players retain control of their medical and health information.

For most medical research, personal healthcare data is delinked from patient identity. But in the case of NFL accelerometer data, true anonymity is much more difficult. “Because you have a smaller number of players and a smaller number of circumstances, it can be really hard to deidentify information and still have it be useful,” says Michael McChrystal, a professor of privacy law at Marquette University. There’s also, he adds, a burden of granularity: “Are there different concussion issues for linemen than there are for the skill players? It could be a really tricky problem from a research point of view.”

But the potential public good remains pressing. While fewer than 1,700 players are in the NFL at any moment, the professional league is fed by millions of college, high school, and youth football players. A robust dataset, collected over years, could begin to uncover specifically dangerous plays, degrees of force, or tackling styles, and lead to changes that affect player safety at all levels—like Guskiewicz’s research with the kickoff line, which was subsequently adopted by the NCAA. However, without that transparency, then short of prohibition, it’s unclear exactly how to make it safe enough to play. And for the most lucrative sports league on earth, that’s just not good enough.