How Reebok Is Tackling One Of The Sports World’s Trickiest Problems

With a concussion-busting skullcap, Reebok is on a quest to mitigate head injuries in young athletes.


When representatives from Reebok and the electronics design firm MC10, both based near Boston, began looking for a youth sports team to test out their concussion-detecting monitor, they started in their own backyard. The Checklight–a black skullcap embedded with sensors that are optimized to detect dangerous ­impacts–represented thousands of hours of research and collaboration, and neither partner knew how it would be received, or even how well it would work. They wanted to start small.


In 2012, they approached Brian Costello, coach of the Wayland–Weston Warriors, a youth football team based in the Massachusetts suburb where MC10’s director of sports, Isaiah Kacyvenski, lives. Costello was skeptical. “There’s no technology that’s going to prevent anyone out there from getting hit in the head,” he says. But he was concerned enough about concussions that he thought the device was worth trying.

Costello’s players loved the idea. Many of them wore skullcaps (close- fitting head coverings) under their helmets anyway, and the fact that they were the only football team in the league–in the world–to get the monitors made them feel special. What’s more, the Checklight was simple: comfortable and snug, with a small tail that dangled just below the base of the helmet. At the end of the tail was an LED light. Green under normal circumstances, it would flash yellow or red should sensors detect a stronger-than-normal impact. It would only turn green again after being reset by a coach.

Checklight’s value became clear early in the season when a 13-year-old player made a fairly innocuous-looking tackle of the opposing quarterback. He popped right up, feeling no pain or anything more than a “slight buzz” in his head. Had he not been wearing a Checklight, he’d probably have played on. But his light was flashing yellow, so the kid came out of the game. Soon after, he began to experience concussion symptoms and ultimately missed three weeks of football. If he had kept playing, the injury could have been far worse.

Some 250,000 young athletes end up in the emergency room for serious head injuries every year, according to the National Academy of Sciences, and that number is almost certainly low due to how difficult concussions are to detect. Symptoms sometimes don’t appear until hours after the injury, and playing with an undiagnosed concussion is especially dangerous. Subsequent blows can lead to brain swelling and even death. “We can’t solve the problem,” says Robert Cantu, a neurosurgeon, concussion expert, and cofounder of the Sports Legacy Institute, which collects and studies the brains of deceased athletes suspected of suffering from brain injuries. “We can mitigate it.”

Better helmets, improved technique, and rule changes are being implemented across contact sports at all levels in an effort to reduce the incidence and severity of concussions, but increasingly, companies like Reebok and MC10 are using technology to come up with defensive tactics of their own. Checklight won’t cure concussions. But it might save lives.


Concussions became a hot-button issue across contact sports in 2008 after research suggested a connection between repeated head injuries and debilitating mental conditions, especially chronic traumatic encephalopathy. Helmets were originally made to prevent major head trauma, in particular skull fractures, and they did that well. But they weren’t so good at preventing concussions. Reebok made helmets and protective gear for several pro sports leagues. And Paul Litchfield, who for 23 years had led the Reebok Advanced Concepts group (RAC)–a quasi–black ops unit for innovation and whimsy–wanted to see if his team could address the concussion problem via design.

Litchfield, 53, is thin and pale with a shaved head. Wearing an untucked boston pd intelligence unit T-shirt that is at least a size too big, and making frequent use of the adjective wicked, he recalls how his first notion was to insert some kind of cushioning to decelerate the force of impact. But he and his chief collaborator, Paul Davis–a lanky fellow with a ponytail who studied sculpture at RISD before finding his way to industrial design–realized that while they could address direct linear impacts, collisions in a game don’t tend to arrive in a straight line. There are multidirectional forces in all hits, causing the head to buck and twist on the neck, as well as bounce around within a helmet. The solution wasn’t a better helmet, they decided. It was something that could quantify and detect severe collisions. “So we transitioned into this exploration of how to assess impact,” he says.

Others had a similar idea. In 2007, Riddell, the NFL’s primary helmet maker, had installed sensors that transmitted data to devices on the sideline for interpretation. Called IQ HITS, the system was tested by several major college-football teams, but each helmet cost more than $1,000 and required trainers to monitor and interpret data. This seemed overly complicated to Litchfield, and he was also concerned about the location of the sensors. Helmets are not attached to the head, so their movements don’t necessarily correlate to movement of the brain inside the skull.

Reebok’s Paul LitchfieldIllustration: Kervin Brisseaux

In 2009, a friend introduced Litchfield to a tiny startup based in Cambridge, Massachusetts, called MC10. The technology company was developing flexible, conformable electronics based around stretchable circuits that had been invented by a University of Illinois professor named John Rogers. MC10’s first prototype was an electronic sensor that adhered to skin. The best way to measure impact, Litchfield realized, was to put the detection device directly on the head, and he knew that RAC, using MC10’s go-anywhere sensors, could probably find a way to do that. This strategy would also mean that Reebok could offer a single product for every sport; if somebody played hockey and snowboarded, the device could detect impacts in both situations.

In an office at the RAC headquarters in Canton, Massachusetts, Litchfield–who’s best known for inventing the Pump for Reebok sneakers–shows me one clunky plastic ­prototype after another, early iterations that involved stuffing cheap sensors into boxes held on via headbands and straps. “It was a series of stepping stones,” he says. At the end of that path was the Checklight.


The device, which went on sale to the public in July 2013 and retails for $150, is so lightweight that it feels no different from any other skullcap. But inside is a thin, pliable band of sensors encased in a strip about as thick as a stick of gum. The two most critical sensors are an accelerometer, which measures linear motion, and a gyroscope, which detects rotational forces. When the Checklight perceives a blow, those areas activate and measure both the initial impact and what Litchfield calls “the aftershock effect,” when the head ­continues to bounce and shake in the following milliseconds. An onboard microprocessor analyzes that information instantaneously and, based on its calculation, causes the light to change or stay green.

A red light doesn’t mean the wearer has a concussion, necessarily; it just suggests the person sustained an impact that could lead to one. “This is not a predictor of injury,” Litchfield says, nor is it a diagnostic tool. He pauses to make sure I have absorbed that critical point. The goal of Checklight is to “take the guesswork out of head impact,” he says. “You know when you bust your knee. You know when you are cut. But how hard have you hit your head? We wanted to create a fact-based identifier where we go, ‘You received this impact, and it is in this range, so get yourself checked out.’ ”

Isaiah Kacyvenski is built like a refrigerator. He was a football star at Harvard, then went on to play linebacker for eight years in the NFL–a period in which he had seven concussions. “Those were just the ones diagnosed,” he says, sitting across a conference table in MC10’s offices. When injuries ended his career, Kacyvenski got his MBA at Harvard and joined MC10 as employee No. 14. He was placed immediately on the program that became Checklight, alongside director of product development Steven ­Fastert, who serves as co-lead on the project.

Detecting a potential concussion might seem simple–big blow equals possible injury–but it turns out to be quite complicated. There is no “magic number for concussions,” Kacyvenski says–meaning some measure of g-forces beyond which a brain injury definitely occurs. What he and Fastert did, however, was “put data points where they’ve never been before,” to take some of the mystery out of, ‘How hard was I hit?’ ”

MC10’s Isaiah KacyvenskiIllustration: Kervin Brisseaux


“We’re giving a lot of unbelievably complex infor­mation,” Kacyvenski continues: “linear acceleration in three different planes and radians-per-second for the rotation and acceleration,” plus a large quantity of data gathered from published studies, biomechanical research, 15,000 drop tests in Reebok’s lab, and field tests. All that high-level computation is hidden from users, as it must be if you want to make it useful for the general public. “We’ve taken that massive body of data and crammed it down to give you a light trigger on the end that is actionable.”

Across the table, Fastert smiles proudly. “It’s the opposite of big data,” he says. “It’s small data.”

For now. The first iteration of Checklight is a closed system; it doesn’t have wireless capability, so in order to extract its data, coaches need to plug it into a smartphone, tablet, or computer. Reebok is encouraging trainers who work with Checklight teams to share data with CSMI, an information technology company that has agreed to track impact-related data from willing participants (individual data remains confidential). “The quantification of hits in a way that doesn’t cost [researchers] a huge amount of money is really going to inform the science,” says Cori Lathan, founder and president of Anthro­Tronix, which makes a digital tool for the military that tests for neurocognitive damage caused by head injury. “What are the hits? How do they correlate to symptoms and patient profiles?” On the most tangible level, the Checklight and other impact sensors that are trickling out to market (see sidebar, left) could help assess which new sports rules are effective in reducing the kinds of hits that cause head injuries. More broadly, they have the potential for delivering greater understanding not only of concussions but the brain itself.

Safety innovations often catch on slowly. As Litchfield points out, it took years before seat belts and bike helmets were widely accepted; today, you look crazy for not using them. Checklight has not yet been widely adopted, though it’s only been on sale for around a year. The line expanded in August, when a headband version arrived, opening the market especially to girls’ soccer, which trails only football and boys’ hockey in the rate of concussions.


There are signs of progress. Something surprising happened with the Wayland–Weston Warriors over the course of last season. Reebok and MC10 tracked info from the sensors and noticed that the number of red and yellow lights players incurred dropped dramatically (by 85% and 50%, respectively). Coach Costello can’t explain it but suggests that wearing a Checklight influenced players’ behavior; they were actively trying to avoid head impacts that might set off the lights. “I think one of the bigger benefits has nothing to do with technology but everything to do with kids ­having blinking lights on their heads as a constant reminder of, ‘Hey, hits to the head are really important to avoid.’ ” Which Litchfield and Kacyvenski find especially exciting. “The kids realize the whole point is that you don’t want to get hit. You don’t want to trigger the light,” Kacyvenski told me.

Litchfield says that during the Checklight’s five- year development, he was often asked whether players in the macho, slow-to-evolve culture of the NFL might one day wear one. “Not now,” he said. “It will start with kids. But, eventually, down the line–yes. Everyone will wear something like this.”

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About the author

Josh Dean is a magazine writer based in Brooklyn and the author of Show Dog. Find him on the web ( or on Twitter @joshdean66.